| /* |
| * Copyright (c) 2012, 2013, 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 java.util.stream; |
| |
| import java.util.HashSet; |
| import java.util.LinkedHashSet; |
| import java.util.Objects; |
| import java.util.Set; |
| import java.util.Spliterator; |
| import java.util.concurrent.ConcurrentHashMap; |
| import java.util.concurrent.atomic.AtomicBoolean; |
| import java.util.function.IntFunction; |
| |
| /** |
| * Factory methods for transforming streams into duplicate-free streams, using |
| * {@link Object#equals(Object)} to determine equality. |
| * |
| * @since 1.8 |
| */ |
| final class DistinctOps { |
| |
| private DistinctOps() { } |
| |
| /** |
| * Appends a "distinct" operation to the provided stream, and returns the |
| * new stream. |
| * |
| * @param <T> the type of both input and output elements |
| * @param upstream a reference stream with element type T |
| * @return the new stream |
| */ |
| static <T> ReferencePipeline<T, T> makeRef(AbstractPipeline<?, T, ?> upstream) { |
| return new ReferencePipeline.StatefulOp<T, T>(upstream, StreamShape.REFERENCE, |
| StreamOpFlag.IS_DISTINCT | StreamOpFlag.NOT_SIZED) { |
| |
| <P_IN> Node<T> reduce(PipelineHelper<T> helper, Spliterator<P_IN> spliterator) { |
| // If the stream is SORTED then it should also be ORDERED so the following will also |
| // preserve the sort order |
| TerminalOp<T, LinkedHashSet<T>> reduceOp |
| = ReduceOps.<T, LinkedHashSet<T>>makeRef(LinkedHashSet::new, LinkedHashSet::add, |
| LinkedHashSet::addAll); |
| return Nodes.node(reduceOp.evaluateParallel(helper, spliterator)); |
| } |
| |
| @Override |
| <P_IN> Node<T> opEvaluateParallel(PipelineHelper<T> helper, |
| Spliterator<P_IN> spliterator, |
| IntFunction<T[]> generator) { |
| if (StreamOpFlag.DISTINCT.isKnown(helper.getStreamAndOpFlags())) { |
| // No-op |
| return helper.evaluate(spliterator, false, generator); |
| } |
| else if (StreamOpFlag.ORDERED.isKnown(helper.getStreamAndOpFlags())) { |
| return reduce(helper, spliterator); |
| } |
| else { |
| // Holder of null state since ConcurrentHashMap does not support null values |
| AtomicBoolean seenNull = new AtomicBoolean(false); |
| ConcurrentHashMap<T, Boolean> map = new ConcurrentHashMap<>(); |
| TerminalOp<T, Void> forEachOp = ForEachOps.makeRef(t -> { |
| if (t == null) |
| seenNull.set(true); |
| else |
| map.putIfAbsent(t, Boolean.TRUE); |
| }, false); |
| forEachOp.evaluateParallel(helper, spliterator); |
| |
| // If null has been seen then copy the key set into a HashSet that supports null values |
| // and add null |
| Set<T> keys = map.keySet(); |
| if (seenNull.get()) { |
| // TODO Implement a more efficient set-union view, rather than copying |
| keys = new HashSet<>(keys); |
| keys.add(null); |
| } |
| return Nodes.node(keys); |
| } |
| } |
| |
| @Override |
| <P_IN> Spliterator<T> opEvaluateParallelLazy(PipelineHelper<T> helper, Spliterator<P_IN> spliterator) { |
| if (StreamOpFlag.DISTINCT.isKnown(helper.getStreamAndOpFlags())) { |
| // No-op |
| return helper.wrapSpliterator(spliterator); |
| } |
| else if (StreamOpFlag.ORDERED.isKnown(helper.getStreamAndOpFlags())) { |
| // Not lazy, barrier required to preserve order |
| return reduce(helper, spliterator).spliterator(); |
| } |
| else { |
| // Lazy |
| return new StreamSpliterators.DistinctSpliterator<>(helper.wrapSpliterator(spliterator)); |
| } |
| } |
| |
| @Override |
| Sink<T> opWrapSink(int flags, Sink<T> sink) { |
| Objects.requireNonNull(sink); |
| |
| if (StreamOpFlag.DISTINCT.isKnown(flags)) { |
| return sink; |
| } else if (StreamOpFlag.SORTED.isKnown(flags)) { |
| return new Sink.ChainedReference<T, T>(sink) { |
| boolean seenNull; |
| T lastSeen; |
| |
| @Override |
| public void begin(long size) { |
| seenNull = false; |
| lastSeen = null; |
| downstream.begin(-1); |
| } |
| |
| @Override |
| public void end() { |
| seenNull = false; |
| lastSeen = null; |
| downstream.end(); |
| } |
| |
| @Override |
| public void accept(T t) { |
| if (t == null) { |
| if (!seenNull) { |
| seenNull = true; |
| downstream.accept(lastSeen = null); |
| } |
| } else if (lastSeen == null || !t.equals(lastSeen)) { |
| downstream.accept(lastSeen = t); |
| } |
| } |
| }; |
| } else { |
| return new Sink.ChainedReference<T, T>(sink) { |
| Set<T> seen; |
| |
| @Override |
| public void begin(long size) { |
| seen = new HashSet<>(); |
| downstream.begin(-1); |
| } |
| |
| @Override |
| public void end() { |
| seen = null; |
| downstream.end(); |
| } |
| |
| @Override |
| public void accept(T t) { |
| if (!seen.contains(t)) { |
| seen.add(t); |
| downstream.accept(t); |
| } |
| } |
| }; |
| } |
| } |
| }; |
| } |
| } |