Merge "OpenJDK11: Required files for java.net merging."
diff --git a/api/current.txt b/api/current.txt
index 237d049c..fa86b34 100755
--- a/api/current.txt
+++ b/api/current.txt
@@ -17016,6 +17016,8 @@
     method public static <T> java.util.stream.Collector<T,?,java.lang.Double> averagingLong(java.util.function.ToLongFunction<? super T>);
     method public static <T, A, R, RR> java.util.stream.Collector<T,A,RR> collectingAndThen(java.util.stream.Collector<T,A,R>, java.util.function.Function<R,RR>);
     method public static <T> java.util.stream.Collector<T,?,java.lang.Long> counting();
+    method public static <T, A, R> java.util.stream.Collector<T,?,R> filtering(java.util.function.Predicate<? super T>, java.util.stream.Collector<? super T,A,R>);
+    method public static <T, U, A, R> java.util.stream.Collector<T,?,R> flatMapping(java.util.function.Function<? super T,? extends java.util.stream.Stream<? extends U>>, java.util.stream.Collector<? super U,A,R>);
     method public static <T, K> java.util.stream.Collector<T,?,java.util.Map<K,java.util.List<T>>> groupingBy(java.util.function.Function<? super T,? extends K>);
     method public static <T, K, A, D> java.util.stream.Collector<T,?,java.util.Map<K,D>> groupingBy(java.util.function.Function<? super T,? extends K>, java.util.stream.Collector<? super T,A,D>);
     method public static <T, K, D, A, M extends java.util.Map<K, D>> java.util.stream.Collector<T,?,M> groupingBy(java.util.function.Function<? super T,? extends K>, java.util.function.Supplier<M>, java.util.stream.Collector<? super T,A,D>);
@@ -17048,6 +17050,10 @@
     method public static <T, K, U> java.util.stream.Collector<T,?,java.util.Map<K,U>> toMap(java.util.function.Function<? super T,? extends K>, java.util.function.Function<? super T,? extends U>, java.util.function.BinaryOperator<U>);
     method public static <T, K, U, M extends java.util.Map<K, U>> java.util.stream.Collector<T,?,M> toMap(java.util.function.Function<? super T,? extends K>, java.util.function.Function<? super T,? extends U>, java.util.function.BinaryOperator<U>, java.util.function.Supplier<M>);
     method public static <T> java.util.stream.Collector<T,?,java.util.Set<T>> toSet();
+    method public static <T> java.util.stream.Collector<T,?,java.util.List<T>> toUnmodifiableList();
+    method public static <T, K, U> java.util.stream.Collector<T,?,java.util.Map<K,U>> toUnmodifiableMap(java.util.function.Function<? super T,? extends K>, java.util.function.Function<? super T,? extends U>);
+    method public static <T, K, U> java.util.stream.Collector<T,?,java.util.Map<K,U>> toUnmodifiableMap(java.util.function.Function<? super T,? extends K>, java.util.function.Function<? super T,? extends U>, java.util.function.BinaryOperator<U>);
+    method public static <T> java.util.stream.Collector<T,?,java.util.Set<T>> toUnmodifiableSet();
   }
 
   public interface DoubleStream extends java.util.stream.BaseStream<java.lang.Double,java.util.stream.DoubleStream> {
diff --git a/ojluni/src/main/java/java/util/stream/Collectors.java b/ojluni/src/main/java/java/util/stream/Collectors.java
index a338ec2..26d98bf 100644
--- a/ojluni/src/main/java/java/util/stream/Collectors.java
+++ b/ojluni/src/main/java/java/util/stream/Collectors.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -27,7 +27,6 @@
 import java.util.AbstractMap;
 import java.util.AbstractSet;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
@@ -66,36 +65,37 @@
  * common mutable reduction tasks:
  *
  * <pre>{@code
- *     // Accumulate names into a List
- *     List<String> list = people.stream().map(Person::getName).collect(Collectors.toList());
+ * // Accumulate names into a List
+ * List<String> list = people.stream()
+ *   .map(Person::getName)
+ *   .collect(Collectors.toList());
  *
- *     // Accumulate names into a TreeSet
- *     Set<String> set = people.stream().map(Person::getName).collect(Collectors.toCollection(TreeSet::new));
+ * // Accumulate names into a TreeSet
+ * Set<String> set = people.stream()
+ *   .map(Person::getName)
+ *   .collect(Collectors.toCollection(TreeSet::new));
  *
- *     // Convert elements to strings and concatenate them, separated by commas
- *     String joined = things.stream()
- *                           .map(Object::toString)
- *                           .collect(Collectors.joining(", "));
+ * // Convert elements to strings and concatenate them, separated by commas
+ * String joined = things.stream()
+ *   .map(Object::toString)
+ *   .collect(Collectors.joining(", "));
  *
- *     // Compute sum of salaries of employee
- *     int total = employees.stream()
- *                          .collect(Collectors.summingInt(Employee::getSalary)));
+ * // Compute sum of salaries of employee
+ * int total = employees.stream()
+ *   .collect(Collectors.summingInt(Employee::getSalary));
  *
- *     // Group employees by department
- *     Map<Department, List<Employee>> byDept
- *         = employees.stream()
- *                    .collect(Collectors.groupingBy(Employee::getDepartment));
+ * // Group employees by department
+ * Map<Department, List<Employee>> byDept = employees.stream()
+ *   .collect(Collectors.groupingBy(Employee::getDepartment));
  *
- *     // Compute sum of salaries by department
- *     Map<Department, Integer> totalByDept
- *         = employees.stream()
- *                    .collect(Collectors.groupingBy(Employee::getDepartment,
- *                                                   Collectors.summingInt(Employee::getSalary)));
+ * // Compute sum of salaries by department
+ * Map<Department, Integer> totalByDept = employees.stream()
+ *   .collect(Collectors.groupingBy(Employee::getDepartment,
+ *                                  Collectors.summingInt(Employee::getSalary)));
  *
- *     // Partition students into passing and failing
- *     Map<Boolean, List<Student>> passingFailing =
- *         students.stream()
- *                 .collect(Collectors.partitioningBy(s -> s.getGrade() >= PASS_THRESHOLD));
+ * // Partition students into passing and failing
+ * Map<Boolean, List<Student>> passingFailing = students.stream()
+ *   .collect(Collectors.partitioningBy(s -> s.getGrade() >= PASS_THRESHOLD));
  *
  * }</pre>
  *
@@ -116,21 +116,69 @@
             = Collections.unmodifiableSet(EnumSet.of(Collector.Characteristics.UNORDERED,
                                                      Collector.Characteristics.IDENTITY_FINISH));
     static final Set<Collector.Characteristics> CH_NOID = Collections.emptySet();
+    static final Set<Collector.Characteristics> CH_UNORDERED_NOID
+            = Collections.unmodifiableSet(EnumSet.of(Collector.Characteristics.UNORDERED));
 
     private Collectors() { }
 
     /**
-     * Returns a merge function, suitable for use in
-     * {@link Map#merge(Object, Object, BiFunction) Map.merge()} or
-     * {@link #toMap(Function, Function, BinaryOperator) toMap()}, which always
-     * throws {@code IllegalStateException}.  This can be used to enforce the
-     * assumption that the elements being collected are distinct.
+     * Construct an {@code IllegalStateException} with appropriate message.
      *
-     * @param <T> the type of input arguments to the merge function
-     * @return a merge function which always throw {@code IllegalStateException}
+     * @param k the duplicate key
+     * @param u 1st value to be accumulated/merged
+     * @param v 2nd value to be accumulated/merged
      */
-    private static <T> BinaryOperator<T> throwingMerger() {
-        return (u,v) -> { throw new IllegalStateException(String.format("Duplicate key %s", u)); };
+    private static IllegalStateException duplicateKeyException(
+            Object k, Object u, Object v) {
+        return new IllegalStateException(String.format(
+            "Duplicate key %s (attempted merging values %s and %s)",
+            k, u, v));
+    }
+
+    /**
+     * {@code BinaryOperator<Map>} that merges the contents of its right
+     * argument into its left argument, throwing {@code IllegalStateException}
+     * if duplicate keys are encountered.
+     *
+     * @param <K> type of the map keys
+     * @param <V> type of the map values
+     * @param <M> type of the map
+     * @return a merge function for two maps
+     */
+    private static <K, V, M extends Map<K,V>>
+    BinaryOperator<M> uniqKeysMapMerger() {
+        return (m1, m2) -> {
+            for (Map.Entry<K,V> e : m2.entrySet()) {
+                K k = e.getKey();
+                V v = Objects.requireNonNull(e.getValue());
+                V u = m1.putIfAbsent(k, v);
+                if (u != null) throw duplicateKeyException(k, u, v);
+            }
+            return m1;
+        };
+    }
+
+    /**
+     * {@code BiConsumer<Map, T>} that accumulates (key, value) pairs
+     * extracted from elements into the map, throwing {@code IllegalStateException}
+     * if duplicate keys are encountered.
+     *
+     * @param keyMapper a function that maps an element into a key
+     * @param valueMapper a function that maps an element into a value
+     * @param <T> type of elements
+     * @param <K> type of map keys
+     * @param <V> type of map values
+     * @return an accumulating consumer
+     */
+    private static <T, K, V>
+    BiConsumer<Map<K, V>, T> uniqKeysMapAccumulator(Function<? super T, ? extends K> keyMapper,
+                                                    Function<? super T, ? extends V> valueMapper) {
+        return (map, element) -> {
+            K k = keyMapper.apply(element);
+            V v = Objects.requireNonNull(valueMapper.apply(element));
+            V u = map.putIfAbsent(k, v);
+            if (u != null) throw duplicateKeyException(k, u, v);
+        };
     }
 
     @SuppressWarnings("unchecked")
@@ -203,8 +251,8 @@
      *
      * @param <T> the type of the input elements
      * @param <C> the type of the resulting {@code Collection}
-     * @param collectionFactory a {@code Supplier} which returns a new, empty
-     * {@code Collection} of the appropriate type
+     * @param collectionFactory a supplier providing a new empty {@code Collection}
+     *                          into which the results will be inserted
      * @return a {@code Collector} which collects all the input elements into a
      * {@code Collection}, in encounter order
      */
@@ -233,6 +281,26 @@
     }
 
     /**
+     * Returns a {@code Collector} that accumulates the input elements into an
+     * <a href="../List.html#unmodifiable">unmodifiable List</a> in encounter
+     * order. The returned Collector disallows null values and will throw
+     * {@code NullPointerException} if it is presented with a null value.
+     *
+     * @param <T> the type of the input elements
+     * @return a {@code Collector} that accumulates the input elements into an
+     * <a href="../List.html#unmodifiable">unmodifiable List</a> in encounter order
+     * @since 10
+     */
+    @SuppressWarnings("unchecked")
+    public static <T>
+    Collector<T, ?, List<T>> toUnmodifiableList() {
+        return new CollectorImpl<>((Supplier<List<T>>) ArrayList::new, List::add,
+                                   (left, right) -> { left.addAll(right); return left; },
+                                   list -> (List<T>)List.of(list.toArray()),
+                                   CH_NOID);
+    }
+
+    /**
      * Returns a {@code Collector} that accumulates the input elements into a
      * new {@code Set}. There are no guarantees on the type, mutability,
      * serializability, or thread-safety of the {@code Set} returned; if more
@@ -249,11 +317,47 @@
     public static <T>
     Collector<T, ?, Set<T>> toSet() {
         return new CollectorImpl<>((Supplier<Set<T>>) HashSet::new, Set::add,
-                                   (left, right) -> { left.addAll(right); return left; },
+                                   (left, right) -> {
+                                       if (left.size() < right.size()) {
+                                           right.addAll(left); return right;
+                                       } else {
+                                           left.addAll(right); return left;
+                                       }
+                                   },
                                    CH_UNORDERED_ID);
     }
 
