diff --git a/luni/src/main/java/java/io/BufferedReader.java b/luni/src/main/java/java/io/BufferedReader.java
index 5f2484b..9fba039 100644
--- a/luni/src/main/java/java/io/BufferedReader.java
+++ b/luni/src/main/java/java/io/BufferedReader.java
@@ -190,7 +190,7 @@
     @Override
     public void mark(int markLimit) throws IOException {
         if (markLimit < 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("markLimit < 0:" + markLimit);
         }
         synchronized (lock) {
             checkNotClosed();
diff --git a/luni/src/main/java/java/io/StringReader.java b/luni/src/main/java/java/io/StringReader.java
index 9f8ff13..5579d62 100644
--- a/luni/src/main/java/java/io/StringReader.java
+++ b/luni/src/main/java/java/io/StringReader.java
@@ -83,7 +83,7 @@
     @Override
     public void mark(int readLimit) throws IOException {
         if (readLimit < 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("readLimit < 0: " + readLimit);
         }
 
         synchronized (lock) {
diff --git a/luni/src/main/java/java/io/StringWriter.java b/luni/src/main/java/java/io/StringWriter.java
index f0b1d18..2946483 100644
--- a/luni/src/main/java/java/io/StringWriter.java
+++ b/luni/src/main/java/java/io/StringWriter.java
@@ -49,11 +49,11 @@
      * writer.
      *
      * @param initialSize
-     *            the intial size of the target string buffer.
+     *            the initial size of the target string buffer.
      */
     public StringWriter(int initialSize) {
         if (initialSize < 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("initialSize < 0: " + initialSize);
         }
         buf = new StringBuffer(initialSize);
         lock = buf;
diff --git a/luni/src/main/java/java/lang/System.java b/luni/src/main/java/java/lang/System.java
index f8f9146..75a390c 100644
--- a/luni/src/main/java/java/lang/System.java
+++ b/luni/src/main/java/java/lang/System.java
@@ -412,58 +412,44 @@
     /**
      * Returns the value of a particular system property. The {@code
      * defaultValue} will be returned if no such property has been found.
-     *
-     * @param prop
-     *            the name of the system property to look up.
-     * @param defaultValue
-     *            the return value if the system property with the given name
-     *            does not exist.
-     * @return the value of the specified system property or the {@code
-     *         defaultValue} if the property does not exist.
      */
-    public static String getProperty(String prop, String defaultValue) {
-        if (prop.isEmpty()) {
-            throw new IllegalArgumentException();
-        }
-        return getProperties().getProperty(prop, defaultValue);
+    public static String getProperty(String name, String defaultValue) {
+        checkPropertyName(name);
+        return getProperties().getProperty(name, defaultValue);
     }
 
     /**
      * Sets the value of a particular system property.
      *
-     * @param prop
-     *            the name of the system property to be changed.
-     * @param value
-     *            the value to associate with the given property {@code prop}.
      * @return the old value of the property or {@code null} if the property
      *         didn't exist.
      */
-    public static String setProperty(String prop, String value) {
-        if (prop.isEmpty()) {
-            throw new IllegalArgumentException();
-        }
-        return (String) getProperties().setProperty(prop, value);
+    public static String setProperty(String name, String value) {
+        checkPropertyName(name);
+        return (String) getProperties().setProperty(name, value);
     }
 
     /**
      * Removes a specific system property.
      *
-     * @param key
-     *            the name of the system property to be removed.
      * @return the property value or {@code null} if the property didn't exist.
      * @throws NullPointerException
-     *             if the argument {@code key} is {@code null}.
+     *             if the argument is {@code null}.
      * @throws IllegalArgumentException
-     *             if the argument {@code key} is empty.
+     *             if the argument is empty.
      */
-    public static String clearProperty(String key) {
-        if (key == null) {
-            throw new NullPointerException("key == null");
+    public static String clearProperty(String name) {
+        checkPropertyName(name);
+        return (String) getProperties().remove(name);
+    }
+
+    private static void checkPropertyName(String name) {
+        if (name == null) {
+            throw new NullPointerException("name == null");
         }
-        if (key.isEmpty()) {
-            throw new IllegalArgumentException();
+        if (name.isEmpty()) {
+            throw new IllegalArgumentException("name is empty");
         }
-        return (String) getProperties().remove(key);
     }
 
     /**
diff --git a/luni/src/main/java/java/lang/Thread.java b/luni/src/main/java/java/lang/Thread.java
index a076a04..cc0975f 100644
--- a/luni/src/main/java/java/lang/Thread.java
+++ b/luni/src/main/java/java/lang/Thread.java
@@ -779,7 +779,7 @@
      */
     public final void join(long millis, int nanos) throws InterruptedException {
         if (millis < 0 || nanos < 0 || nanos >= NANOS_PER_MILLI) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("bad timeout: millis=" + millis + ",nanos=" + nanos);
         }
 
         // avoid overflow: if total > 292,277 years, just wait forever
diff --git a/luni/src/main/java/java/net/DatagramSocket.java b/luni/src/main/java/java/net/DatagramSocket.java
index c01f3af..790ebc9 100644
--- a/luni/src/main/java/java/net/DatagramSocket.java
+++ b/luni/src/main/java/java/net/DatagramSocket.java
@@ -614,7 +614,7 @@
     public void setTrafficClass(int value) throws SocketException {
         checkOpen();
         if (value < 0 || value > 255) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Value doesn't fit in an unsigned byte: " + value);
         }
         impl.setOption(SocketOptions.IP_TOS, Integer.valueOf(value));
     }
diff --git a/luni/src/main/java/java/net/HttpCookie.java b/luni/src/main/java/java/net/HttpCookie.java
index 057afef..ce1a8d2 100644
--- a/luni/src/main/java/java/net/HttpCookie.java
+++ b/luni/src/main/java/java/net/HttpCookie.java
@@ -445,7 +445,7 @@
     public HttpCookie(String name, String value) {
         String ntrim = name.trim(); // erase leading and trailing whitespace
         if (!isValidName(ntrim)) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Invalid name: " + name);
         }
 
         this.name = ntrim;
@@ -650,11 +650,11 @@
      *
      * @throws IllegalArgumentException if v is neither 0 nor 1
      */
-    public void setVersion(int v) {
-        if (v != 0 && v != 1) {
-            throw new IllegalArgumentException();
+    public void setVersion(int newVersion) {
+        if (newVersion != 0 && newVersion != 1) {
+            throw new IllegalArgumentException("Bad version: " + newVersion);
         }
-        version = v;
+        version = newVersion;
     }
 
