JMockit Coverage is a code coverage tool with several metrics (line, path, data) capable of generating HTML reports. It is designed with ease of use in mind, avoiding the need for complex configuration.

jWeb1T is an open source Java tool for efficiently searching n-gram data in the Web 1T 5-gram corpus format. It is based on a binary search algorithm that finds the n-grams and returns their frequency counts in logarithmic time.

A suite of classification clustering algorithm implementations for Java. A number of partitional, hierarchical and density-based algorithms including DBSCAN, k-Means, k-Medoids, MeanShift, Affinity Propagation, HDBSCAN and more.

Code examples from Princeton's "Algorithms" textbook, 4th Edition.