     /**
+     * Returns a {@code Collector} that accumulates the input elements into an
+     * <a href="../Set.html#unmodifiable">unmodifiable Set</a>. The returned
+     * Collector disallows null values and will throw {@code NullPointerException}
+     * if it is presented with a null value. If the input contains duplicate elements,
+     * an arbitrary element of the duplicates is preserved.
+     *
+     * <p>This is an {@link Collector.Characteristics#UNORDERED unordered}
+     * Collector.
+     *
+     * @param <T> the type of the input elements
+     * @return a {@code Collector} that accumulates the input elements into an
+     * <a href="../Set.html#unmodifiable">unmodifiable Set</a>
+     * @since 10
+     */
+    @SuppressWarnings("unchecked")
+    public static <T>
+    Collector<T, ?, Set<T>> toUnmodifiableSet() {
+        return new CollectorImpl<>((Supplier<Set<T>>) HashSet::new, Set::add,
+                                   (left, right) -> {
+                                       if (left.size() < right.size()) {
+                                           right.addAll(left); return right;
+                                       } else {
+                                           left.addAll(right); return left;
+                                       }
+                                   },
+                                   set -> (Set<T>)Set.of(set.toArray()),
+                                   CH_UNORDERED_NOID);
+    }
+
+    /**
      * Returns a {@code Collector} that concatenates the input elements into a
      * {@code String}, in encounter order.
      *
@@ -333,9 +437,11 @@
      * {@code partitioningBy}.  For example, given a stream of
      * {@code Person}, to accumulate the set of last names in each city:
      * <pre>{@code
-     *     Map<City, Set<String>> lastNamesByCity
-     *         = people.stream().collect(groupingBy(Person::getCity,
-     *                                              mapping(Person::getLastName, toSet())));
+     * Map<City, Set<String>> lastNamesByCity
+     *   = people.stream().collect(
+     *     groupingBy(Person::getCity,
+     *                mapping(Person::getLastName,
+     *                        toSet())));
      * }</pre>
      *
      * @param <T> the type of the input elements
@@ -358,12 +464,112 @@
     }
 
     /**
+     * Adapts a {@code Collector} accepting elements of type {@code U} to one
+     * accepting elements of type {@code T} by applying a flat mapping function
+     * to each input element before accumulation.  The flat mapping function
+     * maps an input element to a {@link Stream stream} covering zero or more
+     * output elements that are then accumulated downstream.  Each mapped stream
+     * is {@link java.util.stream.BaseStream#close() closed} after its contents
+     * have been placed downstream.  (If a mapped stream is {@code null}
+     * an empty stream is used, instead.)
+     *
+     * @apiNote
+     * The {@code flatMapping()} collectors are most useful when used in a
+     * multi-level reduction, such as downstream of a {@code groupingBy} or
+     * {@code partitioningBy}.  For example, given a stream of
+     * {@code Order}, to accumulate the set of line items for each customer:
+     * <pre>{@code
+     * Map<String, Set<LineItem>> itemsByCustomerName
+     *   = orders.stream().collect(
+     *     groupingBy(Order::getCustomerName,
+     *                flatMapping(order -> order.getLineItems().stream(),
+     *                            toSet())));
+     * }</pre>
+     *
+     * @param <T> the type of the input elements
+     * @param <U> type of elements accepted by downstream collector
+     * @param <A> intermediate accumulation type of the downstream collector
+     * @param <R> result type of collector
+     * @param mapper a function to be applied to the input elements, which
+     * returns a stream of results
+     * @param downstream a collector which will receive the elements of the
+     * stream returned by mapper
+     * @return a collector which applies the mapping function to the input
+     * elements and provides the flat mapped results to the downstream collector
+     * @since 9
+     */
+    public static <T, U, A, R>
+    Collector<T, ?, R> flatMapping(Function<? super T, ? extends Stream<? extends U>> mapper,
+                                   Collector<? super U, A, R> downstream) {
+        BiConsumer<A, ? super U> downstreamAccumulator = downstream.accumulator();
+        return new CollectorImpl<>(downstream.supplier(),
+                            (r, t) -> {
+                                try (Stream<? extends U> result = mapper.apply(t)) {
+                                    if (result != null)
+                                        result.sequential().forEach(u -> downstreamAccumulator.accept(r, u));
+                                }
+                            },
+                            downstream.combiner(), downstream.finisher(),
+                            downstream.characteristics());
+    }
+
+    /**
+     * Adapts a {@code Collector} to one accepting elements of the same type
+     * {@code T} by applying the predicate to each input element and only
+     * accumulating if the predicate returns {@code true}.
+     *
+     * @apiNote
+     * The {@code filtering()} collectors are most useful when used in a
+     * multi-level reduction, such as downstream of a {@code groupingBy} or
+     * {@code partitioningBy}.  For example, given a stream of
+     * {@code Employee}, to accumulate the employees in each department that have a
+     * salary above a certain threshold:
+     * <pre>{@code
+     * Map<Department, Set<Employee>> wellPaidEmployeesByDepartment
+     *   = employees.stream().collect(
+     *     groupingBy(Employee::getDepartment,
+     *                filtering(e -> e.getSalary() > 2000,
+     *                          toSet())));
+     * }</pre>
+     * A filtering collector differs from a stream's {@code filter()} operation.
+     * In this example, suppose there are no employees whose salary is above the
+     * threshold in some department.  Using a filtering collector as shown above
+     * would result in a mapping from that department to an empty {@code Set}.
+     * If a stream {@code filter()} operation were done instead, there would be
+     * no mapping for that department at all.
+     *
+     * @param <T> the type of the input elements
+     * @param <A> intermediate accumulation type of the downstream collector
+     * @param <R> result type of collector
+     * @param predicate a predicate to be applied to the input elements
+     * @param downstream a collector which will accept values that match the
+     * predicate
+     * @return a collector which applies the predicate to the input elements
+     * and provides matching elements to the downstream collector
+     * @since 9
+     */
+    public static <T, A, R>
+    Collector<T, ?, R> filtering(Predicate<? super T> predicate,
+                                 Collector<? super T, A, R> downstream) {
+        BiConsumer<A, ? super T> downstreamAccumulator = downstream.accumulator();
+        return new CollectorImpl<>(downstream.supplier(),
+                                   (r, t) -> {
+                                       if (predicate.test(t)) {
+                                           downstreamAccumulator.accept(r, t);
+                                       }
+                                   },
+                                   downstream.combiner(), downstream.finisher(),
+                                   downstream.characteristics());
+    }
+
+    /**
      * Adapts a {@code Collector} to perform an additional finishing
      * transformation.  For example, one could adapt the {@link #toList()}
      * collector to always produce an immutable list with:
      * <pre>{@code
-     *     List<String> people
-     *         = people.stream().collect(collectingAndThen(toList(), Collections::unmodifiableList));
+     * List<String> list = people.stream().collect(
+     *   collectingAndThen(toList(),
+     *                     Collections::unmodifiableList));
      * }</pre>
      *
      * @param <T> the type of the input elements
@@ -410,7 +616,7 @@
      */
     public static <T> Collector<T, ?, Long>
     counting() {
-        return reducing(0L, e -> 1L, Long::sum);
+        return summingLong(e -> 1L);
     }
 
