June 2012 - core-libs-dev

hg: jdk8/tl/jdk: 7173036: test/com/sun/jdi/ConnectedVMs.java does not run as expected
by weijun.wang＠oracle.com 04 Jun '12

04 Jun '12

Changeset: a5bb0343f135 Author: weijun Date: 2012-06-04 18:06 +0800 URL: http://hg.openjdk.java.net/jdk8/tl/jdk/rev/a5bb0343f135 7173036: test/com/sun/jdi/ConnectedVMs.java does not run as expected Reviewed-by: alanb ! test/com/sun/jdi/ConnectedVMs.java

1 0

[doc]Small modification on the WeakHashMap doc
by Charles Lee 04 Jun '12

04 Jun '12

Hi guys, In the Implementation notes of WeakHashMap[1], says: /One way to deal with this is to wrap values themselves within WeakReferences before inserting, as in: m.put(key, new WeakReference(value)), and then unwrapping upon each get./ However, it is not concise and a little misleading. Because the value in the WeakReference can be GC'd if there are no strong reference to it. This behaviour surprises some customers. How about add a statement like [2]: /However, as the use of WeakReference in this manner will not prevent value objects from being GC'd, this approach is only useful when entries in the map are not relied upon for keeping the underlying value objects "live"./ [1]: http://docs.oracle.com/javase/7/docs/api/java/util/WeakHashMap.html [2]: http://cr.openjdk.java.net/~littlee/7166055/webrev.00/ <http://cr.openjdk.java.net/%7Elittlee/7166055/webrev.00/> -- Yours Charles

3 9

hg: jdk8/tl/jdk: 7166055: Javadoc for WeakHashMap contains misleading advice
by littlee＠linux.vnet.ibm.com 04 Jun '12

04 Jun '12

Changeset: 237e27c7ddc3 Author: littlee Date: 2012-06-04 16:30 +0800 URL: http://hg.openjdk.java.net/jdk8/tl/jdk/rev/237e27c7ddc3 7166055: Javadoc for WeakHashMap contains misleading advice Reviewed-by: dholmes, mduigou ! src/share/classes/java/util/WeakHashMap.java

1 0

HashMap bug for large sizes
by Kasper Nielsen 02 Jun '12

02 Jun '12

Hi, I don't know if this has been discussed before. But I was looking at the HashMap implementation today and noticed that there are some issues with very large sized hashmaps with more then Integer.MAX_VALUE elements. 1. The Map contract says that "If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE." The current implementation will just wrap around and return negative numbers when you add elements (size++). 2. If the size of a HashMap has wrapped around and returns negative size you cannot deserialize it. Because of this loop in readObject for (int i=0; i<size; i++) { K key = (K) s.readObject(); V value = (V) s.readObject(); putForCreate(key, value); } If someone wants to play around with the size limits of HashMap I suggest taking the source code of HashMap and change the type of the size field from an int to a short, in which case you can test this with less the xx GB of heap. There are probably other map implementations in the JDK with the same issues. Cheers Kasper

4 6

hg: jdk8/tl/jdk: 7173432: Handle null key at HashMap resize
by mike.duigou＠oracle.com 01 Jun '12

01 Jun '12

Changeset: 7baa22e6a6b3 Author: mduigou Date: 2012-06-01 00:05 -0700 URL: http://hg.openjdk.java.net/jdk8/tl/jdk/rev/7baa22e6a6b3 7173432: Handle null key at HashMap resize Summary: If the key to be inserted into a HashMap is null and the table needs to be resized as part of the insertion then addEntry will try to recalculate the hash of a null key. This will fail with an NPE. Reviewed-by: darcy ! src/share/classes/java/util/HashMap.java + test/java/util/HashMap/NullKeyAtResize.java

1 0