     @Override public Object clone() {
diff --git a/luni/src/main/java/java/net/Socket.java b/luni/src/main/java/java/net/Socket.java
index 7661f28..a9e0bc3 100644
--- a/luni/src/main/java/java/net/Socket.java
+++ b/luni/src/main/java/java/net/Socket.java
@@ -909,7 +909,7 @@
     public void setTrafficClass(int value) throws SocketException {
         checkOpenAndCreate(true);
         if (value < 0 || value > 255) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Value doesn't fit in an unsigned byte: " + value);
         }
         impl.setOption(SocketOptions.IP_TOS, Integer.valueOf(value));
     }
diff --git a/luni/src/main/java/java/net/URISyntaxException.java b/luni/src/main/java/java/net/URISyntaxException.java
index 957ea31..70fe6a1 100644
--- a/luni/src/main/java/java/net/URISyntaxException.java
+++ b/luni/src/main/java/java/net/URISyntaxException.java
@@ -56,7 +56,7 @@
         }
 
         if (index < -1) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Bad index: " + index);
         }
 
         this.input = input;
diff --git a/luni/src/main/java/java/nio/DatagramChannelImpl.java b/luni/src/main/java/java/nio/DatagramChannelImpl.java
index 4d2fc5a..a23010e 100644
--- a/luni/src/main/java/java/nio/DatagramChannelImpl.java
+++ b/luni/src/main/java/java/nio/DatagramChannelImpl.java
@@ -253,7 +253,8 @@
         }
 
         if (isConnected() && !connectAddress.equals(isa)) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Connected to " + connectAddress +
+                                               ", not " + socketAddress);
         }
 
         synchronized (writeLock) {
diff --git a/luni/src/main/java/java/nio/channels/spi/AbstractSelectableChannel.java b/luni/src/main/java/java/nio/channels/spi/AbstractSelectableChannel.java
index 4035090..1c7e190 100644
--- a/luni/src/main/java/java/nio/channels/spi/AbstractSelectableChannel.java
+++ b/luni/src/main/java/java/nio/channels/spi/AbstractSelectableChannel.java
@@ -130,7 +130,7 @@
             throw new ClosedChannelException();
         }
         if (!((interestSet & ~validOps()) == 0)) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("no valid ops in interest set: " + interestSet);
         }
 
         synchronized (blockingLock) {
diff --git a/luni/src/main/java/java/security/AlgorithmParameterGenerator.java b/luni/src/main/java/java/security/AlgorithmParameterGenerator.java
index 3edc167..61548d7 100644
--- a/luni/src/main/java/java/security/AlgorithmParameterGenerator.java
+++ b/luni/src/main/java/java/security/AlgorithmParameterGenerator.java
@@ -146,7 +146,7 @@
     public static AlgorithmParameterGenerator getInstance(String algorithm,
             Provider provider) throws NoSuchAlgorithmException {
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         if (algorithm == null) {
             throw new NullPointerException("algorithm == null");
diff --git a/luni/src/main/java/java/security/KeyFactory.java b/luni/src/main/java/java/security/KeyFactory.java
index 8d39003..3bd05b9 100644
--- a/luni/src/main/java/java/security/KeyFactory.java
+++ b/luni/src/main/java/java/security/KeyFactory.java
@@ -127,7 +127,7 @@
     public static KeyFactory getInstance(String algorithm, Provider provider)
                                  throws NoSuchAlgorithmException {
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         if (algorithm == null) {
             throw new NullPointerException("algorithm == null");
diff --git a/luni/src/main/java/java/security/KeyPairGenerator.java b/luni/src/main/java/java/security/KeyPairGenerator.java
index 5c17d79..8a713d0 100644
--- a/luni/src/main/java/java/security/KeyPairGenerator.java
+++ b/luni/src/main/java/java/security/KeyPairGenerator.java
@@ -140,7 +140,7 @@
     public static KeyPairGenerator getInstance(String algorithm,
             Provider provider) throws NoSuchAlgorithmException {
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         if (algorithm == null) {
             throw new NullPointerException("algorithm == null");
diff --git a/luni/src/main/java/java/security/KeyStore.java b/luni/src/main/java/java/security/KeyStore.java
index 020010e..b0e4945 100644
--- a/luni/src/main/java/java/security/KeyStore.java
+++ b/luni/src/main/java/java/security/KeyStore.java
@@ -179,7 +179,7 @@
     public static KeyStore getInstance(String type, Provider provider) throws KeyStoreException {
         // check parameters
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         if (type == null) {
             throw new NullPointerException("type == null");
diff --git a/luni/src/main/java/java/security/MessageDigest.java b/luni/src/main/java/java/security/MessageDigest.java
index 6f1bf21..658b41f 100644
--- a/luni/src/main/java/java/security/MessageDigest.java
+++ b/luni/src/main/java/java/security/MessageDigest.java
@@ -149,7 +149,7 @@
     public static MessageDigest getInstance(String algorithm, Provider provider)
             throws NoSuchAlgorithmException {
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         if (algorithm == null) {
             throw new NullPointerException("algorithm == null");
diff --git a/luni/src/main/java/java/security/SecureRandom.java b/luni/src/main/java/java/security/SecureRandom.java
index 798f0e6..281885b 100644
--- a/luni/src/main/java/java/security/SecureRandom.java
+++ b/luni/src/main/java/java/security/SecureRandom.java
@@ -207,7 +207,7 @@
     public static SecureRandom getInstance(String algorithm, Provider provider)
             throws NoSuchAlgorithmException {
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         if (algorithm == null) {
             throw new NullPointerException("algorithm == null");
diff --git a/luni/src/main/java/java/security/Signature.java b/luni/src/main/java/java/security/Signature.java
index be89654..b2bd122 100644
--- a/luni/src/main/java/java/security/Signature.java
+++ b/luni/src/main/java/java/security/Signature.java
@@ -168,7 +168,7 @@
             throw new NullPointerException("algorithm == null");
         }
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         return getSignatureInstance(algorithm, provider);
     }
diff --git a/luni/src/main/java/java/security/cert/CertPathValidator.java b/luni/src/main/java/java/security/cert/CertPathValidator.java
index fda3aeb..a3a666a 100644
--- a/luni/src/main/java/java/security/cert/CertPathValidator.java
+++ b/luni/src/main/java/java/security/cert/CertPathValidator.java
@@ -157,7 +157,7 @@
     public static CertPathValidator getInstance(String algorithm,
             Provider provider) throws NoSuchAlgorithmException {
         if (provider == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("provider == null");
         }
         if (algorithm == null) {
             throw new NullPointerException("algorithm == null");
diff --git a/luni/src/main/java/java/sql/Date.java b/luni/src/main/java/java/sql/Date.java
index 2434fbd..34ca5bd 100644
--- a/luni/src/main/java/java/sql/Date.java
+++ b/luni/src/main/java/java/sql/Date.java
@@ -81,7 +81,7 @@
     @Deprecated
     @Override
     public int getHours() {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -94,7 +94,7 @@
     @Deprecated
     @Override
     public int getMinutes() {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -107,7 +107,7 @@
     @Deprecated
     @Override
     public int getSeconds() {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -121,7 +121,7 @@
     @Deprecated
     @Override
     public void setHours(int theHours) {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -135,7 +135,7 @@
     @Deprecated
     @Override
     public void setMinutes(int theMinutes) {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -149,7 +149,7 @@
     @Deprecated
     @Override
     public void setSeconds(int theSeconds) {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -212,7 +212,7 @@
      */
     public static Date valueOf(String dateString) {
         if (dateString == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("dateString == null");
         }
         int firstIndex = dateString.indexOf('-');
         int secondIndex = dateString.indexOf('-', firstIndex + 1);
diff --git a/luni/src/main/java/java/sql/Time.java b/luni/src/main/java/java/sql/Time.java
index bccce68..913379c 100644
--- a/luni/src/main/java/java/sql/Time.java
+++ b/luni/src/main/java/java/sql/Time.java
@@ -76,7 +76,7 @@
     @Deprecated
     @Override
     public int getDate() {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -90,7 +90,7 @@
     @Deprecated
     @Override
     public int getDay() {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -104,7 +104,7 @@
     @Deprecated
     @Override
     public int getMonth() {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -118,7 +118,7 @@
     @Deprecated
     @Override
     public int getYear() {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -131,7 +131,7 @@
     @Deprecated
     @Override
     public void setDate(int i) {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -144,7 +144,7 @@
     @Deprecated
     @Override
     public void setMonth(int i) {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -157,7 +157,7 @@
     @Deprecated
     @Override
     public void setYear(int i) {
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("unimplemented");
     }
 