     /**
@@ -515,8 +721,9 @@
          */
         return new CollectorImpl<>(
                 () -> new double[3],
-                (a, t) -> { sumWithCompensation(a, mapper.applyAsDouble(t));
-                            a[2] += mapper.applyAsDouble(t);},
+                (a, t) -> { double val = mapper.applyAsDouble(t);
+                            sumWithCompensation(a, val);
+                            a[2] += val;},
                 (a, b) -> { sumWithCompensation(a, b[0]);
                             a[2] += b[2];
                             return sumWithCompensation(a, b[1]); },
@@ -565,8 +772,9 @@
      * the result is 0.
      *
      * @param <T> the type of the input elements
-     * @param mapper a function extracting the property to be summed
-     * @return a {@code Collector} that produces the sum of a derived property
+     * @param mapper a function extracting the property to be averaged
+     * @return a {@code Collector} that produces the arithmetic mean of a
+     * derived property
      */
     public static <T> Collector<T, ?, Double>
     averagingInt(ToIntFunction<? super T> mapper) {
@@ -583,8 +791,9 @@
      * the result is 0.
      *
      * @param <T> the type of the input elements
-     * @param mapper a function extracting the property to be summed
-     * @return a {@code Collector} that produces the sum of a derived property
+     * @param mapper a function extracting the property to be averaged
+     * @return a {@code Collector} that produces the arithmetic mean of a
+     * derived property
      */
     public static <T> Collector<T, ?, Double>
     averagingLong(ToLongFunction<? super T> mapper) {
@@ -614,8 +823,9 @@
      * 2<sup>53</sup>, leading to additional numerical errors.
      *
      * @param <T> the type of the input elements
-     * @param mapper a function extracting the property to be summed
-     * @return a {@code Collector} that produces the sum of a derived property
+     * @param mapper a function extracting the property to be averaged
+     * @return a {@code Collector} that produces the arithmetic mean of a
+     * derived property
      */
     public static <T> Collector<T, ?, Double>
     averagingDouble(ToDoubleFunction<? super T> mapper) {
@@ -627,7 +837,7 @@
          */
         return new CollectorImpl<>(
                 () -> new double[4],
-                (a, t) -> { sumWithCompensation(a, mapper.applyAsDouble(t)); a[2]++; a[3]+= mapper.applyAsDouble(t);},
+                (a, t) -> { double val = mapper.applyAsDouble(t); sumWithCompensation(a, val); a[2]++; a[3]+= val;},
                 (a, b) -> { sumWithCompensation(a, b[0]); sumWithCompensation(a, b[1]); a[2] += b[2]; a[3] += b[3]; return a; },
                 a -> (a[2] == 0) ? 0.0d : (computeFinalSum(a) / a[2]),
                 CH_NOID);
@@ -682,9 +892,11 @@
      * <p>For example, given a stream of {@code Person}, to calculate tallest
      * person in each city:
      * <pre>{@code
-     *     Comparator<Person> byHeight = Comparator.comparing(Person::getHeight);
-     *     Map<City, Person> tallestByCity
-     *         = people.stream().collect(groupingBy(Person::getCity, reducing(BinaryOperator.maxBy(byHeight))));
+     * Comparator<Person> byHeight = Comparator.comparing(Person::getHeight);
+     * Map<City, Optional<Person>> tallestByCity
+     *   = people.stream().collect(
+     *     groupingBy(Person::getCity,
+     *                reducing(BinaryOperator.maxBy(byHeight))));
      * }</pre>
      *
      * @param <T> element type for the input and output of the reduction
@@ -735,10 +947,13 @@
      * <p>For example, given a stream of {@code Person}, to calculate the longest
      * last name of residents in each city:
      * <pre>{@code
-     *     Comparator<String> byLength = Comparator.comparing(String::length);
-     *     Map<City, String> longestLastNameByCity
-     *         = people.stream().collect(groupingBy(Person::getCity,
-     *                                              reducing(Person::getLastName, BinaryOperator.maxBy(byLength))));
+     * Comparator<String> byLength = Comparator.comparing(String::length);
+     * Map<City, String> longestLastNameByCity
+     *   = people.stream().collect(
+     *     groupingBy(Person::getCity,
+     *                reducing("",
+     *                         Person::getLastName,
+     *                         BinaryOperator.maxBy(byLength))));
      * }</pre>
      *
      * @param <T> the type of the input elements
@@ -822,9 +1037,11 @@
      *
      * <p>For example, to compute the set of last names of people in each city:
      * <pre>{@code
-     *     Map<City, Set<String>> namesByCity
-     *         = people.stream().collect(groupingBy(Person::getCity,
-     *                                              mapping(Person::getLastName, toSet())));
+     * Map<City, Set<String>> namesByCity
+     *   = people.stream().collect(
+     *     groupingBy(Person::getCity,
+     *                mapping(Person::getLastName,
+     *                        toSet())));
      * }</pre>
      *
      * @implNote
@@ -869,9 +1086,12 @@
      * <p>For example, to compute the set of last names of people in each city,
      * where the city names are sorted:
      * <pre>{@code
-     *     Map<City, Set<String>> namesByCity
-     *         = people.stream().collect(groupingBy(Person::getCity, TreeMap::new,
-     *                                              mapping(Person::getLastName, toSet())));
+     * Map<City, Set<String>> namesByCity
+     *   = people.stream().collect(
+     *     groupingBy(Person::getCity,
+     *                TreeMap::new,
+     *                mapping(Person::getLastName,
+     *                        toSet())));
      * }</pre>
      *
      * @implNote
@@ -889,8 +1109,8 @@
      * @param <M> the type of the resulting {@code Map}
      * @param classifier a classifier function mapping input elements to keys
      * @param downstream a {@code Collector} implementing the downstream reduction
-     * @param mapFactory a function which, when called, produces a new empty
-     *                   {@code Map} of the desired type
+     * @param mapFactory a supplier providing a new empty {@code Map}
+     *                   into which the results will be inserted
      * @return a {@code Collector} implementing the cascaded group-by operation
      *
      * @see #groupingBy(Function, Collector)
@@ -944,7 +1164,7 @@
      * function.
      *
      * <p>There are no guarantees on the type, mutability, or serializability
-     * of the {@code Map} or {@code List} objects returned, or of the
+     * of the {@code ConcurrentMap} or {@code List} objects returned, or of the
      * thread-safety of the {@code List} objects returned.
      * @implSpec
      * This produces a result similar to:
@@ -980,14 +1200,19 @@
      * <p>The classification function maps elements to some key type {@code K}.
      * The downstream collector operates on elements of type {@code T} and
      * produces a result of type {@code D}. The resulting collector produces a
-     * {@code Map<K, D>}.
+     * {@code ConcurrentMap<K, D>}.
+     *
+     * <p>There are no guarantees on the type, mutability, or serializability
+     * of the {@code ConcurrentMap} returned.
      *
      * <p>For example, to compute the set of last names of people in each city,
      * where the city names are sorted:
      * <pre>{@code
-     *     ConcurrentMap<City, Set<String>> namesByCity
-     *         = people.stream().collect(groupingByConcurrent(Person::getCity,
-     *                                                        mapping(Person::getLastName, toSet())));
+     * ConcurrentMap<City, Set<String>> namesByCity
+     *   = people.stream().collect(
+     *     groupingByConcurrent(Person::getCity,
+     *                          mapping(Person::getLastName,
+     *                                  toSet())));
      * }</pre>
      *
      * @param <T> the type of the input elements
@@ -1022,17 +1247,19 @@
      * <p>The classification function maps elements to some key type {@code K}.
      * The downstream collector operates on elements of type {@code T} and
      * produces a result of type {@code D}. The resulting collector produces a
-     * {@code Map<K, D>}.
+     * {@code ConcurrentMap<K, D>}.
      *
      * <p>For example, to compute the set of last names of people in each city,
      * where the city names are sorted:
      * <pre>{@code
-     *     ConcurrentMap<City, Set<String>> namesByCity
-     *         = people.stream().collect(groupingBy(Person::getCity, ConcurrentSkipListMap::new,
-     *                                              mapping(Person::getLastName, toSet())));
+     * ConcurrentMap<City, Set<String>> namesByCity
+     *   = people.stream().collect(
+     *     groupingByConcurrent(Person::getCity,
+     *                          ConcurrentSkipListMap::new,
+     *                          mapping(Person::getLastName,
+     *                                  toSet())));
      * }</pre>
      *
-     *
      * @param <T> the type of the input elements
      * @param <K> the type of the keys
      * @param <A> the intermediate accumulation type of the downstream collector
@@ -1040,8 +1267,8 @@
      * @param <M> the type of the resulting {@code ConcurrentMap}
      * @param classifier a classifier function mapping input elements to keys
      * @param downstream a {@code Collector} implementing the downstream reduction
-     * @param mapFactory a function which, when called, produces a new empty
-     *                   {@code ConcurrentMap} of the desired type
+     * @param mapFactory a supplier providing a new empty {@code ConcurrentMap}
+     *                   into which the results will be inserted
      * @return a concurrent, unordered {@code Collector} implementing the cascaded group-by operation
      *
      * @see #groupingByConcurrent(Function)
@@ -1096,8 +1323,15 @@
      * to a {@code Predicate}, and organizes them into a
      * {@code Map<Boolean, List<T>>}.
      *
+     * The returned {@code Map} always contains mappings for both
+     * {@code false} and {@code true} keys.
      * There are no guarantees on the type, mutability,
-     * serializability, or thread-safety of the {@code Map} returned.
+     * serializability, or thread-safety of the {@code Map} or {@code List}
+     * returned.
+     *
+     * @apiNote
+     * If a partition has no elements, its value in the result Map will be
+     * an empty List.
      *
      * @param <T> the type of the input elements
      * @param predicate a predicate used for classifying input elements
@@ -1117,9 +1351,17 @@
      * {@code Map<Boolean, D>} whose values are the result of the downstream
      * reduction.
      *
-     * <p>There are no guarantees on the type, mutability,
+     * <p>
+     * The returned {@code Map} always contains mappings for both
+     * {@code false} and {@code true} keys.
+     * There are no guarantees on the type, mutability,
      * serializability, or thread-safety of the {@code Map} returned.
      *
+     * @apiNote
+     * If a partition has no elements, its value in the result Map will be
+     * obtained by calling the downstream collector's supplier function and then
+     * applying the finisher function.
+     *
      * @param <T> the type of the input elements
      * @param <A> the intermediate accumulation type of the downstream collector
      * @param <D> the result type of the downstream reduction
@@ -1160,12 +1402,15 @@
      * {@code Map} whose keys and values are the result of applying the provided
      * mapping functions to the input elements.
      *
-     * <p>If the mapped keys contains duplicates (according to
+     * <p>If the mapped keys contain duplicates (according to
      * {@link Object#equals(Object)}), an {@code IllegalStateException} is
      * thrown when the collection operation is performed.  If the mapped keys
-     * may have duplicates, use {@link #toMap(Function, Function, BinaryOperator)}
+     * might have duplicates, use {@link #toMap(Function, Function, BinaryOperator)}
      * instead.
      *
+     * <p>There are no guarantees on the type, mutability, serializability,
+     * or thread-safety of the {@code Map} returned.
+     *
      * @apiNote
      * It is common for either the key or the value to be the input elements.
      * In this case, the utility method
@@ -1173,16 +1418,18 @@
      * For example, the following produces a {@code Map} mapping
      * students to their grade point average:
      * <pre>{@code
-     *     Map<Student, Double> studentToGPA
-     *         students.stream().collect(toMap(Functions.identity(),
-     *                                         student -> computeGPA(student)));
+     * Map<Student, Double> studentToGPA
+     *   = students.stream().collect(
+     *     toMap(Function.identity(),
+     *           student -> computeGPA(student)));
      * }</pre>
      * And the following produces a {@code Map} mapping a unique identifier to
      * students:
      * <pre>{@code
-     *     Map<String, Student> studentIdToStudent
-     *         students.stream().collect(toMap(Student::getId,
-     *                                         Functions.identity());
+     * Map<String, Student> studentIdToStudent
+     *   = students.stream().collect(
+     *     toMap(Student::getId,
+     *           Function.identity()));
      * }</pre>
      *
      * @implNote
@@ -1209,7 +1456,49 @@
     public static <T, K, U>
     Collector<T, ?, Map<K,U>> toMap(Function<? super T, ? extends K> keyMapper,
                                     Function<? super T, ? extends U> valueMapper) {
-        return toMap(keyMapper, valueMapper, throwingMerger(), HashMap::new);
+        return new CollectorImpl<>(HashMap::new,
+                                   uniqKeysMapAccumulator(keyMapper, valueMapper),
+                                   uniqKeysMapMerger(),
+                                   CH_ID);
+    }
+
+    /**
+     * Returns a {@code Collector} that accumulates the input elements into an
+     * <a href="../Map.html#unmodifiable">unmodifiable Map</a>,
+     * whose keys and values are the result of applying the provided
+     * mapping functions to the input elements.
+     *
+     * <p>If the mapped keys contain duplicates (according to
+     * {@link Object#equals(Object)}), an {@code IllegalStateException} is
+     * thrown when the collection operation is performed.  If the mapped keys
+     * might have duplicates, use {@link #toUnmodifiableMap(Function, Function, BinaryOperator)}
+     * to handle merging of the values.
+     *
+     * <p>The returned Collector disallows null keys and values. If either mapping function
+     * returns null, {@code NullPointerException} will be thrown.
+     *
+     * @param <T> the type of the input elements
+     * @param <K> the output type of the key mapping function
+     * @param <U> the output type of the value mapping function
+     * @param keyMapper a mapping function to produce keys, must be non-null
+     * @param valueMapper a mapping function to produce values, must be non-null
+     * @return a {@code Collector} that accumulates the input elements into an
+     * <a href="../Map.html#unmodifiable">unmodifiable Map</a>, whose keys and values
+     * are the result of applying the provided mapping functions to the input elements
+     * @throws NullPointerException if either keyMapper or valueMapper is null
+     *
+     * @see #toUnmodifiableMap(Function, Function, BinaryOperator)
+     * @since 10
+     */
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public static <T, K, U>
+    Collector<T, ?, Map<K,U>> toUnmodifiableMap(Function<? super T, ? extends K> keyMapper,
+                                                Function<? super T, ? extends U> valueMapper) {
+        Objects.requireNonNull(keyMapper, "keyMapper");
+        Objects.requireNonNull(valueMapper, "valueMapper");
+        return collectingAndThen(
+                toMap(keyMapper, valueMapper),
+                map -> (Map<K,U>)Map.ofEntries(map.entrySet().toArray(new Map.Entry[0])));
     }
 
     /**
@@ -1218,10 +1507,13 @@
      * mapping functions to the input elements.
      *
      * <p>If the mapped
-     * keys contains duplicates (according to {@link Object#equals(Object)}),
+     * keys contain duplicates (according to {@link Object#equals(Object)}),
      * the value mapping function is applied to each equal element, and the
      * results are merged using the provided merging function.
      *
+     * <p>There are no guarantees on the type, mutability, serializability,
+     * or thread-safety of the {@code Map} returned.
+     *
      * @apiNote
      * There are multiple ways to deal with collisions between multiple elements
      * mapping to the same key.  The other forms of {@code toMap} simply use
@@ -1229,13 +1521,14 @@
      * more flexible merge policies.  For example, if you have a stream
      * of {@code Person}, and you want to produce a "phone book" mapping name to
      * address, but it is possible that two persons have the same name, you can
-     * do as follows to gracefully deals with these collisions, and produce a
+     * do as follows to gracefully deal with these collisions, and produce a
      * {@code Map} mapping names to a concatenated list of addresses:
      * <pre>{@code
-     *     Map<String, String> phoneBook
-     *         people.stream().collect(toMap(Person::getName,
-     *                                       Person::getAddress,
-     *                                       (s, a) -> s + ", " + a));
+     * Map<String, String> phoneBook
+     *   = people.stream().collect(
+     *     toMap(Person::getName,
+     *           Person::getAddress,
+     *           (s, a) -> s + ", " + a));
      * }</pre>
      *
      * @implNote
@@ -1271,13 +1564,58 @@
         return toMap(keyMapper, valueMapper, mergeFunction, HashMap::new);
     }
 
