Design patterns implemented in Java

RxJava – Reactive Extensions for the JVM – a library for composing asynchronous and event-based programs using observable sequences for the Java VM.

A programmer-oriented testing framework for Java — ⚠️ maintenance mode

Master repository for the JGraphT project

Implementation of various string similarity and distance algorithms: Levenshtein, Jaro-winkler, n-Gram, Q-Gram, Jaccard index, Longest Common Subsequence edit distance, cosine similarity ...

A Java library for technical analysis.

Google HTTP Client Library for Java

Hashids algorithm v1.0.0 implementation in Java

Use graphviz with pure java

Visual programming meets Haskell

The combined power of JUnit, Guice and Mockito. Plus it sounds like a cool martial art.

Jadler is a Java library for stubbing and mocking HTTP servers and resources in a declarative way.