Judy is a c library that implements a dynamic array. empty judy arrays are declared with null pointers. a judy array consumes memory only when populated yet can grow to take advantage of all available memory. judy's key benefits are: scalability, performance, memory efficiency, and ease of use. judy arrays are designed to grow without tuning into the peta-element range, scaling near o(log-base-256).

judy arrays are accessed with insert, retrieve, and delete calls for number or string indexes. configuration and tuning are not required -- in fact not possible. judy offers sorting, counting, and neighbor/empty searching. indexes can be sequential, clustered, periodic, or random -- it doesn't matter to the algorithm. judy arrays can be arranged hierarchically to handle any bit patterns -- large indexes, sets of keys, etc.

judy is often an improvement over common data structures such as: arrays, sparse arrays, hash tables, b-trees, binary trees, linear lists, skiplists, other sort and search algorithms, and counting functions.