+
+    /**
+     * Returns a {@code Collector} that accumulates the input elements into an
+     * <a href="../Map.html#unmodifiable">unmodifiable Map</a>,
+     * whose keys and values are the result of applying the provided
+     * mapping functions to the input elements.
+     *
+     * <p>If the mapped
+     * keys contain duplicates (according to {@link Object#equals(Object)}),
+     * the value mapping function is applied to each equal element, and the
+     * results are merged using the provided merging function.
+     *
+     * <p>The returned Collector disallows null keys and values. If either mapping function
+     * returns null, {@code NullPointerException} will be thrown.
+     *
+     * @param <T> the type of the input elements
+     * @param <K> the output type of the key mapping function
+     * @param <U> the output type of the value mapping function
+     * @param keyMapper a mapping function to produce keys, must be non-null
+     * @param valueMapper a mapping function to produce values, must be non-null
+     * @param mergeFunction a merge function, used to resolve collisions between
+     *                      values associated with the same key, as supplied
+     *                      to {@link Map#merge(Object, Object, BiFunction)},
+     *                      must be non-null
+     * @return a {@code Collector} that accumulates the input elements into an
+     * <a href="../Map.html#unmodifiable">unmodifiable Map</a>, whose keys and values
+     * are the result of applying the provided mapping functions to the input elements
+     * @throws NullPointerException if the keyMapper, valueMapper, or mergeFunction is null
+     *
+     * @see #toUnmodifiableMap(Function, Function)
+     * @since 10
+     */
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public static <T, K, U>
+    Collector<T, ?, Map<K,U>> toUnmodifiableMap(Function<? super T, ? extends K> keyMapper,
+                                                Function<? super T, ? extends U> valueMapper,
+                                                BinaryOperator<U> mergeFunction) {
+        Objects.requireNonNull(keyMapper, "keyMapper");
+        Objects.requireNonNull(valueMapper, "valueMapper");
+        Objects.requireNonNull(mergeFunction, "mergeFunction");
+        return collectingAndThen(
+                toMap(keyMapper, valueMapper, mergeFunction, HashMap::new),
+                map -> (Map<K,U>)Map.ofEntries(map.entrySet().toArray(new Map.Entry[0])));
+    }
+
     /**
      * Returns a {@code Collector} that accumulates elements into a
      * {@code Map} whose keys and values are the result of applying the provided
      * mapping functions to the input elements.
      *
      * <p>If the mapped
-     * keys contains duplicates (according to {@link Object#equals(Object)}),
+     * keys contain duplicates (according to {@link Object#equals(Object)}),
      * the value mapping function is applied to each equal element, and the
      * results are merged using the provided merging function.  The {@code Map}
      * is created by a provided supplier function.
@@ -1299,8 +1637,8 @@
      * @param mergeFunction a merge function, used to resolve collisions between
      *                      values associated with the same key, as supplied
      *                      to {@link Map#merge(Object, Object, BiFunction)}
-     * @param mapSupplier a function which returns a new, empty {@code Map} into
-     *                    which the results will be inserted
+     * @param mapFactory a supplier providing a new empty {@code Map}
+     *                   into which the results will be inserted
      * @return a {@code Collector} which collects elements into a {@code Map}
      * whose keys are the result of applying a key mapping function to the input
      * elements, and whose values are the result of applying a value mapping
@@ -1313,13 +1651,13 @@
      */
     public static <T, K, U, M extends Map<K, U>>
     Collector<T, ?, M> toMap(Function<? super T, ? extends K> keyMapper,
-                                Function<? super T, ? extends U> valueMapper,
-                                BinaryOperator<U> mergeFunction,
-                                Supplier<M> mapSupplier) {
+                             Function<? super T, ? extends U> valueMapper,
+                             BinaryOperator<U> mergeFunction,
+                             Supplier<M> mapFactory) {
         BiConsumer<M, T> accumulator
                 = (map, element) -> map.merge(keyMapper.apply(element),
                                               valueMapper.apply(element), mergeFunction);
-        return new CollectorImpl<>(mapSupplier, accumulator, mapMerger(mergeFunction), CH_ID);
+        return new CollectorImpl<>(mapFactory, accumulator, mapMerger(mergeFunction), CH_ID);
     }
 
     /**
@@ -1327,29 +1665,34 @@
      * {@code ConcurrentMap} whose keys and values are the result of applying
      * the provided mapping functions to the input elements.
      *
-     * <p>If the mapped keys contains duplicates (according to
+     * <p>If the mapped keys contain duplicates (according to
      * {@link Object#equals(Object)}), an {@code IllegalStateException} is
      * thrown when the collection operation is performed.  If the mapped keys
      * may have duplicates, use
      * {@link #toConcurrentMap(Function, Function, BinaryOperator)} instead.
      *
+     * <p>There are no guarantees on the type, mutability, or serializability
+     * of the {@code ConcurrentMap} returned.
+     *
      * @apiNote
      * It is common for either the key or the value to be the input elements.
      * In this case, the utility method
      * {@link java.util.function.Function#identity()} may be helpful.
-     * For example, the following produces a {@code Map} mapping
+     * For example, the following produces a {@code ConcurrentMap} mapping
      * students to their grade point average:
      * <pre>{@code
-     *     Map<Student, Double> studentToGPA
-     *         students.stream().collect(toMap(Functions.identity(),
-     *                                         student -> computeGPA(student)));
+     * ConcurrentMap<Student, Double> studentToGPA
+     *   = students.stream().collect(
+     *     toConcurrentMap(Function.identity(),
+     *                     student -> computeGPA(student)));
      * }</pre>
-     * And the following produces a {@code Map} mapping a unique identifier to
-     * students:
+     * And the following produces a {@code ConcurrentMap} mapping a
+     * unique identifier to students:
      * <pre>{@code
-     *     Map<String, Student> studentIdToStudent
-     *         students.stream().collect(toConcurrentMap(Student::getId,
-     *                                                   Functions.identity());
+     * ConcurrentMap<String, Student> studentIdToStudent
+     *   = students.stream().collect(
+     *     toConcurrentMap(Student::getId,
+     *                     Function.identity()));
      * }</pre>
      *
      * <p>This is a {@link Collector.Characteristics#CONCURRENT concurrent} and
@@ -1372,7 +1715,10 @@
     public static <T, K, U>
     Collector<T, ?, ConcurrentMap<K,U>> toConcurrentMap(Function<? super T, ? extends K> keyMapper,
                                                         Function<? super T, ? extends U> valueMapper) {
-        return toConcurrentMap(keyMapper, valueMapper, throwingMerger(), ConcurrentHashMap::new);
+        return new CollectorImpl<>(ConcurrentHashMap::new,
+                                   uniqKeysMapAccumulator(keyMapper, valueMapper),
+                                   uniqKeysMapMerger(),
+                                   CH_CONCURRENT_ID);
     }
 
     /**
@@ -1380,10 +1726,13 @@
      * {@code ConcurrentMap} whose keys and values are the result of applying
      * the provided mapping functions to the input elements.
      *
-     * <p>If the mapped keys contains duplicates (according to {@link Object#equals(Object)}),
+     * <p>If the mapped keys contain duplicates (according to {@link Object#equals(Object)}),
      * the value mapping function is applied to each equal element, and the
      * results are merged using the provided merging function.
      *
+     * <p>There are no guarantees on the type, mutability, or serializability
+     * of the {@code ConcurrentMap} returned.
+     *
      * @apiNote
      * There are multiple ways to deal with collisions between multiple elements
      * mapping to the same key.  The other forms of {@code toConcurrentMap} simply use
@@ -1391,13 +1740,14 @@
      * more flexible merge policies.  For example, if you have a stream
      * of {@code Person}, and you want to produce a "phone book" mapping name to
      * address, but it is possible that two persons have the same name, you can
-     * do as follows to gracefully deals with these collisions, and produce a
-     * {@code Map} mapping names to a concatenated list of addresses:
+     * do as follows to gracefully deal with these collisions, and produce a
+     * {@code ConcurrentMap} mapping names to a concatenated list of addresses:
      * <pre>{@code
-     *     Map<String, String> phoneBook
-     *         people.stream().collect(toConcurrentMap(Person::getName,
-     *                                                 Person::getAddress,
-     *                                                 (s, a) -> s + ", " + a));
+     * ConcurrentMap<String, String> phoneBook
+     *   = people.stream().collect(
+     *     toConcurrentMap(Person::getName,
+     *                     Person::getAddress,
+     *                     (s, a) -> s + ", " + a));
      * }</pre>
      *
      * <p>This is a {@link Collector.Characteristics#CONCURRENT concurrent} and
@@ -1434,7 +1784,7 @@
      * {@code ConcurrentMap} whose keys and values are the result of applying
      * the provided mapping functions to the input elements.
      *
-     * <p>If the mapped keys contains duplicates (according to {@link Object#equals(Object)}),
+     * <p>If the mapped keys contain duplicates (according to {@link Object#equals(Object)}),
      * the value mapping function is applied to each equal element, and the
      * results are merged using the provided merging function.  The
      * {@code ConcurrentMap} is created by a provided supplier function.
@@ -1451,8 +1801,8 @@
      * @param mergeFunction a merge function, used to resolve collisions between
      *                      values associated with the same key, as supplied
      *                      to {@link Map#merge(Object, Object, BiFunction)}
-     * @param mapSupplier a function which returns a new, empty {@code Map} into
-     *                    which the results will be inserted
+     * @param mapFactory a supplier providing a new empty {@code ConcurrentMap}
+     *                   into which the results will be inserted
      * @return a concurrent, unordered {@code Collector} which collects elements into a
      * {@code ConcurrentMap} whose keys are the result of applying a key mapping
      * function to the input elements, and whose values are the result of
@@ -1467,11 +1817,11 @@
     Collector<T, ?, M> toConcurrentMap(Function<? super T, ? extends K> keyMapper,
                                        Function<? super T, ? extends U> valueMapper,
                                        BinaryOperator<U> mergeFunction,
-                                       Supplier<M> mapSupplier) {
+                                       Supplier<M> mapFactory) {
         BiConsumer<M, T> accumulator
                 = (map, element) -> map.merge(keyMapper.apply(element),
                                               valueMapper.apply(element), mergeFunction);
-        return new CollectorImpl<>(mapSupplier, accumulator, mapMerger(mergeFunction), CH_CONCURRENT_ID);
+        return new CollectorImpl<>(mapFactory, accumulator, mapMerger(mergeFunction), CH_CONCURRENT_ID);
     }
 
     /**
@@ -1550,12 +1900,12 @@
 
         @Override
         public Set<Map.Entry<Boolean, T>> entrySet() {
-            return new AbstractSet<Map.Entry<Boolean, T>>() {
+            return new AbstractSet<>() {
                 @Override
                 public Iterator<Map.Entry<Boolean, T>> iterator() {
                     Map.Entry<Boolean, T> falseEntry = new SimpleImmutableEntry<>(false, forFalse);
                     Map.Entry<Boolean, T> trueEntry = new SimpleImmutableEntry<>(true, forTrue);
-                    return Arrays.asList(falseEntry, trueEntry).iterator();
+                    return List.of(falseEntry, trueEntry).iterator();
                 }
 
                 @Override
diff --git a/ojluni/src/main/java/jdk/net/ExtendedSocketOptions.java b/ojluni/src/main/java/jdk/net/ExtendedSocketOptions.java
index 644fc4d..74a7bc8 100644
--- a/ojluni/src/main/java/jdk/net/ExtendedSocketOptions.java
+++ b/ojluni/src/main/java/jdk/net/ExtendedSocketOptions.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,12 +25,23 @@
 
 package jdk.net;
 
+import java.io.FileDescriptor;
+import java.net.SocketException;
 import java.net.SocketOption;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import jdk.internal.misc.JavaIOFileDescriptorAccess;
+import jdk.internal.misc.SharedSecrets;
 
 /**
  * Defines extended socket options, beyond those defined in
  * {@link java.net.StandardSocketOptions}. These options may be platform
  * specific.
+ *
+ * @since 1.8
  */
 // Android-removed: @jdk.Exported, not present on Android.
 // @jdk.Exported
@@ -48,7 +59,7 @@
         @Override public String toString() { return name; }
     }
 