     /**
@@ -223,7 +223,7 @@
      */
     public static Time valueOf(String timeString) {
         if (timeString == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("timeString == null");
         }
         int firstIndex = timeString.indexOf(':');
         int secondIndex = timeString.indexOf(':', firstIndex + 1);
diff --git a/luni/src/main/java/java/sql/Timestamp.java b/luni/src/main/java/java/sql/Timestamp.java
index 070e86f..2e6d3d9 100644
--- a/luni/src/main/java/java/sql/Timestamp.java
+++ b/luni/src/main/java/java/sql/Timestamp.java
@@ -83,7 +83,7 @@
             throws IllegalArgumentException {
         super(theYear, theMonth, theDate, theHour, theMinute, theSecond);
         if (theNano < 0 || theNano > 999999999) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("ns out of range: " + theNano);
         }
         nanos = theNano;
     }
diff --git a/luni/src/main/java/java/text/AttributedString.java b/luni/src/main/java/java/text/AttributedString.java
index d679283..289ad6d 100644
--- a/luni/src/main/java/java/text/AttributedString.java
+++ b/luni/src/main/java/java/text/AttributedString.java
@@ -577,8 +577,8 @@
         if (attribute == null) {
             throw new NullPointerException("attribute == null");
         }
-        if (text.length() == 0) {
-            throw new IllegalArgumentException();
+        if (text.isEmpty()) {
+            throw new IllegalArgumentException("text is empty");
         }
 
         List<Range> ranges = attributeMap.get(attribute);
diff --git a/luni/src/main/java/java/text/ChoiceFormat.java b/luni/src/main/java/java/text/ChoiceFormat.java
index e0a1239..014b8c7 100644
--- a/luni/src/main/java/java/text/ChoiceFormat.java
+++ b/luni/src/main/java/java/text/ChoiceFormat.java
@@ -168,10 +168,10 @@
                     next = nextDouble(value.doubleValue());
                     break;
                 default:
-                    throw new IllegalArgumentException();
+                    throw new IllegalArgumentException("Bad character '" + ch + "' in template: " + template);
             }
             if (limitCount > 0 && next <= limits[limitCount - 1]) {
-                throw new IllegalArgumentException();
+                throw new IllegalArgumentException("Bad template: " + template);
             }
             buffer.setLength(0);
             position.setIndex(index);
@@ -426,7 +426,8 @@
      */
     public void setChoices(double[] limits, String[] formats) {
         if (limits.length != formats.length) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("limits.length != formats.length: " +
+                                               limits.length + " != " + formats.length);
         }
         choiceLimits = limits;
         choiceFormats = formats;
diff --git a/luni/src/main/java/java/text/Collator.java b/luni/src/main/java/java/text/Collator.java
index 2ddb516..58d7047 100644
--- a/luni/src/main/java/java/text/Collator.java
+++ b/luni/src/main/java/java/text/Collator.java
@@ -339,7 +339,7 @@
         case Collator.NO_DECOMPOSITION:
             return RuleBasedCollatorICU.VALUE_OFF;
         }
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("Bad mode: " + mode);
     }
 
