10 Java Libraries Every Developer Should Know About

With so many Java libraries to choose from, it can be hard to know where to start. We’ve scoured the web to compile a list of 10 of the most popular Java libraries to give you a starting point.

Have we missed one you think deserves to be on the list? Let us know over on LinkedIn, and share your favorite Java libraries with the team.

Top 10 Java Libraries

1. Apache Commons
2. Guava
3. Jackson
4. JUnit
5. Java Standard Library
6. HTTP Libraries
7. Log4j2 (Logging Library)
8. Mockito
9. Gson
10. Lombok

1. Apache Commons

Apache Commons is an important Java library to be aware of because it’s a general-purpose library with a range of reusable Java components. Apache Commons is made up of three parts:

1. The Commons Proper
2. The Common Sandbox
3. The Commons Dormant

Apache Commons includes modules such as Commons Text, Commons IO, Commons CSV, and Commons Numbers.

2. Guava

Like the Apache Commons library, Google Guava is a general-purpose library initially developed by — surprise, surprise — Google. (Many engineers outside Google have since contributed to this open-source project).

Offering advanced features that go beyond Apache Commons, Guava’s main features include

• I/O utilities
• String utilities
• Hashing
• Caching
• The extension of the Java collection framework

3. Jackson

Perhaps one of the most used JSON parsing libraries, Jackson lets developers serialize and map Java objects to JSON (or vice versa). It’s a popular choice for developers due to its high performance, lightweight structure, and accuracy.

The Java library includes various tools and approaches for working with JSON, including data binding annotations on POJO classes, and additional data format modules.

Jackson supports different data types, including

• Standard collection datatypes
• Java 8 Module
• Hibernates
• & more

Jackson processes data encrypted in

• BSV
• XML
• CBOR
• BSON
• TOML
• & more

4. JUnit

Many consider JUnit an “essential” Java library because of its role in bug fixing. This popular unit testing library facilitates testing from unit to integration and, when combined with Selenium, can perform end-to-end testing as part of a single “mvn clean build” command.

Note: JUnit runs tests randomly without following a set sequence, so it’s important to create test cases that are independent of each other.

5. Java Standard Library

Java Standard Libraries are often unjustly overlooked and include robust and functional libraries such as

• Java.util
• Java.lang
• Java.math
• Java.net
• Java.io/Jave.nio

New developers take note - these libraries can form the cornerstone of building a solid programming base, so ignore them at your peril.

6. HTTP Libraries

HTTP libraries (including Google HTTP Client and Apache HttpComponents) facilitate making HTTP requests and handling responses in Java. Given that JDK doesn’t support HTTP, these libraries are essential for any developer needing to make requests.

7. Log4j2 (Logging Library)

Logging libraries are among the most common Java libraries because they’re required in every project. While JDK ships with its own logging library, many developers prefer alternatives, including Log4j2 or Log5j. These are similar in style, but Log5j uses Java’s variable arguments (varargs) feature, which Log4j does not.

8. Mockito

Mockito is another unit testing library similar to JUnit. When used during unit testing, this open-source mocking framework means you don’t have to spin up an entire environment for your testing. It enables developers to test double or dummy objects for behavior-driven and test-driven behavior.

Note: Mockito was voted the best mocking framework for Java on StackOverflow.

9. Gson

Gson converts Java objects to their JSON representation and vice versa, making this Java library perfect for applications that require straightforward JSON data handling. Although often discussed in conjunction with Jackson, Gson operates at the document level, while Jackson excels in streaming (de)serialization.

10. Lombok

Lombok is another popular Java library developers should know about. It can generate known patterns of code, allowing developers to reduce the boilerplate code in a project. This not only saves time during development but also increases the readability of source code and saves space.

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