-    private ExtendedSocketOptions() {}
+    private ExtendedSocketOptions() { }
 
     /**
      * Service level properties. When a security manager is installed,
@@ -58,4 +69,347 @@
      */
     public static final SocketOption<SocketFlow> SO_FLOW_SLA = new
         ExtSocketOption<SocketFlow>("SO_FLOW_SLA", SocketFlow.class);
+
+    /**
+     * Disable Delayed Acknowledgements.
+     *
+     * <p>
+     * This socket option can be used to reduce or disable delayed
+     * acknowledgments (ACKs). When {@code TCP_QUICKACK} is enabled, ACKs are
+     * sent immediately, rather than delayed if needed in accordance to normal
+     * TCP operation. This option is not permanent, it only enables a switch to
+     * or from {@code TCP_QUICKACK} mode. Subsequent operations of the TCP
+     * protocol will once again disable/enable {@code TCP_QUICKACK} mode
+     * depending on internal protocol processing and factors such as delayed ACK
+     * timeouts occurring and data transfer, therefore this option needs to be
+     * set with {@code setOption} after each operation of TCP on a given socket.
+     *
+     * <p>
+     * The value of this socket option is a {@code Boolean} that represents
+     * whether the option is enabled or disabled. The socket option is specific
+     * to stream-oriented sockets using the TCP/IP protocol. The exact semantics
+     * of this socket option are socket type and system dependent.
+     *
+     * @since 10
+     */
+    public static final SocketOption<Boolean> TCP_QUICKACK =
+            new ExtSocketOption<Boolean>("TCP_QUICKACK", Boolean.class);
+
+    /**
+     * Keep-Alive idle time.
+     *
+     * <p>
+     * The value of this socket option is an {@code Integer} that is the number
+     * of seconds of idle time before keep-alive initiates a probe. The socket
+     * option is specific to stream-oriented sockets using the TCP/IP protocol.
+     * The exact semantics of this socket option are system dependent.
+     *
+     * <p>
+     * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE
+     * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been
+     * idle for some amount of time. The default value for this idle period is
+     * system dependent, but is typically 2 hours. The {@code TCP_KEEPIDLE}
+     * option can be used to affect this value for a given socket.
+     *
+     * @since 11
+     */
+    public static final SocketOption<Integer> TCP_KEEPIDLE
+            = new ExtSocketOption<Integer>("TCP_KEEPIDLE", Integer.class);
+
+    /**
+     * Keep-Alive retransmission interval time.
+     *
+     * <p>
+     * The value of this socket option is an {@code Integer} that is the number
+     * of seconds to wait before retransmitting a keep-alive probe. The socket
+     * option is specific to stream-oriented sockets using the TCP/IP protocol.
+     * The exact semantics of this socket option are system dependent.
+     *
+     * <p>
+     * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE
+     * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been
+     * idle for some amount of time. If the remote system does not respond to a
+     * keep-alive probe, TCP retransmits the probe after some amount of time.
+     * The default value for this retransmission interval is system dependent,
+     * but is typically 75 seconds. The {@code TCP_KEEPINTERVAL} option can be
+     * used to affect this value for a given socket.
+     *
+     * @since 11
+     */
+    public static final SocketOption<Integer> TCP_KEEPINTERVAL
+            = new ExtSocketOption<Integer>("TCP_KEEPINTERVAL", Integer.class);
+
+    /**
+     * Keep-Alive retransmission maximum limit.
+     *
+     * <p>
+     * The value of this socket option is an {@code Integer} that is the maximum
+     * number of keep-alive probes to be sent. The socket option is specific to
+     * stream-oriented sockets using the TCP/IP protocol. The exact semantics of
+     * this socket option are system dependent.
+     *
+     * <p>
+     * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE
+     * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been
+     * idle for some amount of time. If the remote system does not respond to a
+     * keep-alive probe, TCP retransmits the probe a certain number of times
+     * before a connection is considered to be broken. The default value for
+     * this keep-alive probe retransmit limit is system dependent, but is
+     * typically 8. The {@code TCP_KEEPCOUNT} option can be used to affect this
+     * value for a given socket.
+     *
+     * @since 11
+     */
+    public static final SocketOption<Integer> TCP_KEEPCOUNT
+            = new ExtSocketOption<Integer>("TCP_KEEPCOUNT", Integer.class);
+
+    private static final PlatformSocketOptions platformSocketOptions =
+            PlatformSocketOptions.get();
+
+    private static final boolean flowSupported =
+            platformSocketOptions.flowSupported();
+    private static final boolean quickAckSupported =
+            platformSocketOptions.quickAckSupported();
+    private static final boolean keepAliveOptSupported =
+            platformSocketOptions.keepAliveOptionsSupported();
+    private static final Set<SocketOption<?>> extendedOptions = options();
+
+    static Set<SocketOption<?>> options() {
+        Set<SocketOption<?>> options = new HashSet<>();
+        if (flowSupported) {
+            options.add(SO_FLOW_SLA);
+        }
+        if (quickAckSupported) {
+            options.add(TCP_QUICKACK);
+        }
+        if (keepAliveOptSupported) {
+            options.addAll(Set.of(TCP_KEEPCOUNT, TCP_KEEPIDLE, TCP_KEEPINTERVAL));
+        }
+        return Collections.unmodifiableSet(options);
+    }
+
+    static {
+        // Registers the extended socket options with the base module.
+        sun.net.ext.ExtendedSocketOptions.register(
+                new sun.net.ext.ExtendedSocketOptions(extendedOptions) {
+
+            @Override
+            public void setOption(FileDescriptor fd,
+                                  SocketOption<?> option,
+                                  Object value)
+                throws SocketException
+            {
+                SecurityManager sm = System.getSecurityManager();
+                if (sm != null)
+                    sm.checkPermission(new NetworkPermission("setOption." + option.name()));
+
+                if (fd == null || !fd.valid())
+                    throw new SocketException("socket closed");
+
+                if (option == SO_FLOW_SLA) {
+                    assert flowSupported;
+                    SocketFlow flow = checkValueType(value, option.type());
+                    setFlowOption(fd, flow);
+                } else if (option == TCP_QUICKACK) {
+                    setQuickAckOption(fd, (boolean) value);
+                } else if (option == TCP_KEEPCOUNT) {
+                    setTcpkeepAliveProbes(fd, (Integer) value);
+                } else if (option == TCP_KEEPIDLE) {
+                    setTcpKeepAliveTime(fd, (Integer) value);
+                } else if (option == TCP_KEEPINTERVAL) {
+                    setTcpKeepAliveIntvl(fd, (Integer) value);
+                } else {
+                    throw new InternalError("Unexpected option " + option);
+                }
+            }
+
+            @Override
+            public Object getOption(FileDescriptor fd,
+                                    SocketOption<?> option)
+                throws SocketException
+            {
+                SecurityManager sm = System.getSecurityManager();
+                if (sm != null)
+                    sm.checkPermission(new NetworkPermission("getOption." + option.name()));
+
+                if (fd == null || !fd.valid())
+                    throw new SocketException("socket closed");
+
+                if (option == SO_FLOW_SLA) {
+                    assert flowSupported;
+                    SocketFlow flow = SocketFlow.create();
+                    getFlowOption(fd, flow);
+                    return flow;
+                } else if (option == TCP_QUICKACK) {
+                    return getQuickAckOption(fd);
+                } else if (option == TCP_KEEPCOUNT) {
+                    return getTcpkeepAliveProbes(fd);
+                } else if (option == TCP_KEEPIDLE) {
+                    return getTcpKeepAliveTime(fd);
+                } else if (option == TCP_KEEPINTERVAL) {
+                    return getTcpKeepAliveIntvl(fd);
+                } else {
+                    throw new InternalError("Unexpected option " + option);
+                }
+            }
+        });
+    }
+
+    @SuppressWarnings("unchecked")
+    private static <T> T checkValueType(Object value, Class<?> type) {
+        if (!type.isAssignableFrom(value.getClass())) {
+            String s = "Found: " + value.getClass() + ", Expected: " + type;
+            throw new IllegalArgumentException(s);
+        }
+        return (T) value;
+    }
+
+    private static final JavaIOFileDescriptorAccess fdAccess =
+            SharedSecrets.getJavaIOFileDescriptorAccess();
+
+    private static void setFlowOption(FileDescriptor fd, SocketFlow f)
+        throws SocketException
+    {
+        int status = platformSocketOptions.setFlowOption(fdAccess.get(fd),
+                                                         f.priority(),
+                                                         f.bandwidth());
+        f.status(status);  // augment the given flow with the status
+    }
+
+    private static void getFlowOption(FileDescriptor fd, SocketFlow f)
+            throws SocketException {
+        int status = platformSocketOptions.getFlowOption(fdAccess.get(fd), f);
+        f.status(status);  // augment the given flow with the status
+    }
+
+    private static void setQuickAckOption(FileDescriptor fd, boolean enable)
+            throws SocketException {
+        platformSocketOptions.setQuickAck(fdAccess.get(fd), enable);
+    }
+
+    private static Object getQuickAckOption(FileDescriptor fd)
+            throws SocketException {
+        return platformSocketOptions.getQuickAck(fdAccess.get(fd));
+    }
+
+    private static void setTcpkeepAliveProbes(FileDescriptor fd, int value)
+            throws SocketException {
+        platformSocketOptions.setTcpkeepAliveProbes(fdAccess.get(fd), value);
+    }
+
+    private static void setTcpKeepAliveTime(FileDescriptor fd, int value)
+            throws SocketException {
+        platformSocketOptions.setTcpKeepAliveTime(fdAccess.get(fd), value);
+    }
+
+    private static void setTcpKeepAliveIntvl(FileDescriptor fd, int value)
+            throws SocketException {
+        platformSocketOptions.setTcpKeepAliveIntvl(fdAccess.get(fd), value);
+    }
+
+    private static int getTcpkeepAliveProbes(FileDescriptor fd) throws SocketException {
+        return platformSocketOptions.getTcpkeepAliveProbes(fdAccess.get(fd));
+    }
+
+    private static int getTcpKeepAliveTime(FileDescriptor fd) throws SocketException {
+        return platformSocketOptions.getTcpKeepAliveTime(fdAccess.get(fd));
+    }
+
+    private static int getTcpKeepAliveIntvl(FileDescriptor fd) throws SocketException {
+        return platformSocketOptions.getTcpKeepAliveIntvl(fdAccess.get(fd));
+    }
+
+    static class PlatformSocketOptions {
+
+        protected PlatformSocketOptions() {}
+
+        @SuppressWarnings("unchecked")
+        private static PlatformSocketOptions newInstance(String cn) {
+            Class<PlatformSocketOptions> c;
+            try {
+                c = (Class<PlatformSocketOptions>)Class.forName(cn);
+                return c.getConstructor(new Class<?>[] { }).newInstance();
+            } catch (ReflectiveOperationException x) {
+                throw new AssertionError(x);
+            }
+        }
+
+        private static PlatformSocketOptions create() {
+            // Android-removed: other platforms are unsupported.
+//            String osname = AccessController.doPrivileged(
+//                    new PrivilegedAction<String>() {
+//                        public String run() {
+//                            return System.getProperty("os.name");
+//                        }
+//                    });
+//            if ("SunOS".equals(osname)) {
+//                return newInstance("jdk.net.SolarisSocketOptions");
+//            } else if ("Linux".equals(osname)) {
+//                return newInstance("jdk.net.LinuxSocketOptions");
+//            } else if (osname.startsWith("Mac")) {
+//                return newInstance("jdk.net.MacOSXSocketOptions");
+//            }
+            return new PlatformSocketOptions();
+        }
+
+        private static final PlatformSocketOptions instance = create();
+
+        static PlatformSocketOptions get() {
+            return instance;
+        }
+
+        int setFlowOption(int fd, int priority, long bandwidth)
+            throws SocketException
+        {
+            throw new UnsupportedOperationException("unsupported socket option");
+        }
+
+        int getFlowOption(int fd, SocketFlow f) throws SocketException {
+            throw new UnsupportedOperationException("unsupported socket option");
+        }
+
+        boolean flowSupported() {
+            return false;
+        }
+
+        void setQuickAck(int fd, boolean on) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_QUICKACK option");
+        }
+
+        boolean getQuickAck(int fd) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_QUICKACK option");
+        }
+
+        boolean quickAckSupported() {
+            return false;
+        }
+
+        boolean keepAliveOptionsSupported() {
+            return false;
+        }
+
+        void setTcpkeepAliveProbes(int fd, final int value) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_KEEPCNT option");
+        }
+
+        void setTcpKeepAliveTime(int fd, final int value) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_KEEPIDLE option");
+        }
+
+        void setTcpKeepAliveIntvl(int fd, final int value) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_KEEPINTVL option");
+        }
+
+        int getTcpkeepAliveProbes(int fd) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_KEEPCNT option");
+        }
+
+        int getTcpKeepAliveTime(int fd) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_KEEPIDLE option");
+        }
+
+        int getTcpKeepAliveIntvl(int fd) throws SocketException {
+            throw new UnsupportedOperationException("unsupported TCP_KEEPINTVL option");
+        }
+    }
 }
diff --git a/ojluni/src/main/java/jdk/net/SocketFlow.java b/ojluni/src/main/java/jdk/net/SocketFlow.java
index 59875a8..8777722 100644
--- a/ojluni/src/main/java/jdk/net/SocketFlow.java
+++ b/ojluni/src/main/java/jdk/net/SocketFlow.java
@@ -42,28 +42,33 @@
  * <p>
  * When a security manager is installed, a {@link NetworkPermission}
  * is required to set or get this option.
+ *
+ * @since 1.8
  */
 // Android-removed: @jdk.Exported, not present on Android.
 // @jdk.Exported
 public class SocketFlow {
 
-    private static final int UNSET = -1;
+    @Native public static final int UNSET = -1;
     @Native public static final int NORMAL_PRIORITY = 1;
     @Native public static final int HIGH_PRIORITY = 2;
 
