The direct replacements match the API - but not all behaviors are covered by the API, and so they may not work for your program.
This module provides a lock-free alternate implementation of java.util.concurrent.ConcurrentHashMap with better scaling properties and generally lower costs to mutate the Map. It provides identical correctness properties as ConcurrentHashMap. All operations are non-blocking and multi-thread safe, including all update operations. It scales substatially better than the standard java.util.concurrent.ConcurrentHashMap for high update rates, even with a large concurrency factor. Scaling is linear up to 768 CPUs on a 768-CPU Azul box, even with 100% updates or 100% reads or any fraction in-between. Linear scaling up to all cpus has been observed on a 32-way Sun US2 box, 32-way Sun Niagra box, 8-way Intel box and a 4-way Power box.
If you want to drop-in the non-blocking versions of ConcurrentHashMap you'll need to alter your bootclasspath - these classes come directly from your JDK and so are found via the System loader before any class-path hacks can be done.
To replace the JDK implementation of ConcurrentHashMap with the better scaling version, add java_util_concurrent_chm-1.1.2.jar to your java launch line:
java -Xbootclasspath/p:java_util_concurrent_chm-1.1.2.jar my_app_goes_here
