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

Question

Are there any open-source libraries that all programmers should know about? I'm thinking something general, a sort of extension to the standard java.util that contains basic functions that are useful for all kinds of application.

Answer 1

• Apache Commons

• Log4j

• Google collections

Answer 2

The Google Collections API is pretty handy if you use lots of, well, Collections...

Answer 3

It might be worth saying that the first thing to do is get to know the libraries in the newer versions of Java. A lot of ideas have worked their way back into java - java.util.concurrent, java.nio, and javax.xml

Answer 4

Apache's Jakarta Commons.

Answer 5

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 6

JXL for Excel workbook creation/edition. I work in a bank and the multipurpose report tool for diary work is Excel. Whatever appliction we do must import/export from/to Excel. The only fail it's that it has memory problems with large workbooks and formating it's a little obscure

Answer 7

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 8

Take a look at jmate project. It contains really helpful methods for strings, collections and IO operations (for now).

Look some examples here.

Answer 9

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 10

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

Answer 11

Google Collections migrated to great Guava Libraries . It contains some common utilities, string matcher, splitter, joiner, IO utils etc.