High performance collections for Java

If you are on look out fpr a high performance collection libray , then here is one for you GNU Trove .The Trove library provides high speed regular and primitive collections for Java

Few excerpts from Trove website here

The GNU Trove library has two objectives:

• Provide "free" (as in "free speech" and "free beer"), fast, lightweight implementations of the java.util Collections API. These implementations are designed to be pluggable replacements for their JDK equivalents.
• Provide primitive collections with similar APIs to the above. This gap in the JDK is often addressed by using the "wrapper" classes (java.lang.Integer, java.lang.Float, etc.) with Object-based collections. For most applications, however, collections which store primitives directly will require less space and yield significant performance gains

Some Info:) : It looks Trove's TLongIntHashMap uses only 27 bytes per entry , where as original java impl uses around 100 bytes per entry ,stated here