     private int decompositionMode_ICU_Java(int mode) {
@@ -366,7 +366,7 @@
         case Collator.IDENTICAL:
             return RuleBasedCollatorICU.VALUE_IDENTICAL;
         }
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("Bad strength: " + value);
     }
 
     private int strength_ICU_Java(int value) {
diff --git a/luni/src/main/java/java/text/DateFormat.java b/luni/src/main/java/java/text/DateFormat.java
index 8441b59..ac64eed 100644
--- a/luni/src/main/java/java/text/DateFormat.java
+++ b/luni/src/main/java/java/text/DateFormat.java
@@ -286,16 +286,14 @@
      *            {@code Number} instance.
      */
     @Override
-    public final StringBuffer format(Object object, StringBuffer buffer,
-            FieldPosition field) {
+    public final StringBuffer format(Object object, StringBuffer buffer, FieldPosition field) {
         if (object instanceof Date) {
             return format((Date) object, buffer, field);
         }
         if (object instanceof Number) {
-            return format(new Date(((Number) object).longValue()), buffer,
-                    field);
+            return format(new Date(((Number) object).longValue()), buffer, field);
         }
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("Bad class: " + object.getClass());
     }
 
     /**
@@ -306,8 +304,7 @@
      * @return the formatted string.
      */
     public final String format(Date date) {
-        return format(date, new StringBuffer(), new FieldPosition(0))
-                .toString();
+        return format(date, new StringBuffer(), new FieldPosition(0)).toString();
     }
 
     /**
@@ -328,8 +325,7 @@
      *            of the alignment field in the formatted text.
      * @return the string buffer.
      */
-    public abstract StringBuffer format(Date date, StringBuffer buffer,
-            FieldPosition field);
+    public abstract StringBuffer format(Date date, StringBuffer buffer, FieldPosition field);
 
     /**
      * Returns an array of locales for which custom {@code DateFormat} instances
@@ -811,9 +807,8 @@
          */
         public static Field ofCalendarField(int calendarField) {
             if (calendarField < 0 || calendarField >= Calendar.FIELD_COUNT) {
-                throw new IllegalArgumentException();
+                throw new IllegalArgumentException("Field out of range: " + calendarField);
             }
-
             return table.get(Integer.valueOf(calendarField));
         }
     }
@@ -821,14 +816,14 @@
     private static void checkDateStyle(int style) {
         if (!(style == SHORT || style == MEDIUM || style == LONG
                 || style == FULL || style == DEFAULT)) {
-            throw new IllegalArgumentException("Illegal date style " + style);
+            throw new IllegalArgumentException("Illegal date style: " + style);
         }
     }
 
     private static void checkTimeStyle(int style) {
         if (!(style == SHORT || style == MEDIUM || style == LONG
                 || style == FULL || style == DEFAULT)) {
-            throw new IllegalArgumentException("Illegal time style " + style);
+            throw new IllegalArgumentException("Illegal time style: " + style);
         }
     }
 }
diff --git a/luni/src/main/java/java/text/NumberFormat.java b/luni/src/main/java/java/text/NumberFormat.java
index c285e3d..36fdd0f 100644
--- a/luni/src/main/java/java/text/NumberFormat.java
+++ b/luni/src/main/java/java/text/NumberFormat.java
@@ -301,7 +301,7 @@
             double dv = ((Number) object).doubleValue();
             return format(dv, buffer, field);
         }
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("Bad class: " + object.getClass());
     }
 
     /**
diff --git a/luni/src/main/java/java/text/SimpleDateFormat.java b/luni/src/main/java/java/text/SimpleDateFormat.java
index d845d45..b856d7a 100644
--- a/luni/src/main/java/java/text/SimpleDateFormat.java
+++ b/luni/src/main/java/java/text/SimpleDateFormat.java
@@ -480,8 +480,7 @@
         if (object instanceof Number) {
             return formatToCharacterIteratorImpl(new Date(((Number) object).longValue()));
         }
-        throw new IllegalArgumentException();
-
+        throw new IllegalArgumentException("Bad class: " + object.getClass());
     }
 
     private AttributedCharacterIterator formatToCharacterIteratorImpl(Date date) {
diff --git a/luni/src/main/java/java/util/ArrayList.java b/luni/src/main/java/java/util/ArrayList.java
index dc7b198..d193eec 100644
--- a/luni/src/main/java/java/util/ArrayList.java
+++ b/luni/src/main/java/java/util/ArrayList.java
@@ -70,7 +70,7 @@
      */
     public ArrayList(int capacity) {
         if (capacity < 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("capacity < 0: " + capacity);
         }
         array = (capacity == 0 ? EmptyArray.OBJECT : new Object[capacity]);
     }
diff --git a/luni/src/main/java/java/util/Collections.java b/luni/src/main/java/java/util/Collections.java
index d49ca85..0fafcff 100644
--- a/luni/src/main/java/java/util/Collections.java
+++ b/luni/src/main/java/java/util/Collections.java
@@ -63,7 +63,7 @@
 
         CopiesList(int length, E object) {
             if (length < 0) {
-                throw new IllegalArgumentException();
+                throw new IllegalArgumentException("length < 0: " + length);
             }
             n = length;
             element = object;
@@ -2648,7 +2648,7 @@
         if (map.isEmpty()) {
             return new SetFromMap<E>(map);
         }
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("map not empty");
     }
 
     /**
diff --git a/luni/src/main/java/java/util/Date.java b/luni/src/main/java/java/util/Date.java
index b639003..da9f296 100644
--- a/luni/src/main/java/java/util/Date.java
+++ b/luni/src/main/java/java/util/Date.java
@@ -363,6 +363,10 @@
         return -1;
     }
 
