What is the most useful multi-purpose open-source library for java? [closed]

Answer 1

lambdaj is a thread safe library of static methods that provides an internal DSL to manipulate collections in a pseudo-functional and statically typed way without explicitly iterating on them. It eliminates the burden to write (often poorly readable) loops while iterating over collections.

Answer 2

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Answer 3

Functional Java offers first-class function values, immutable lists/arrays, lazy/infinite streams, tuple types, either types, optional values (type-safe alternative to null). Works well in conjunction with Google Collections or the java.util collections.

It also provides handy concurrency abstractions like parallel strategies, parallel list/array functors, actor concurrency, and composable light-weight processes.

Answer 4

The Spring framework is surprisingly general purpose. I started by just using it as a configuration management tool, but then realized how helpful dependency injection is when doing test-driven development. Then I slowly discovered many useful modules hidden in the corners of Spring.

Answer 5

Apache's Jakarta Commons.

Answer 6

Here is a good start. http://java-sources.org/