MegaMap is a Java implementation of a map (or hashtable) that can store an unbounded amount of data, limited only by the amount of disk space available. Objects stored in the map are persisted to disk. Good performance is achieved by an in-memory cache. The MegaMap can, for all practical reasons, be thought of as a map implementation with unlimited storage space.
Netlib is a collection of mission-critical software components for linear algebra systems (i.e. working with vectors or matrices). Netlib libraries are written in C, Fortran or optimised assembly code. A Java translation has been provided by the F2J project but it does not take advantage of optimised system libraries.
fastutil extends the Java™ Collections Framework by providing type-specific maps, sets, lists and queues with a small memory footprint and fast access and insertion; it also includes a fast I/O API for binary and text files. It is free software distributed under the GNU Lesser General Public License.