+    private static IllegalArgumentException parseError(String string) {
+        throw new IllegalArgumentException("Parse error: " + string);
+    }
+
     /**
      * Returns the millisecond value of the date and time parsed from the
      * specified {@code String}. Many date/time formats are recognized, including IETF
@@ -413,7 +417,7 @@
             } else if ('0' <= next && next <= '9') {
                 nextState = NUMBERS;
             } else if (!Character.isSpace(next) && ",+-:/".indexOf(next) == -1) {
-                throw new IllegalArgumentException();
+                throw parseError(string);
             }
 
             if (state == NUMBERS && nextState != NUMBERS) {
@@ -433,7 +437,7 @@
                         zoneOffset = sign == '-' ? -digit : digit;
                         sign = 0;
                     } else {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                 } else if (digit >= 70) {
                     if (year == -1
@@ -441,7 +445,7 @@
                                     || next == '/' || next == '\r')) {
                         year = digit;
                     } else {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                 } else if (next == ':') {
                     if (hour == -1) {
@@ -449,7 +453,7 @@
                     } else if (minute == -1) {
                         minute = digit;
                     } else {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                 } else if (next == '/') {
                     if (month == -1) {
@@ -457,7 +461,7 @@
                     } else if (date == -1) {
                         date = digit;
                     } else {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                 } else if (Character.isSpace(next) || next == ','
                         || next == '-' || next == '\r') {
@@ -470,30 +474,30 @@
                     } else if (year == -1) {
                         year = digit;
                     } else {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                 } else if (year == -1 && month != -1 && date != -1) {
                     year = digit;
                 } else {
-                    throw new IllegalArgumentException();
+                    throw parseError(string);
                 }
             } else if (state == LETTERS && nextState != LETTERS) {
                 String text = buffer.toString().toUpperCase(Locale.US);
                 buffer.setLength(0);
                 if (text.length() == 1) {
-                    throw new IllegalArgumentException();
+                    throw parseError(string);
                 }
                 if (text.equals("AM")) {
                     if (hour == 12) {
                         hour = 0;
                     } else if (hour < 1 || hour > 12) {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                 } else if (text.equals("PM")) {
                     if (hour == 12) {
                         hour = 0;
                     } else if (hour < 1 || hour > 12) {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                     hour += 12;
                 } else {
@@ -510,7 +514,7 @@
                         zone = true;
                         zoneOffset = value;
                     } else {
-                        throw new IllegalArgumentException();
+                        throw parseError(string);
                     }
                 }
             }
@@ -556,7 +560,7 @@
             return new Date(year - 1900, month, date, hour, minute, second)
                     .getTime();
         }
-        throw new IllegalArgumentException();
+        throw parseError(string);
     }
 
     /**
diff --git a/luni/src/main/java/java/util/EnumMap.java b/luni/src/main/java/java/util/EnumMap.java
index a721ee3..827fb51 100644
--- a/luni/src/main/java/java/util/EnumMap.java
+++ b/luni/src/main/java/java/util/EnumMap.java
@@ -436,8 +436,8 @@
         if (map instanceof EnumMap) {
             initialization((EnumMap<K, V>) map);
         } else {
-            if (map.size() == 0) {
-                throw new IllegalArgumentException();
+            if (map.isEmpty()) {
+                throw new IllegalArgumentException("map is empty");
             }
             Iterator<K> iter = map.keySet().iterator();
             K enumKey = iter.next();
diff --git a/luni/src/main/java/java/util/EnumSet.java b/luni/src/main/java/java/util/EnumSet.java
index cc8969e..20be6f7 100644
--- a/luni/src/main/java/java/util/EnumSet.java
+++ b/luni/src/main/java/java/util/EnumSet.java
@@ -104,7 +104,7 @@
             return copyOf((EnumSet<E>) c);
         }
         if (c.isEmpty()) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("empty collection");
         }
         Iterator<E> iterator = c.iterator();
         E element = iterator.next();
@@ -284,7 +284,7 @@
      */
     public static <E extends Enum<E>> EnumSet<E> range(E start, E end) {
         if (start.compareTo(end) > 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("start is behind end");
         }
         EnumSet<E> set = EnumSet.noneOf(start.getDeclaringClass());
         set.setRange(start, end);
diff --git a/luni/src/main/java/java/util/EventObject.java b/luni/src/main/java/java/util/EventObject.java
index 058e7e8..0fc92bb 100644
--- a/luni/src/main/java/java/util/EventObject.java
+++ b/luni/src/main/java/java/util/EventObject.java
@@ -41,7 +41,7 @@
      */
     public EventObject(Object source) {
         if (source == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("source == null");
         }
         this.source = source;
     }
diff --git a/luni/src/main/java/java/util/IdentityHashMap.java b/luni/src/main/java/java/util/IdentityHashMap.java
index e693f7d..904eed5 100644
--- a/luni/src/main/java/java/util/IdentityHashMap.java
+++ b/luni/src/main/java/java/util/IdentityHashMap.java
@@ -261,13 +261,12 @@
      *            this map.
      */
     public IdentityHashMap(int maxSize) {
-        if (maxSize >= 0) {
-            this.size = 0;
-            threshold = getThreshold(maxSize);
-            elementData = newElementArray(computeElementArraySize());
-        } else {
-            throw new IllegalArgumentException();
+        if (maxSize < 0) {
+            throw new IllegalArgumentException("maxSize < 0: " + maxSize);
         }
+        size = 0;
+        threshold = getThreshold(maxSize);
+        elementData = newElementArray(computeElementArraySize());
     }
 
     private int getThreshold(int maxSize) {
diff --git a/luni/src/main/java/java/util/PriorityQueue.java b/luni/src/main/java/java/util/PriorityQueue.java
index e09eb05..cc9bfe6 100644
--- a/luni/src/main/java/java/util/PriorityQueue.java
+++ b/luni/src/main/java/java/util/PriorityQueue.java
@@ -82,7 +82,7 @@
      */
     public PriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
         if (initialCapacity < 1) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("initialCapacity < 1: " + initialCapacity);
         }
         elements = newElementArray(initialCapacity);
         this.comparator = comparator;
diff --git a/luni/src/main/java/java/util/Random.java b/luni/src/main/java/java/util/Random.java
index b0a92ff..4a67244 100644
--- a/luni/src/main/java/java/util/Random.java
+++ b/luni/src/main/java/java/util/Random.java
@@ -171,18 +171,18 @@
      * in the half-open range [0, n).
      */
     public int nextInt(int n) {
-        if (n > 0) {
-            if ((n & -n) == n) {
-                return (int) ((n * (long) next(31)) >> 31);
-            }
-            int bits, val;
-            do {
-                bits = next(31);
-                val = bits % n;
-            } while (bits - val + (n - 1) < 0);
-            return val;
+        if (n <= 0) {
+            throw new IllegalArgumentException("n <= 0: " + n);
         }
-        throw new IllegalArgumentException();
+        if ((n & -n) == n) {
+            return (int) ((n * (long) next(31)) >> 31);
+        }
+        int bits, val;
+        do {
+            bits = next(31);
+            val = bits % n;
+        } while (bits - val + (n - 1) < 0);
+        return val;
     }
 
