http://fastutil.di.unimi.it/: fastutil extends the Java Collections Framework by providing type-specific maps, sets, lists and priority queues with a small memory footprint and fast access and insertion; provides also big (64-bit) arrays, sets and lists, sorting algorithms, and fast, practical I/O classes for binary and text files.
  • Sebastiano Vigna 
Static classes and methods used by all implementations and some non-type-specific classes that do not belong to objects. 
/**
 * Static classes and methods used by all implementations and some non-type-specific classes that do
 * not belong to {@link it.unimi.dsi.fastutil.objects}.
 */
package it.unimi.dsi.fastutil;