1. JSON Libraries


JSON parsing libraries in the modern era of information technology, JSON plays a very important role as it is a medium to transfer information from the client to the server. The traditional XML’s parsing which was platform-dependent has been replaced with JSON as it is platform-independent.
Currently, Java Development Kit does not yet have a JSON library but many other useful third-party libraries are available which can help you parse as well as create JSON messages just like Gson or Jackson.

                                            http://jnnctechnologies.com/

2. Unit testing libraries


The most important part of the development lifecycle is Unit Testing. This separates an average programmer from a good programmer. Most of the programmers have trouble writing unit test cases as they mostly are unaware of the popular testing libraries of JAVA which can benefit them in writing error-free code before they pass it for QA. Some of the most widely used libraries are Mockito, PowerMock, JUnit, etc which allow programmers to test their code with desired inputs and see the results.