"A significant enhancement to the Java SE hashing-based Map implementations in planned for inclusion in Java SE 7u6. All of the hashing based Map implementations: HashMap, Hashtable, LinkedHashMap, WeakHashMap and ConcurrentHashMap will now use an enhanced hashing algorithm for string keys when the capacity of the hash table has ever grown beyond 512 entries. The enhanced hashing implementation uses the murmur3 hashing algorithm along with random hash seeds and index masks. These enhancements mitigate cases where colliding String hash values could result in a performance bottleneck."
Wonder how much stuff this is going to break...should be interesting :-)
(via +Jesse Wilson