jmemcached is a fast network available cache daemon. It is protocol-compatible with memcached, but written in Java and suitable for applications with portability concerns, where Java is the preferred solution, or for using the memcached protocol in embedded applications with alternate storage engines. Existing clients for memcache work unmodified. It can run as a standalone daemon or be embedded inside an existing Java application.
K-tree provides a scalable approach to clustering by combining the B+-tree and k-means algorithms. Clustering can be used to solve problems in signal processing, machine learning, and other contexts. It has recently been used to solve document clustering problems on the Wikipedia collection.
Crash Dummy is a Java Web application to help IT professionals set up Java application server environments. It has several features to help make this easier, including simulating failures and diagnostics. Crash Dummy is particularly helpful for setting up complex clustered environments and monitoring infrastructure.
ClodHopper is a Java library for high-performance clustering of numerical data. It contains clustering implementations such as K-Means, K-Means++, X-Means, G-Means, Fuzzy C-Means, Jarvis-Patrick, and various forms of hierarchical clustering. ClodHopper's clustering implementations take advantage of the host system's concurrent processing ability to speed clustering. The data structures are also very lean to conserve memory usage. ClodHopper is very extensible. If you are developing a new clustering algorithm, you may save yourself an enormous amount of work by extending a ClodHopper base class.