-    private int priority = NORMAL_PRIORITY;
-
-    private long bandwidth = UNSET;
-
-    private Status status = Status.NO_STATUS;
-
-    private SocketFlow() {}
+    @Native private static final int NO_STATUS_VALUE = 0;
+    @Native private static final int OK_VALUE = 1;
+    @Native private static final int NO_PERMISSION_VALUE = 2;
+    @Native private static final int NOT_CONNECTED_VALUE = 3;
+    @Native private static final int NOT_SUPPORTED_VALUE = 4;
+    @Native private static final int ALREADY_CREATED_VALUE = 5;
+    @Native private static final int IN_PROGRESS_VALUE = 6;
+    @Native private static final int OTHER_VALUE = 7;
 
     /**
      * Enumeration of the return values from the SO_FLOW_SLA
      * socket option. Both setting and getting the option return
      * one of these statuses, which reflect the state of socket's
      * flow.
+     *
+     * @since 1.8
      */
     // Android-removed: @jdk.Exported, not present on Android.
     // @jdk.Exported
@@ -72,37 +77,56 @@
          * Set or get socket option has not been called yet. Status
          * values can only be retrieved after calling set or get.
          */
-        NO_STATUS,
+        NO_STATUS(NO_STATUS_VALUE),
         /**
          * Flow successfully created.
          */
-        OK,
+        OK(OK_VALUE),
         /**
          * Caller has no permission to create flow.
          */
-        NO_PERMISSION,
+        NO_PERMISSION(NO_PERMISSION_VALUE),
         /**
          * Flow can not be created because socket is not connected.
          */
-        NOT_CONNECTED,
+        NOT_CONNECTED(NOT_CONNECTED_VALUE),
         /**
          * Flow creation not supported for this socket.
          */
-        NOT_SUPPORTED,
+        NOT_SUPPORTED(NOT_SUPPORTED_VALUE),
         /**
          * A flow already exists with identical attributes.
          */
-        ALREADY_CREATED,
+        ALREADY_CREATED(ALREADY_CREATED_VALUE),
         /**
          * A flow is being created.
          */
-        IN_PROGRESS,
+        IN_PROGRESS(IN_PROGRESS_VALUE),
         /**
          * Some other unspecified error.
          */
-        OTHER
+        OTHER(OTHER_VALUE);
+
+        private final int value;
+        Status(int value) { this.value = value; }
+
+        static Status from(int value) {
+            if      (value == NO_STATUS.value)       return NO_STATUS;
+            else if (value == OK.value)              return OK;
+            else if (value == NO_PERMISSION.value)   return NO_PERMISSION;
+            else if (value == NOT_CONNECTED.value)   return NOT_CONNECTED;
+            else if (value == NOT_SUPPORTED.value)   return NOT_SUPPORTED;
+            else if (value == ALREADY_CREATED.value) return ALREADY_CREATED;
+            else if (value == IN_PROGRESS.value)     return IN_PROGRESS;
+            else if (value == OTHER.value)           return OTHER;
+            else     throw new InternalError("Unknown value: " + value);
+        }
     }
 
+    private int priority = NORMAL_PRIORITY;
+    private long bandwidth = UNSET;
+    private Status status = Status.NO_STATUS;
+
     /**
      * Creates a new SocketFlow that can be used to set the SO_FLOW_SLA
      * socket option and create a socket flow.
@@ -111,6 +135,8 @@
         return new SocketFlow();
     }
 
+    private SocketFlow() { }
+
     /**
      * Sets this SocketFlow's priority. Must be either NORMAL_PRIORITY
      * HIGH_PRIORITY. If not set, a flow's priority is normal.
@@ -119,9 +145,8 @@
      *         HIGH_PRIORITY.
      */
     public SocketFlow priority(int priority) {
-        if (priority != NORMAL_PRIORITY && priority != HIGH_PRIORITY) {
-            throw new IllegalArgumentException("invalid priority");
-        }
+        if (priority != NORMAL_PRIORITY && priority != HIGH_PRIORITY)
+            throw new IllegalArgumentException("invalid priority :" + priority);
         this.priority = priority;
         return this;
     }
@@ -133,11 +158,9 @@
      * @throws IllegalArgumentException if bandwidth is less than zero.
      */
     public SocketFlow bandwidth(long bandwidth) {
-        if (bandwidth < 0) {
-            throw new IllegalArgumentException("invalid bandwidth");
-        } else {
-            this.bandwidth = bandwidth;
-        }
+        if (bandwidth < 0)
+            throw new IllegalArgumentException("invalid bandwidth: " + bandwidth);
+        this.bandwidth = bandwidth;
         return this;
     }
 
