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

[{'answer_id': 64229, 'author': 'Chris Broadfoot', 'author_id': 3947, 'author_profile': 'https://Stackoverflow.com/users/3947', 'pm_score': 5, 'selected': True, 'text': '<ul>\n<li><p>Apache Commons</p></li>\n<li><p>Log4j</p></li>\n<li><p>Google collections</p></li>\n</ul>\n'}, {'answer_id': 64231, 'author': 'Mat Mannion', 'author_id': 6282, 'author_profile': 'https://Stackoverflow.com/users/6282', 'pm_score': 2, 'selected': False, 'text': '<p>The <a href="http://code.google.com/p/google-collections/" rel="nofollow noreferrer">Google Collections API</a> is pretty handy if you use lots of, well, Collections...</p>\n'}, {'answer_id': 64294, 'author': 'Nick Fortescue', 'author_id': 5346, 'author_profile': 'https://Stackoverflow.com/users/5346', 'pm_score': 2, 'selected': False, 'text': '<p>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 </p>\n'}, {'answer_id': 64295, 'author': 'Adrian', 'author_id': 7426, 'author_profile': 'https://Stackoverflow.com/users/7426', 'pm_score': 2, 'selected': False, 'text': '<p>Apache\'s <a href="http://commons.apache.org/" rel="nofollow noreferrer">Jakarta Commons</a>.</p>\n'}, {'answer_id': 64318, 'author': 'Don Kirkby', 'author_id': 4794, 'author_profile': 'https://Stackoverflow.com/users/4794', 'pm_score': 3, 'selected': False, 'text': '<p>The <a href="http://www.springframework.org/" rel="nofollow noreferrer">Spring framework</a> 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.</p>\n'}, {'answer_id': 64837, 'author': 'Telcontar', 'author_id': 518, 'author_profile': 'https://Stackoverflow.com/users/518', 'pm_score': 0, 'selected': False, 'text': '<p><a href="http://jexcelapi.sourceforge.net/" rel="nofollow noreferrer">JXL</a> 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</p>\n'}, {'answer_id': 66003, 'author': 'Apocalisp', 'author_id': 3434, 'author_profile': 'https://Stackoverflow.com/users/3434', 'pm_score': 2, 'selected': False, 'text': '<p><a href="http://functionaljava.org" rel="nofollow noreferrer">Functional Java</a> 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.</p>\n\n<p>It also provides handy concurrency abstractions like parallel strategies, parallel list/array functors, actor concurrency, and composable light-weight processes.</p>\n'}, {'answer_id': 66427, 'author': 'Marcio Aguiar', 'author_id': 4213, 'author_profile': 'https://Stackoverflow.com/users/4213', 'pm_score': 0, 'selected': False, 'text': '<p>Take a look at <strong><a href="http://code.google.com/p/jmate/" rel="nofollow noreferrer">jmate</a></strong> project. It contains really helpful methods for strings, collections and IO operations (for now). </p>\n\n<p>Look some <a href="http://javaadami.blogspot.com/2008/08/whenever-scripting-language-wants-to.html" rel="nofollow noreferrer">examples here</a>.</p>\n'}, {'answer_id': 912941, 'author': 'Mario Fusco', 'author_id': 112779, 'author_profile': 'https://Stackoverflow.com/users/112779', 'pm_score': 2, 'selected': False, 'text': '<p>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. </p>\n'}, {'answer_id': 913028, 'author': 'Peter Lawrey', 'author_id': 57695, 'author_profile': 'https://Stackoverflow.com/users/57695', 'pm_score': 2, 'selected': False, 'text': '<p>Here is a good start. <a href="http://java-sources.org/" rel="nofollow noreferrer">http://java-sources.org/</a></p>\n'}, {'answer_id': 3707905, 'author': 'Piotr Gwiazda', 'author_id': 221951, 'author_profile': 'https://Stackoverflow.com/users/221951', 'pm_score': 2, 'selected': False, 'text': '<p>Google Collections migrated to great <a href="http://code.google.com/p/guava-libraries/" rel="nofollow noreferrer">Guava Libraries</a> . It contains some common utilities, string matcher, splitter, joiner, IO utils etc.</p>\n'}, {'answer_id': 23703968, 'author': 'Grzegorz Gajos', 'author_id': 397677, 'author_profile': 'https://Stackoverflow.com/users/397677', 'pm_score': 0, 'selected': False, 'text': '<p>Lately I was trying to find answer to this question. I made some data analysis for this, you can find results <a href="http://www.77dev.com/2014/05/java-trends-top-100-mostly-used.html" rel="nofollow">here</a> and <a href="http://www.77dev.com/2014/05/what-are-most-popular-java-libraries.html" rel="nofollow">here</a>.</p>\n'}]
['https://Stackoverflow.com/questions/64213', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/8330/']