     /**
diff --git a/luni/src/main/java/java/util/SimpleTimeZone.java b/luni/src/main/java/java/util/SimpleTimeZone.java
index 93dc88e..0675480 100644
--- a/luni/src/main/java/java/util/SimpleTimeZone.java
+++ b/luni/src/main/java/java/util/SimpleTimeZone.java
@@ -546,11 +546,10 @@
      *            the daylight savings offset in milliseconds.
      */
     public void setDSTSavings(int milliseconds) {
-        if (milliseconds > 0) {
-            dstSavings = milliseconds;
-        } else {
-            throw new IllegalArgumentException();
+        if (milliseconds <= 0) {
+            throw new IllegalArgumentException("milliseconds <= 0: " + milliseconds);
         }
+        dstSavings = milliseconds;
     }
 
     private void checkRange(int month, int dayOfWeek, int time) {
diff --git a/luni/src/main/java/java/util/TimeZone.java b/luni/src/main/java/java/util/TimeZone.java
index a5e0ad7..9a76fc7 100644
--- a/luni/src/main/java/java/util/TimeZone.java
+++ b/luni/src/main/java/java/util/TimeZone.java
@@ -168,7 +168,7 @@
      */
     public String getDisplayName(boolean daylightTime, int style, Locale locale) {
         if (style != SHORT && style != LONG) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Bad style: " + style);
         }
 
         boolean useDaylight = daylightTime && useDaylightTime();
diff --git a/luni/src/main/java/java/util/Timer.java b/luni/src/main/java/java/util/Timer.java
index afc745c..25ac432 100644
--- a/luni/src/main/java/java/util/Timer.java
+++ b/luni/src/main/java/java/util/Timer.java
@@ -433,7 +433,7 @@
      */
     public void schedule(TimerTask task, Date when) {
         if (when.getTime() < 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("when < 0: " + when.getTime());
         }
         long delay = when.getTime() - System.currentTimeMillis();
         scheduleImpl(task, delay < 0 ? 0 : delay, -1, false);
@@ -454,7 +454,7 @@
      */
     public void schedule(TimerTask task, long delay) {
         if (delay < 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("delay < 0: " + delay);
         }
         scheduleImpl(task, delay, -1, false);
     }
diff --git a/luni/src/main/java/java/util/Vector.java b/luni/src/main/java/java/util/Vector.java
index f8a456d..65e135a 100644
--- a/luni/src/main/java/java/util/Vector.java
+++ b/luni/src/main/java/java/util/Vector.java
@@ -92,7 +92,7 @@
      */
     public Vector(int capacity, int capacityIncrement) {
         if (capacity < 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("capacity < 0: " + capacity);
         }
         elementData = newElementArray(capacity);
         elementCount = 0;
diff --git a/luni/src/main/java/java/util/WeakHashMap.java b/luni/src/main/java/java/util/WeakHashMap.java
index 6417679..2c07d28 100644
--- a/luni/src/main/java/java/util/WeakHashMap.java
+++ b/luni/src/main/java/java/util/WeakHashMap.java
@@ -198,15 +198,14 @@
      *                if the capacity is less than zero.
      */
     public WeakHashMap(int capacity) {
-        if (capacity >= 0) {
-            elementCount = 0;
-            elementData = newEntryArray(capacity == 0 ? 1 : capacity);
-            loadFactor = 7500; // Default load factor of 0.75
-            computeMaxSize();
-            referenceQueue = new ReferenceQueue<K>();
-        } else {
-            throw new IllegalArgumentException();
+        if (capacity < 0) {
+            throw new IllegalArgumentException("capacity < 0: " + capacity);
         }
+        elementCount = 0;
+        elementData = newEntryArray(capacity == 0 ? 1 : capacity);
+        loadFactor = 7500; // Default load factor of 0.75
+        computeMaxSize();
+        referenceQueue = new ReferenceQueue<K>();
     }
 
     /**
@@ -222,15 +221,17 @@
      *             or equal to zero.
      */
     public WeakHashMap(int capacity, float loadFactor) {
-        if (capacity >= 0 && loadFactor > 0) {
-            elementCount = 0;
-            elementData = newEntryArray(capacity == 0 ? 1 : capacity);
-            this.loadFactor = (int) (loadFactor * 10000);
-            computeMaxSize();
-            referenceQueue = new ReferenceQueue<K>();
-        } else {
-            throw new IllegalArgumentException();
+        if (capacity < 0) {
+            throw new IllegalArgumentException("capacity < 0: " + capacity);
         }
+        if (loadFactor <= 0) {
+            throw new IllegalArgumentException("loadFactor <= 0: " + loadFactor);
+        }
+        elementCount = 0;
+        elementData = newEntryArray(capacity == 0 ? 1 : capacity);
+        this.loadFactor = (int) (loadFactor * 10000);
+        computeMaxSize();
+        referenceQueue = new ReferenceQueue<K>();
     }
 