@@ -164,4 +187,18 @@
     public Status status() {
         return status;
     }
+
+    void status(int status) {
+        this.status = Status.from(status);
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder(super.toString());
+        sb.append(" [ priority=").append(priority())
+          .append(", bandwidth=").append(bandwidth())
+          .append(", status=").append(status())
+          .append(" ]");
+        return sb.toString();
+    }
 }
diff --git a/ojluni/src/main/java/sun/net/ext/ExtendedSocketOptions.java b/ojluni/src/main/java/sun/net/ext/ExtendedSocketOptions.java
new file mode 100644
index 0000000..4036e11
--- /dev/null
+++ b/ojluni/src/main/java/sun/net/ext/ExtendedSocketOptions.java
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package sun.net.ext;
+
+import java.io.FileDescriptor;
+import java.net.SocketException;
+import java.net.SocketOption;
+import java.util.Collections;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * Defines the infrastructure to support extended socket options, beyond those
+ * defined in {@link java.net.StandardSocketOptions}.
+ *
+ * Extended socket options are accessed through the jdk.net API, which is in
+ * the jdk.net module.
+ */
+public abstract class ExtendedSocketOptions {
+
+    public static final short SOCK_STREAM = 1;
+    public static final short SOCK_DGRAM = 2;
+
+    private final Set<SocketOption<?>> options;
+
+    /** Tells whether or not the option is supported. */
+    public final boolean isOptionSupported(SocketOption<?> option) {
+        return options().contains(option);
+    }
+
+    /** Return the, possibly empty, set of extended socket options available. */
+    public final Set<SocketOption<?>> options() { return options; }
+
+    public static final Set<SocketOption<?>> options(short type) {
+        return getInstance().options0(type);
+    }
+
+    private Set<SocketOption<?>> options0(short type) {
+        Set<SocketOption<?>> extOptions = null;
+        switch (type) {
+            case SOCK_DGRAM:
+                extOptions = options.stream()
+                        .filter((option) -> !option.name().startsWith("TCP_"))
+                        .collect(Collectors.toUnmodifiableSet());
+                break;
+            case SOCK_STREAM:
+                extOptions = options.stream()
+                        .filter((option) -> !option.name().startsWith("UDP_"))
+                        .collect(Collectors.toUnmodifiableSet());
+                break;
+            default:
+                //this will never happen
+                throw new IllegalArgumentException("Invalid socket option type");
+        }
+        return extOptions;
+    }
+
+    /** Sets the value of a socket option, for the given socket. */
+    public abstract void setOption(FileDescriptor fd, SocketOption<?> option, Object value)
+            throws SocketException;
+
+    /** Returns the value of a socket option, for the given socket. */
+    public abstract Object getOption(FileDescriptor fd, SocketOption<?> option)
+            throws SocketException;
+
+    protected ExtendedSocketOptions(Set<SocketOption<?>> options) {
+        this.options = options;
+    }
+
+    private static volatile ExtendedSocketOptions instance;
+
+    public static final ExtendedSocketOptions getInstance() { return instance; }
+
+    /** Registers support for extended socket options. Invoked by the jdk.net module. */
+    public static final void register(ExtendedSocketOptions extOptions) {
+        if (instance != null)
+            throw new InternalError("Attempting to reregister extended options");
+
+        instance = extOptions;
+    }
+
+    static {
+        try {
+            // If the class is present, it will be initialized which
+            // triggers registration of the extended socket options.
+            Class<?> c = Class.forName("jdk.net.ExtendedSocketOptions");
+        } catch (ClassNotFoundException e) {
+            // the jdk.net module is not present => no extended socket options
+            instance = new NoExtendedSocketOptions();
+        }
+    }
+
+    static final class NoExtendedSocketOptions extends ExtendedSocketOptions {
+
+        NoExtendedSocketOptions() {
+            super(Collections.<SocketOption<?>>emptySet());
+        }
+
+        @Override
+        public void setOption(FileDescriptor fd, SocketOption<?> option, Object value)
+            throws SocketException
+        {
+            throw new UnsupportedOperationException(
+                    "no extended options: " + option.name());
+        }
+
+        @Override
+        public Object getOption(FileDescriptor fd, SocketOption<?> option)
+            throws SocketException
+        {
+            throw new UnsupportedOperationException(
+                    "no extended options: " + option.name());
+        }
+    }
+}
diff --git a/ojluni/src/test/java/util/stream/Collectors/CollectorsTest.java b/ojluni/src/test/java/util/stream/Collectors/CollectorsTest.java
new file mode 100644
index 0000000..20e47a2
--- /dev/null
+++ b/ojluni/src/test/java/util/stream/Collectors/CollectorsTest.java
@@ -0,0 +1,752 @@
+/*
+ * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package test.java.util.stream.Collectors;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.StringJoiner;
+import java.util.TreeMap;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentSkipListMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.testng.annotations.Test;
+import org.openjdk.testlib.java.util.stream.LambdaTestHelpers;
+import org.openjdk.testlib.java.util.stream.StreamOpFlagTestHelper;
+import org.openjdk.testlib.java.util.stream.StreamTestDataProvider;
+import org.openjdk.testlib.java.util.stream.TestData;
+import org.openjdk.testlib.java.util.stream.OpTestCase;
+
+import static java.util.stream.Collectors.collectingAndThen;
+import static java.util.stream.Collectors.flatMapping;
+import static java.util.stream.Collectors.filtering;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.groupingByConcurrent;
+import static java.util.stream.Collectors.mapping;
+import static java.util.stream.Collectors.partitioningBy;
+import static java.util.stream.Collectors.reducing;
+import static java.util.stream.Collectors.toCollection;
+import static java.util.stream.Collectors.toConcurrentMap;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toMap;
+import static java.util.stream.Collectors.toSet;
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertTrue;
+import static org.testng.Assert.fail;
+import static org.openjdk.testlib.java.util.stream.LambdaTestHelpers.assertContents;
+import static org.openjdk.testlib.java.util.stream.LambdaTestHelpers.assertContentsUnordered;
+import static org.openjdk.testlib.java.util.stream.LambdaTestHelpers.mDoubler;
+
+/*
+ * @test
+ * @bug 8071600 8144675
+ * @summary Test for collectors.
+ */
+public class CollectorsTest extends OpTestCase {
+
+    private abstract static class CollectorAssertion<T, U> {
+        abstract void assertValue(U value,
+                Supplier<Stream<T>> source,
+                boolean ordered) throws ReflectiveOperationException;
+    }
+
+    static class MappingAssertion<T, V, R> extends CollectorAssertion<T, R> {
+        private final Function<T, V> mapper;
+        private final CollectorAssertion<V, R> downstream;
+
+        MappingAssertion(Function<T, V> mapper, CollectorAssertion<V, R> downstream) {
+            this.mapper = mapper;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(R value, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
+            downstream.assertValue(value,
+                    () -> source.get().map(mapper::apply),
+                    ordered);
+        }
+    }
+
+    static class FlatMappingAssertion<T, V, R> extends CollectorAssertion<T, R> {
+        private final Function<T, Stream<V>> mapper;
+        private final CollectorAssertion<V, R> downstream;
+
+        FlatMappingAssertion(Function<T, Stream<V>> mapper,
+                CollectorAssertion<V, R> downstream) {
+            this.mapper = mapper;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(R value, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
+            downstream.assertValue(value,
+                    () -> source.get().flatMap(mapper::apply),
+                    ordered);
+        }
+    }
+
+    static class FilteringAssertion<T, R> extends CollectorAssertion<T, R> {
+        private final Predicate<T> filter;
+        private final CollectorAssertion<T, R> downstream;
+
+        public FilteringAssertion(Predicate<T> filter, CollectorAssertion<T, R> downstream) {
+            this.filter = filter;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(R value, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
+            downstream.assertValue(value,
+                    () -> source.get().filter(filter),
+                    ordered);
+        }
+    }
+
+    static class GroupingByAssertion<T, K, V, M extends Map<K, ? extends V>> extends CollectorAssertion<T, M> {
+        private final Class<? extends Map> clazz;
+        private final Function<T, K> classifier;
+        private final CollectorAssertion<T,V> downstream;
+
+        GroupingByAssertion(Function<T, K> classifier, Class<? extends Map> clazz,
+                CollectorAssertion<T, V> downstream) {
+            this.clazz = clazz;
+            this.classifier = classifier;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(M map,
+                Supplier<Stream<T>> source,
+                boolean ordered) throws ReflectiveOperationException {
+            if (!clazz.isAssignableFrom(map.getClass()))
+                fail(String.format("Class mismatch in GroupingByAssertion: %s, %s", clazz, map.getClass()));
+            assertContentsUnordered(map.keySet(), source.get().map(classifier).collect(toSet()));
+            for (Map.Entry<K, ? extends V> entry : map.entrySet()) {
+                K key = entry.getKey();
+                downstream.assertValue(entry.getValue(),
+                        () -> source.get().filter(e -> classifier.apply(e).equals(key)),
+                        ordered);
+            }
+        }
+    }
+
+    static class ToMapAssertion<T, K, V, M extends Map<K,V>> extends CollectorAssertion<T, M> {
+        private final Class<? extends Map> clazz;
+        private final Function<T, K> keyFn;
+        private final Function<T, V> valueFn;
+        private final BinaryOperator<V> mergeFn;
+
+        ToMapAssertion(Function<T, K> keyFn,
+                Function<T, V> valueFn,
+                BinaryOperator<V> mergeFn,
+                Class<? extends Map> clazz) {
+            this.clazz = clazz;
+            this.keyFn = keyFn;
+            this.valueFn = valueFn;
+            this.mergeFn = mergeFn;
+        }
+
+        @Override
+        void assertValue(M map, Supplier<Stream<T>> source, boolean ordered) throws ReflectiveOperationException {
+            if (!clazz.isAssignableFrom(map.getClass()))
+                fail(String.format("Class mismatch in ToMapAssertion: %s, %s", clazz, map.getClass()));
+            Set<K> uniqueKeys = source.get().map(keyFn).collect(toSet());
+            assertEquals(uniqueKeys, map.keySet());
+            source.get().forEach(t -> {
+                K key = keyFn.apply(t);
+                V v = source.get()
+                        .filter(e -> key.equals(keyFn.apply(e)))
+                        .map(valueFn)
+                        .reduce(mergeFn)
+                        .get();
+                assertEquals(map.get(key), v);
+            });
+        }
+    }
+
+    static class PartitioningByAssertion<T, D> extends CollectorAssertion<T, Map<Boolean,D>> {
+        private final Predicate<T> predicate;
+        private final CollectorAssertion<T,D> downstream;
+
+        PartitioningByAssertion(Predicate<T> predicate, CollectorAssertion<T, D> downstream) {
+            this.predicate = predicate;
+            this.downstream = downstream;
+        }
+
+        @Override
+        void assertValue(Map<Boolean, D> map,
+                Supplier<Stream<T>> source,
+                boolean ordered) throws ReflectiveOperationException {
+            if (!Map.class.isAssignableFrom(map.getClass()))
+                fail(String.format("Class mismatch in PartitioningByAssertion: %s", map.getClass()));
+            assertEquals(2, map.size());
+            downstream.assertValue(map.get(true), () -> source.get().filter(predicate), ordered);
+            downstream.assertValue(map.get(false), () -> source.get().filter(predicate.negate()), ordered);
+        }
+    }
+
+    static class ToListAssertion<T> extends CollectorAssertion<T, List<T>> {
+        @Override
+        void assertValue(List<T> value, Supplier<Stream<T>> source, boolean ordered)
+                throws ReflectiveOperationException {
+            if (!List.class.isAssignableFrom(value.getClass()))
+                fail(String.format("Class mismatch in ToListAssertion: %s", value.getClass()));
+            Stream<T> stream = source.get();
+            List<T> result = new ArrayList<>();
+            for (Iterator<T> it = stream.iterator(); it.hasNext(); ) // avoid capturing result::add
+                result.add(it.next());
+            if (StreamOpFlagTestHelper.isStreamOrdered(stream) && ordered)
+                assertContents(value, result);
+            else
+                assertContentsUnordered(value, result);
+        }
+    }
+
+    static class ToCollectionAssertion<T> extends CollectorAssertion<T, Collection<T>> {
+        private final Class<? extends Collection> clazz;
+        private final boolean targetOrdered;
+
+        ToCollectionAssertion(Class<? extends Collection> clazz, boolean targetOrdered) {
+            this.clazz = clazz;
+            this.targetOrdered = targetOrdered;
+        }
+
+        @Override
+        void assertValue(Collection<T> value, Supplier<Stream<T>> source, boolean ordered)
+                throws ReflectiveOperationException {
+            if (!clazz.isAssignableFrom(value.getClass()))
+                fail(String.format("Class mismatch in ToCollectionAssertion: %s, %s", clazz, value.getClass()));
+            Stream<T> stream = source.get();
+            Collection<T> result = clazz.newInstance();
+            for (Iterator<T> it = stream.iterator(); it.hasNext(); ) // avoid capturing result::add
+                result.add(it.next());
+            if (StreamOpFlagTestHelper.isStreamOrdered(stream) && targetOrdered && ordered)
+                assertContents(value, result);
+            else
+                assertContentsUnordered(value, result);
+        }
+    }
+
+    static class ReducingAssertion<T, U> extends CollectorAssertion<T, U> {
+        private final U identity;
+        private final Function<T, U> mapper;
+        private final BinaryOperator<U> reducer;
+
+        ReducingAssertion(U identity, Function<T, U> mapper, BinaryOperator<U> reducer) {
+            this.identity = identity;
+            this.mapper = mapper;
+            this.reducer = reducer;
+        }
+
+        @Override
+        void assertValue(U value, Supplier<Stream<T>> source, boolean ordered)
+                throws ReflectiveOperationException {
+            Optional<U> reduced = source.get().map(mapper).reduce(reducer);
+            if (value == null)
+                assertTrue(!reduced.isPresent());
+            else if (!reduced.isPresent()) {
+                assertEquals(value, identity);
+            }
+            else {
+                assertEquals(value, reduced.get());
+            }
+        }
+    }
+
+    private <T> ResultAsserter<T> mapTabulationAsserter(boolean ordered) {
+        return (act, exp, ord, par) -> {
+            if (par && (!ordered || !ord)) {
+                CollectorsTest.nestedMapEqualityAssertion(act, exp);
+            }
+            else {
+                LambdaTestHelpers.assertContentsEqual(act, exp);
+            }
+        };
+    }
+
+    private<T, M extends Map>
+    void exerciseMapCollection(TestData<T, Stream<T>> data,
+            Collector<T, ?, ? extends M> collector,
+            CollectorAssertion<T, M> assertion)
+            throws ReflectiveOperationException {
+        boolean ordered = !collector.characteristics().contains(Collector.Characteristics.UNORDERED);
+
+        M m = withData(data)
+                .terminal(s -> s.collect(collector))
+                .resultAsserter(mapTabulationAsserter(ordered))
+                .exercise();
+        assertion.assertValue(m, () -> data.stream(), ordered);
+
+        m = withData(data)
+                .terminal(s -> s.unordered().collect(collector))
+                .resultAsserter(mapTabulationAsserter(ordered))
+                .exercise();
+        assertion.assertValue(m, () -> data.stream(), false);
+    }
+
+    private static void nestedMapEqualityAssertion(Object o1, Object o2) {
+        if (o1 instanceof Map) {
+            Map m1 = (Map) o1;
+            Map m2 = (Map) o2;
+            assertContentsUnordered(m1.keySet(), m2.keySet());
+            for (Object k : m1.keySet())
+                nestedMapEqualityAssertion(m1.get(k), m2.get(k));
+        }
+        else if (o1 instanceof Collection) {
+            assertContentsUnordered(((Collection) o1), ((Collection) o2));
+        }
+        else
+            assertEquals(o1, o2);
+    }
+
+    private<T, R> void assertCollect(TestData.OfRef<T> data,
+            Collector<T, ?, R> collector,
+            Function<Stream<T>, R> streamReduction) {
+        R check = streamReduction.apply(data.stream());
+        withData(data).terminal(s -> s.collect(collector)).expectedResult(check).exercise();
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testReducing(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        assertCollect(data, Collectors.reducing(0, Integer::sum),
+                s -> s.reduce(0, Integer::sum));
+        assertCollect(data, Collectors.reducing(Integer.MAX_VALUE, Integer::min),
+                s -> s.min(Integer::compare).orElse(Integer.MAX_VALUE));
+        assertCollect(data, Collectors.reducing(Integer.MIN_VALUE, Integer::max),
+                s -> s.max(Integer::compare).orElse(Integer.MIN_VALUE));
+
+        assertCollect(data, Collectors.reducing(Integer::sum),
+                s -> s.reduce(Integer::sum));
+        assertCollect(data, Collectors.minBy(Comparator.naturalOrder()),
+                s -> s.min(Integer::compare));
+        assertCollect(data, Collectors.maxBy(Comparator.naturalOrder()),
