Open source Java libraries

Top 10 Java libraries for saving time

Martin Patsov
Java libraries
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There are a lot of Java libraries out there. How can a busy developer separate the wheat from the chaff? In this article, Martin Patsov explains why he loves open source Java libraries and goes over his top 10 list.

To use, or not to use, that is the question:
Whether ’tis java library will save your soul
Or the hope will come to failure and destroy?
Many brave before you here have been,
So let me save the bother that you keep within.

While I am getting really poetic right here on my own, I know the struggle is real. There are lots of Java libraries out there and it’s hard to sort through them all. Personally, I’m a library evangelist. Here are a few reasons why I love them!

Libraries are an important part of the open source ecosystem. Open source libraries usually have great communities standing behind them. After all, it’s hard for a library to exist without a community putting in the effort to support and develop it.

Libraries keep us from having to reinvent the wheel every time we code. Reuse as much code as possible! Using libraries saves times, as does not implementing every single line of code by myself. Instead, I use that time to do things like spend time with family and friends.

Top 10

There are hundreds of thousands of libraries out there. I want to save you a lot of time in research and choosing the best ones, the most well documented ones, the most supported and up-to-date ones as well the ones that should save as much time as possible.

I want to point out that these recommendations are all my personal opinions. They are all open source and free for use.

1. Java standard libraries

Yep, that’s right, you heard me right. A lot of people underestimate or do not fully know the Java Standard libraries and do not know how to unleash its full power when programming or they don’t use it at all. Here is a brief description of some of the libraries:

  • java.lang is always implicitly being imported as it contains everything you basically cannot program without String, Double, Enum, Math, etc.
  • In java.util you can find all the collections and data structures available in Java
  • Next, we have for reading files, working with pipes, streams and similar.
  • Also we have java.nio, which actually is the alternative to and stands for non-blocking I/O. It allows intensive use of the input/output operations as you might guess.
  • java.math provides functionality for working with arbitrary-precision decimal (BigDecimal) and integer (BigInteger) values
  • is being used for working with sockets, creating connections or in short – creating networking applications
  • In Java we also have libraries for working with GUI : javax.swing (extension of the older java.awt)
  • We even can play music and create midi files with java.sound

You can find more about the Java Standard library here.

2. JHipster

JHipster is a development platform to generate, develop and deploy Spring Boot + Angular Web applications and Spring microservices.

Man, this one have saved me months of development . I could definitely say that this one is my personal favourite and that I keep a special place for it in my heart. It basically generates your whole application from your front-end to the back-end. The only thing you need to add is the business logic behind the architecture. The main and most important libraries, which are included in the generated project are:

You can find more about JHipster here.

3. Maven

Maven is a software project management and comprehension tool. Honestly, Maven is great. If you’ve never used Maven before, you’re missing out. Sometimes, I wonder how it was even possible to create enterprise applications prior to its creation.

Maven can manage all your project dependencies, configurations and build configurations and even documentation only by specifying them in a single pom.xml file.

You can find more about Maven here.

SEE MORE: Top 5 machine learning libraries for Java

4. Apache Commons

Apache Commons is actually a whole project focused on creating Java libraries.

Here is a short list of some of the best and most commonly used libraries:

  • Commons Math: The Apache Commons Mathematics Library – the name says it all: this library contains components allowing advanced mathematics and statistics operations and computations
  • Commons CLI – provides API for parsing command line arguments. Why will you even bother creating an application without the ability to pass parameters and control its behavior?!
  • Commons CSV – whatever you are developing, at some point you are going to face the necessity of using csv files. This include opening, reading, editing, saving and creating them. I suggest using the RFC 4180 format from the CSVFormat class and UTF-8 encoding when saving/creating files.
  • Commons IO – it is being used for easier execution of input/output operations. Checking at least the ReversedLinesFileReader is definitely worth it.

You can find more about Apache Commons here.

5. Guava

Guava is the Google Core Libraries for Java. It is a library for extending the basic Java collections functionalities

This is an utility I absolutely have to mention. Did you ever needed ordering for your collections? Did you ever need to compare the contents there? What about advanced sort and compare on multiple columns with multiple conditions? I present you one of my most favorite components in this library:

  • ComparisonChain is used for implementing advanced and complicated comparison sort for collections.

You can find more about Guava here.

6. google-gson

google-gson is helpful for converting Java Objects to JSON and vice versa.

This library is especially helpful when developing mobile applications and creating/using REST APIs as well as in any case you would need to convert a Java Object to its JSON representation and vice versa.

You can find more about google-gson here.

SEE MORE: Top 5 open-source tools for machine learning

7. Hibernate-ORM

Hibernate-ORM is an object relational mapper. It’s used for persisting of data in relational databases. It provides an easier and more abstract way of doing that for the developers. It uses JDBC in its implementation. Hibernate is also an implementation of the JPA specification.

You can find more about Hibernate ORM here.

8. Mockito 

Despite the name, Mockito is not an alcohol-free mixed drink but instead a mocking framework. Sorry to disappoint.

However, Mockito enables you to create mocks and write tests easier with simpler and cleaner code. Writing great tests has never been easier!

You can find more about Mockito here.

9. JUnit 

JUnit is a free Java framework for writing unit tests. It provides functionality for conducting repeatable tests on your code. You just need to be careful not to get obsessed with the numbers (% code coverage). Bigger code coverage does not always mean better and bug-less code.

You can find more about JUnit here.

10. Log4j and Slf4j

The two of these are both logging frameworks. Slf4j represents an abstraction for other logging frameworks (such as Log4j ). On the other hand, Log4j is just a simple logging framework.

You can find more about Log4j here and Slf4j here.


Martin Patsov

Martin Patsov is a Full Stack Developer at Dreamix, a bespoke software development company. He has experience in software development with Java, entrepreneurship, management of small teams and communication with clients. His drive is in sharing the knowledge, being the change in society he wants to see and transferring the sparkles he ignites to those around him.
You can find him on LinkedIn, Google+, and follow him on Twitter @Dreamix_Ltd.

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2 years ago

How about lombok..I have used it extensively and found it quiet useful