     /**
diff --git a/luni/src/main/java/java/util/regex/Matcher.java b/luni/src/main/java/java/util/regex/Matcher.java
index ce2dfe7..6ac32eb 100644
--- a/luni/src/main/java/java/util/regex/Matcher.java
+++ b/luni/src/main/java/java/util/regex/Matcher.java
@@ -194,7 +194,7 @@
      */
     private Matcher reset(CharSequence input, int start, int end) {
         if (input == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("input == null");
         }
 
         if (start < 0 || end < 0 || start > input.length() || end > input.length() || start > end) {
@@ -224,7 +224,7 @@
      */
     public Matcher usePattern(Pattern pattern) {
         if (pattern == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("pattern == null");
         }
 
         this.pattern = pattern;
diff --git a/luni/src/main/java/java/util/zip/Deflater.java b/luni/src/main/java/java/util/zip/Deflater.java
index 044b976..13f53c1 100644
--- a/luni/src/main/java/java/util/zip/Deflater.java
+++ b/luni/src/main/java/java/util/zip/Deflater.java
@@ -185,7 +185,7 @@
      */
     public Deflater(int level, boolean noHeader) {
         if (level < DEFAULT_COMPRESSION || level > BEST_COMPRESSION) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Bad level: " + level);
         }
         compressLevel = level;
         streamHandle = createStream(compressLevel, strategy, noHeader);
diff --git a/luni/src/main/java/java/util/zip/DeflaterInputStream.java b/luni/src/main/java/java/util/zip/DeflaterInputStream.java
index 805ce17..d854fec 100644
--- a/luni/src/main/java/java/util/zip/DeflaterInputStream.java
+++ b/luni/src/main/java/java/util/zip/DeflaterInputStream.java
@@ -78,7 +78,7 @@
             throw new NullPointerException("deflater == null");
         }
         if (bufferSize <= 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("bufferSize <= 0: " + bufferSize);
         }
         this.def = deflater;
         this.buf = new byte[bufferSize];
diff --git a/luni/src/main/java/java/util/zip/DeflaterOutputStream.java b/luni/src/main/java/java/util/zip/DeflaterOutputStream.java
index d336e72..448f61c 100644
--- a/luni/src/main/java/java/util/zip/DeflaterOutputStream.java
+++ b/luni/src/main/java/java/util/zip/DeflaterOutputStream.java
@@ -86,11 +86,11 @@
      * @param def
      *            is the specific {@code Deflater} that will be used to compress
      *            data.
-     * @param bsize
+     * @param bufferSize
      *            is the size to be used for the internal buffer.
      */
-    public DeflaterOutputStream(OutputStream os, Deflater def, int bsize) {
-        this(os, def, bsize, false);
+    public DeflaterOutputStream(OutputStream os, Deflater def, int bufferSize) {
+        this(os, def, bufferSize, false);
     }
 
     /**
@@ -113,19 +113,19 @@
      * @hide
      * @since 1.7
      */
-    public DeflaterOutputStream(OutputStream os, Deflater def, int bsize, boolean syncFlush) {
+    public DeflaterOutputStream(OutputStream os, Deflater def, int bufferSize, boolean syncFlush) {
         super(os);
         if (os == null) {
             throw new NullPointerException("os == null");
         } else if (def == null) {
             throw new NullPointerException("def == null");
         }
-        if (bsize <= 0) {
-            throw new IllegalArgumentException();
+        if (bufferSize <= 0) {
+            throw new IllegalArgumentException("bufferSize <= 0: " + bufferSize);
         }
         this.def = def;
         this.syncFlush = syncFlush;
-        buf = new byte[bsize];
+        buf = new byte[bufferSize];
     }
 
     /**
diff --git a/luni/src/main/java/java/util/zip/InflaterInputStream.java b/luni/src/main/java/java/util/zip/InflaterInputStream.java
index 6081037..397637e 100644
--- a/luni/src/main/java/java/util/zip/InflaterInputStream.java
+++ b/luni/src/main/java/java/util/zip/InflaterInputStream.java
@@ -98,24 +98,24 @@
      *            the {@code InputStream} to read data from.
      * @param inflater
      *            the specific {@code Inflater} for decompressing data.
-     * @param bsize
+     * @param bufferSize
      *            the size to be used for the internal buffer.
      */
-    public InflaterInputStream(InputStream is, Inflater inflater, int bsize) {
+    public InflaterInputStream(InputStream is, Inflater inflater, int bufferSize) {
         super(is);
         if (is == null) {
             throw new NullPointerException("is == null");
         } else if (inflater == null) {
             throw new NullPointerException("inflater == null");
         }
-        if (bsize <= 0) {
-            throw new IllegalArgumentException();
+        if (bufferSize <= 0) {
+            throw new IllegalArgumentException("bufferSize <= 0: " + bufferSize);
         }
         this.inf = inflater;
         if (is instanceof ZipFile.RAFStream) {
-            nativeEndBufSize = bsize;
+            nativeEndBufSize = bufferSize;
         } else {
-            buf = new byte[bsize];
+            buf = new byte[bufferSize];
         }
     }
 
diff --git a/luni/src/main/java/java/util/zip/InflaterOutputStream.java b/luni/src/main/java/java/util/zip/InflaterOutputStream.java
index 9a699a8..ca8a9508 100644
--- a/luni/src/main/java/java/util/zip/InflaterOutputStream.java
+++ b/luni/src/main/java/java/util/zip/InflaterOutputStream.java
@@ -76,7 +76,7 @@
             throw new NullPointerException("inf == null");
         }
         if (bufferSize <= 0) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("bufferSize <= 0: " + bufferSize);
         }
         this.inf = inf;
         this.buf = new byte[bufferSize];
diff --git a/luni/src/main/java/java/util/zip/ZipEntry.java b/luni/src/main/java/java/util/zip/ZipEntry.java
index e2bfc8d..3e58727 100644
--- a/luni/src/main/java/java/util/zip/ZipEntry.java
+++ b/luni/src/main/java/java/util/zip/ZipEntry.java
@@ -183,11 +183,10 @@
      *            the comment for this entry.
      */
     public void setComment(String comment) {
-        if (comment == null || comment.length() <= 0xFFFF) {
-            this.comment = comment;
-        } else {
-            throw new IllegalArgumentException();
+        if (comment != null && comment.length() > 0xffff) {
+            throw new IllegalArgumentException("Comment too long: " + comment.length());
         }
+        this.comment = comment;
     }
 