+                s -> s.max(Integer::compare));
+
+        assertCollect(data, Collectors.reducing(0, x -> x*2, Integer::sum),
+                s -> s.map(x -> x*2).reduce(0, Integer::sum));
+
+        assertCollect(data, Collectors.summingLong(x -> x * 2L),
+                s -> s.map(x -> x*2L).reduce(0L, Long::sum));
+        assertCollect(data, Collectors.summingInt(x -> x * 2),
+                s -> s.map(x -> x*2).reduce(0, Integer::sum));
+        assertCollect(data, Collectors.summingDouble(x -> x * 2.0d),
+                s -> s.map(x -> x * 2.0d).reduce(0.0d, Double::sum));
+
+        assertCollect(data, Collectors.averagingInt(x -> x * 2),
+                s -> s.mapToInt(x -> x * 2).average().orElse(0));
+        assertCollect(data, Collectors.averagingLong(x -> x * 2),
+                s -> s.mapToLong(x -> x * 2).average().orElse(0));
+        assertCollect(data, Collectors.averagingDouble(x -> x * 2),
+                s -> s.mapToDouble(x -> x * 2).average().orElse(0));
+
+        // Test explicit Collector.of
+        Collector<Integer, long[], Double> avg2xint = Collector.of(() -> new long[2],
+                (a, b) -> {
+                    a[0] += b * 2;
+                    a[1]++;
+                },
+                (a, b) -> {
+                    a[0] += b[0];
+                    a[1] += b[1];
+                    return a;
+                },
+                a -> a[1] == 0 ? 0.0d : (double) a[0] / a[1]);
+        assertCollect(data, avg2xint,
+                s -> s.mapToInt(x -> x * 2).average().orElse(0));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testJoining(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(Collectors.joining()))
+                .expectedResult(join(data, ""))
+                .exercise();
+
+        Collector<String, StringBuilder, String> likeJoining = Collector.of(StringBuilder::new, StringBuilder::append, (sb1, sb2) -> sb1.append(sb2.toString()), StringBuilder::toString);
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(likeJoining))
+                .expectedResult(join(data, ""))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(Collectors.joining(",")))
+                .expectedResult(join(data, ","))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString).collect(Collectors.joining(",", "[", "]")))
+                .expectedResult("[" + join(data, ",") + "]")
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString)
+                        .collect(StringBuilder::new, StringBuilder::append, StringBuilder::append)
+                        .toString())
+                .expectedResult(join(data, ""))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString)
+                        .collect(() -> new StringJoiner(","),
+                                (sj, cs) -> sj.add(cs),
+                                (j1, j2) -> j1.merge(j2))
+                        .toString())
+                .expectedResult(join(data, ","))
+                .exercise();
+
+        withData(data)
+                .terminal(s -> s.map(Object::toString)
+                        .collect(() -> new StringJoiner(",", "[", "]"),
+                                (sj, cs) -> sj.add(cs),
+                                (j1, j2) -> j1.merge(j2))
+                        .toString())
+                .expectedResult("[" + join(data, ",") + "]")
+                .exercise();
+    }
+
+    private<T> String join(TestData.OfRef<T> data, String delim) {
+        StringBuilder sb = new StringBuilder();
+        boolean first = true;
+        for (T i : data) {
+            if (!first)
+                sb.append(delim);
+            sb.append(i.toString());
+            first = false;
+        }
+        return sb.toString();
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testSimpleToMap(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> keyFn = i -> i * 2;
+        Function<Integer, Integer> valueFn = i -> i * 4;
+
+        List<Integer> dataAsList = Arrays.asList(data.stream().toArray(Integer[]::new));
+        Set<Integer> dataAsSet = new HashSet<>(dataAsList);
+
+        BinaryOperator<Integer> sum = Integer::sum;
+        for (BinaryOperator<Integer> op : Arrays.asList((u, v) -> u,
+                (u, v) -> v,
+                sum)) {
+            try {
+                exerciseMapCollection(data, toMap(keyFn, valueFn),
+                        new ToMapAssertion<>(keyFn, valueFn, op, HashMap.class));
+                if (dataAsList.size() != dataAsSet.size())
+                    fail("Expected ISE on input with duplicates");
+            }
+            catch (IllegalStateException e) {
+                if (dataAsList.size() == dataAsSet.size())
+                    fail("Expected no ISE on input without duplicates");
+            }
+
+            exerciseMapCollection(data, toMap(keyFn, valueFn, op),
+                    new ToMapAssertion<>(keyFn, valueFn, op, HashMap.class));
+
+            exerciseMapCollection(data, toMap(keyFn, valueFn, op, TreeMap::new),
+                    new ToMapAssertion<>(keyFn, valueFn, op, TreeMap.class));
+        }
+
+        // For concurrent maps, only use commutative merge functions
+        try {
+            exerciseMapCollection(data, toConcurrentMap(keyFn, valueFn),
+                    new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentHashMap.class));
+            if (dataAsList.size() != dataAsSet.size())
+                fail("Expected ISE on input with duplicates");
+        }
+        catch (IllegalStateException e) {
+            if (dataAsList.size() == dataAsSet.size())
+                fail("Expected no ISE on input without duplicates");
+        }
+
+        exerciseMapCollection(data, toConcurrentMap(keyFn, valueFn, sum),
+                new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentHashMap.class));
+
+        exerciseMapCollection(data, toConcurrentMap(keyFn, valueFn, sum, ConcurrentSkipListMap::new),
+                new ToMapAssertion<>(keyFn, valueFn, sum, ConcurrentSkipListMap.class));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testSimpleGroupingBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+
+        // Single-level groupBy
+        exerciseMapCollection(data, groupingBy(classifier),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new ToListAssertion<>()));
+        exerciseMapCollection(data, groupingByConcurrent(classifier),
+                new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                        new ToListAssertion<>()));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                groupingBy(classifier, TreeMap::new, toCollection(HashSet::new)),
+                new GroupingByAssertion<>(classifier, TreeMap.class,
+                        new ToCollectionAssertion<Integer>(HashSet.class, false)));
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, ConcurrentSkipListMap::new,
+                        toCollection(HashSet::new)),
+                new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                        new ToCollectionAssertion<Integer>(HashSet.class, false)));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testGroupingByWithMapping(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+        Function<Integer, Integer> mapper = i -> i * 2;
+
+        exerciseMapCollection(data,
+                groupingBy(classifier, mapping(mapper, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new MappingAssertion<>(mapper,
+                                new ToListAssertion<>())));
+    }
+
+    @Test(groups = { "serialization-hostile" })
+    public void testFlatMappingClose() {
+        Function<Integer, Integer> classifier = i -> i;
+        AtomicInteger ai = new AtomicInteger();
+        Function<Integer, Stream<Integer>> flatMapper = i -> Stream.of(i, i).onClose(ai::getAndIncrement);
+        Map<Integer, List<Integer>> m = Stream.of(1, 2).collect(groupingBy(classifier, flatMapping(flatMapper, toList())));
+        assertEquals(m.size(), ai.get());
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testGroupingByWithFlatMapping(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+        Function<Integer, Stream<Integer>> flatMapperByNull = i -> null;
+        Function<Integer, Stream<Integer>> flatMapperBy0 = i -> Stream.empty();
+        Function<Integer, Stream<Integer>> flatMapperBy2 = i -> Stream.of(i, i);
+
+        exerciseMapCollection(data,
+                groupingBy(classifier, flatMapping(flatMapperByNull, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new FlatMappingAssertion<>(flatMapperBy0,
+                                new ToListAssertion<>())));
+        exerciseMapCollection(data,
+                groupingBy(classifier, flatMapping(flatMapperBy0, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new FlatMappingAssertion<>(flatMapperBy0,
+                                new ToListAssertion<>())));
+        exerciseMapCollection(data,
+                groupingBy(classifier, flatMapping(flatMapperBy2, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new FlatMappingAssertion<>(flatMapperBy2,
+                                new ToListAssertion<>())));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testGroupingByWithFiltering(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+        Predicate<Integer> filteringByMod2 = i -> i % 2 == 0;
+        Predicate<Integer> filteringByUnder100 = i -> i % 2 < 100;
+        Predicate<Integer> filteringByTrue = i -> true;
+        Predicate<Integer> filteringByFalse = i -> false;
+
+        exerciseMapCollection(data,
+                groupingBy(classifier, filtering(filteringByMod2, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new FilteringAssertion<>(filteringByMod2,
+                                new ToListAssertion<>())));
+        exerciseMapCollection(data,
+                groupingBy(classifier, filtering(filteringByUnder100, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new FilteringAssertion<>(filteringByUnder100,
+                                new ToListAssertion<>())));
+        exerciseMapCollection(data,
+                groupingBy(classifier, filtering(filteringByTrue, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new FilteringAssertion<>(filteringByTrue,
+                                new ToListAssertion<>())));
+        exerciseMapCollection(data,
+                groupingBy(classifier, filtering(filteringByFalse, toList())),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new FilteringAssertion<>(filteringByFalse,
+                                new ToListAssertion<>())));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testTwoLevelGroupingBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 6;
+        Function<Integer, Integer> classifier2 = i -> i % 23;
+
+        // Two-level groupBy
+        exerciseMapCollection(data,
+                groupingBy(classifier, groupingBy(classifier2)),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new GroupingByAssertion<>(classifier2, HashMap.class,
+                                new ToListAssertion<>())));
+        // with concurrent as upstream
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, groupingBy(classifier2)),
+                new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                        new GroupingByAssertion<>(classifier2, HashMap.class,
+                                new ToListAssertion<>())));
+        // with concurrent as downstream
+        exerciseMapCollection(data,
+                groupingBy(classifier, groupingByConcurrent(classifier2)),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new GroupingByAssertion<>(classifier2, ConcurrentHashMap.class,
+                                new ToListAssertion<>())));
+        // with concurrent as upstream and downstream
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, groupingByConcurrent(classifier2)),
+                new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                        new GroupingByAssertion<>(classifier2, ConcurrentHashMap.class,
+                                new ToListAssertion<>())));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                groupingBy(classifier, TreeMap::new, groupingBy(classifier2, TreeMap::new, toCollection(HashSet::new))),
+                new GroupingByAssertion<>(classifier, TreeMap.class,
+                        new GroupingByAssertion<>(classifier2, TreeMap.class,
+                                new ToCollectionAssertion<Integer>(HashSet.class, false))));
+        // with concurrent as upstream
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, ConcurrentSkipListMap::new, groupingBy(classifier2, TreeMap::new, toList())),
+                new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                        new GroupingByAssertion<>(classifier2, TreeMap.class,
+                                new ToListAssertion<>())));
+        // with concurrent as downstream
+        exerciseMapCollection(data,
+                groupingBy(classifier, TreeMap::new, groupingByConcurrent(classifier2, ConcurrentSkipListMap::new, toList())),
+                new GroupingByAssertion<>(classifier, TreeMap.class,
+                        new GroupingByAssertion<>(classifier2, ConcurrentSkipListMap.class,
+                                new ToListAssertion<>())));
+        // with concurrent as upstream and downstream
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, ConcurrentSkipListMap::new, groupingByConcurrent(classifier2, ConcurrentSkipListMap::new, toList())),
+                new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                        new GroupingByAssertion<>(classifier2, ConcurrentSkipListMap.class,
+                                new ToListAssertion<>())));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testGroupubgByWithReducing(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Function<Integer, Integer> classifier = i -> i % 3;
+
+        // Single-level simple reduce
+        exerciseMapCollection(data,
+                groupingBy(classifier, reducing(0, Integer::sum)),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, reducing(0, Integer::sum)),
+                new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                groupingBy(classifier, TreeMap::new, reducing(0, Integer::sum)),
+                new GroupingByAssertion<>(classifier, TreeMap.class,
+                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, ConcurrentSkipListMap::new, reducing(0, Integer::sum)),
+                new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+
+        // Single-level map-reduce
+        exerciseMapCollection(data,
+                groupingBy(classifier, reducing(0, mDoubler, Integer::sum)),
+                new GroupingByAssertion<>(classifier, HashMap.class,
+                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, reducing(0, mDoubler, Integer::sum)),
+                new GroupingByAssertion<>(classifier, ConcurrentHashMap.class,
+                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+
+        // With explicit constructors
+        exerciseMapCollection(data,
+                groupingBy(classifier, TreeMap::new, reducing(0, mDoubler, Integer::sum)),
+                new GroupingByAssertion<>(classifier, TreeMap.class,
+                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+        // with concurrent
+        exerciseMapCollection(data,
+                groupingByConcurrent(classifier, ConcurrentSkipListMap::new, reducing(0, mDoubler, Integer::sum)),
+                new GroupingByAssertion<>(classifier, ConcurrentSkipListMap.class,
+                        new ReducingAssertion<>(0, mDoubler, Integer::sum)));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testSimplePartitioningBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Predicate<Integer> classifier = i -> i % 3 == 0;
+
+        // Single-level partition to downstream List
+        exerciseMapCollection(data,
+                partitioningBy(classifier),
+                new PartitioningByAssertion<>(classifier, new ToListAssertion<>()));
+        exerciseMapCollection(data,
+                partitioningBy(classifier, toList()),
+                new PartitioningByAssertion<>(classifier, new ToListAssertion<>()));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testTwoLevelPartitioningBy(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        Predicate<Integer> classifier = i -> i % 3 == 0;
+        Predicate<Integer> classifier2 = i -> i % 7 == 0;
+
+        // Two level partition
+        exerciseMapCollection(data,
+                partitioningBy(classifier, partitioningBy(classifier2)),
+                new PartitioningByAssertion<>(classifier,
+                        new PartitioningByAssertion(classifier2, new ToListAssertion<>())));
+
+        // Two level partition with reduce
+        exerciseMapCollection(data,
+                partitioningBy(classifier, reducing(0, Integer::sum)),
+                new PartitioningByAssertion<>(classifier,
+                        new ReducingAssertion<>(0, LambdaTestHelpers.identity(), Integer::sum)));
+    }
+
+    @Test(dataProvider = "StreamTestData<Integer>", dataProviderClass = StreamTestDataProvider.class)
+    public void testComposeFinisher(String name, TestData.OfRef<Integer> data) throws ReflectiveOperationException {
+        List<Integer> asList = exerciseTerminalOps(data, s -> s.collect(toList()));
+        List<Integer> asImmutableList = exerciseTerminalOps(data, s -> s.collect(collectingAndThen(toList(), Collections::unmodifiableList)));
+        assertEquals(asList, asImmutableList);
+        try {
+            asImmutableList.add(0);
+            fail("Expecting immutable result");
+        }
+        catch (UnsupportedOperationException ignored) { }
+    }
+
+}
\ No newline at end of file
diff --git a/openjdk_java_files.bp b/openjdk_java_files.bp
index 4ace742..99971d1e 100644
--- a/openjdk_java_files.bp
+++ b/openjdk_java_files.bp
@@ -1503,6 +1503,7 @@
         "ojluni/src/main/java/sun/net/ApplicationProxy.java",
         "ojluni/src/main/java/sun/net/ConnectionResetException.java",
         "ojluni/src/main/java/sun/net/ExtendedOptionsImpl.java",
+        "ojluni/src/main/java/sun/net/ext/ExtendedSocketOptions.java",
         "ojluni/src/main/java/sun/net/ftp/FtpClient.java",
         "ojluni/src/main/java/sun/net/ftp/FtpClientProvider.java",
         "ojluni/src/main/java/sun/net/ftp/FtpDirEntry.java",