Primitive Collections for Java (PCJ) is a set of collection classes for primitive data types in Java. The goal is to provide an efficient alternative to the Java Collections Framework (JCF) when using primitive data types, such as int, boolean, or double. Some of its main features are:
PCJ provides symmetrical interface hierarchy for each of the primitive Java data types: boolean, char, byte, short, int, long, float, and double. Each hierarchy includes interfaces for general collections, sets, lists, and maps. To increase the learning rate and make adaptions easier to implement, each hierarchy resembles the interfaces of JCF as close as possible.