     /**
@@ -225,11 +224,10 @@
      *             when the length of data is greater than 0xFFFF bytes.
      */
     public void setExtra(byte[] data) {
-        if (data == null || data.length <= 0xFFFF) {
-            extra = data;
-        } else {
-            throw new IllegalArgumentException();
+        if (data != null && data.length > 0xffff) {
+            throw new IllegalArgumentException("Extra data too long: " + data.length);
         }
+        extra = data;
     }
 
     /**
diff --git a/luni/src/main/java/java/util/zip/ZipFile.java b/luni/src/main/java/java/util/zip/ZipFile.java
index 6ecd489..20bdf42 100644
--- a/luni/src/main/java/java/util/zip/ZipFile.java
+++ b/luni/src/main/java/java/util/zip/ZipFile.java
@@ -118,7 +118,7 @@
     public ZipFile(File file, int mode) throws IOException {
         fileName = file.getPath();
         if (mode != OPEN_READ && mode != (OPEN_READ | OPEN_DELETE)) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Bad mode: " + mode);
         }
 
         if ((mode & OPEN_DELETE) != 0) {
diff --git a/luni/src/main/java/java/util/zip/ZipOutputStream.java b/luni/src/main/java/java/util/zip/ZipOutputStream.java
index 47db8f6..77a993b 100644
--- a/luni/src/main/java/java/util/zip/ZipOutputStream.java
+++ b/luni/src/main/java/java/util/zip/ZipOutputStream.java
@@ -367,7 +367,7 @@
      */
     public void setLevel(int level) {
         if (level < Deflater.DEFAULT_COMPRESSION || level > Deflater.BEST_COMPRESSION) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Bad level: " + level);
         }
         compressLevel = level;
     }
@@ -382,7 +382,7 @@
      */
     public void setMethod(int method) {
         if (method != STORED && method != DEFLATED) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Bad method: " + method);
         }
         compressMethod = method;
     }
diff --git a/luni/src/main/java/libcore/icu/NativeDecimalFormat.java b/luni/src/main/java/libcore/icu/NativeDecimalFormat.java
index f6b5214..565da2e 100644
--- a/luni/src/main/java/libcore/icu/NativeDecimalFormat.java
+++ b/luni/src/main/java/libcore/icu/NativeDecimalFormat.java
@@ -280,8 +280,11 @@
     }
 
     public AttributedCharacterIterator formatToCharacterIterator(Object object) {
+        if (object == null) {
+            throw new NullPointerException("object == null");
+        }
         if (!(object instanceof Number)) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("object not a Number: " + object.getClass());
         }
         Number number = (Number) object;
         FieldPositionIterator fpIter = new FieldPositionIterator();
diff --git a/luni/src/main/java/libcore/net/http/HttpURLConnectionImpl.java b/luni/src/main/java/libcore/net/http/HttpURLConnectionImpl.java
index 260a9ad..9507745 100644
--- a/luni/src/main/java/libcore/net/http/HttpURLConnectionImpl.java
+++ b/luni/src/main/java/libcore/net/http/HttpURLConnectionImpl.java
@@ -406,7 +406,7 @@
     final boolean processAuthHeader(int responseCode, ResponseHeaders response,
             RawHeaders successorRequestHeaders) throws IOException {
         if (responseCode != HTTP_PROXY_AUTH && responseCode != HTTP_UNAUTHORIZED) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("Bad response code: " + responseCode);
         }
 
         // keep asking for username/password until authorized
diff --git a/luni/src/main/java/org/apache/harmony/security/asn1/ObjectIdentifier.java b/luni/src/main/java/org/apache/harmony/security/asn1/ObjectIdentifier.java
index 24140e5..eb1e3e3 100644
--- a/luni/src/main/java/org/apache/harmony/security/asn1/ObjectIdentifier.java
+++ b/luni/src/main/java/org/apache/harmony/security/asn1/ObjectIdentifier.java
@@ -190,7 +190,7 @@
             if (! shouldThrow) {
                 return null;
             }
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("str == null");
         }
 
         int length = str.length();
diff --git a/luni/src/test/java/tests/api/java/util/SimpleTimeZoneTest.java b/luni/src/test/java/tests/api/java/util/SimpleTimeZoneTest.java
index 618cbe4..eeb5b30 100644
--- a/luni/src/test/java/tests/api/java/util/SimpleTimeZoneTest.java
+++ b/luni/src/test/java/tests/api/java/util/SimpleTimeZoneTest.java
@@ -442,8 +442,18 @@
         st.setStartRule(0, 1, 1, 1);
         st.setEndRule(11, 1, 1, 1);
         st.setDSTSavings(1);
-        assertEquals("Daylight savings amount not set", 1, st.getDSTSavings());
-    }
+        assertEquals(1, st.getDSTSavings());
+        try {
+            st.setDSTSavings(0);
+            fail();
+        } catch (IllegalArgumentException expected) {
+        }
+        try {
+            st.setDSTSavings(-1);
+            fail();
+        } catch (IllegalArgumentException expected) {
+        }
+      }
 
     /**
      * java.util.SimpleTimeZone#setEndRule(int, int, int)
diff --git a/xml/src/main/java/org/kxml2/io/KXmlParser.java b/xml/src/main/java/org/kxml2/io/KXmlParser.java
index 2be8d36..80fd8ca 100644
--- a/xml/src/main/java/org/kxml2/io/KXmlParser.java
+++ b/xml/src/main/java/org/kxml2/io/KXmlParser.java
@@ -1612,7 +1612,7 @@
         boolean detectCharset = (charset == null);
 
         if (is == null) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("is == null");
         }
 
         try {
diff --git a/xml/src/main/java/org/kxml2/io/KXmlSerializer.java b/xml/src/main/java/org/kxml2/io/KXmlSerializer.java
index d1965d6..8fa2756 100644
--- a/xml/src/main/java/org/kxml2/io/KXmlSerializer.java
+++ b/xml/src/main/java/org/kxml2/io/KXmlSerializer.java
@@ -327,7 +327,7 @@
     public void setOutput(OutputStream os, String encoding)
         throws IOException {
         if (os == null)
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("os == null");
         setOutput(
             encoding == null
                 ? new OutputStreamWriter(os)