This is a word-aligned compressed variant of the Java Bitset class. It provides both a 64-bit and a 32-bit RLE-like compression scheme. It can be used to implement bitmap indexes.

The goal of word-aligned compression is not to achieve the best compression, but rather to improve query processing time. Hence, JavaEWAH tries to save CPU cycles, maybe at the expense of storage. However, the EWAH scheme is always more efficient storage-wise than an uncompressed bitmap (as implemented in the BitSet class by Sun).