Top Libraries and APIs Java Developer Should Learn To Improve His Programming Skill

Java is the most popular programming language in both web & mobile application development. It is also rated as one of the top programming languages. One of the key reasons behind its immense success is the presence of a feature-rich and vast Core library. It is advisable to use the default Standard Java library for building powerful, secure & innovative applications; with additional libraries which are needed. Java has been serving developers & researchers for the last two decades with innovative and useful libraries.

Here in this blog post, we are discussing top Java libraries from all domains. Whether you build an application for a college project or gaming application, all these libraries mentioned are useful. Such libraries are highly popular and when an enterprise a hire Java developer they make optimum use of them for application development.

1. Apache Commons

Apache Commons in Java development helps to extend the functionality of Core libraries. When utility class is written in a project, the chances of an already existing Apache Commons library are high. It includes more than 40 modular libraries including Collections, Classes, Math, Database, and Caching.

Main Features:

• Java Classes
• Logging Utilities 
• JDBC Helper 
• I/O Utilities 
• Framework extension
• Statistics components

2. Google Guava

Google Guava is a top-grade Java library. It was developed & released by Google in its initial days. Currently, it is an open-source project where several engineers apart from Google contributed. It comprises essential utilities, collections, concurrency utilities, graph libraries, hashing, and string manipulation. Google Guava offers better software design when compared to Apache Commons.

Main features:

• Hashing 
• I/O utilities
• String utilities
• Caching
• Concurrency Utilities

3. Jackson

Data is very important for both web or mobile applications. It is required to process various formats of data, and which can be saved in different formats, or you have to transfer it in multiple formats.

JSON is basically a de-facto data exchange format in the latest software development. Other common data formats include Avro, YAML, CSV, XML, BSON, CBR.

Jackson offers data-binding and annotations. It is simple to convert POJO to data or generate POJO from data with the support of Jackson annotations. If you work with data format, Jackson is a must-have library. It is highly modular offering basic functionality and different extension modules.

Main features:

• JSON schema 
• Standard and collection data types
• Specific modules for different Data types Avro, CBOR, CSV
• Kotlin native types
• Support third-party data types
• Core modules for the stream, annotations, and supports JSON data format

4. JAXB

XML is another established data format offering stricter data validation, storage, and transportation facilities. Until Java 8, the Java Standard library offers XML support, comprising data binding. Since Java 9, the XML processing functionalities are not part of the Standard Java library and moved to a different library, JAXB.

JAXB offers everything to work with XML in Java including a standard and efficient way of mapping XML and Java code. It additionally comprises annotation-based data binding.

Main features:

• W3C XML Schema features
• Annotation-based Java-to-XML data binding
• Validation

5. SLF4J

Logging is an integrated and important phase of Software application Development. Proper logging will ensure the smooth working of the software and ensure no error occurs. Java Standard library provides basic Logging in java.Util.Logging. Additional logging libraries include Log4j, Log4j 2, Logback, offering advanced logging facilities. SLF4J offers abstraction or facade for different logging libraries. It permits the users to change logging libraries during deployment.

At first, it may seem counterproductive to use the extra facade library SLF4J for logging. But with the help of SLF4J, it will give additional flexibility to change the concrete logging library smoothly if necessary. It is always recommended to use a preferred logging framework like a pluggable logger to the SLF4J.

Main features:

• Provides abstraction of the logging framework.
• Feature to change logging framework during runtime.
• Supports all major logging frameworks.
• Offers a library with essential tools and features.
• Event logger to record events.

6. Log4j 2

There are several outstanding logging libraries present in Java including java.Util.logging, Log4j, Log4j 2, Logback. But seeing the features it is revealed that Log4j 2 and Logback are the two most powerful logging libraries. For an enterprise project, the logging library performance is crucial, particularly asynchronous logging, peak throughput, and latency. 

Main features:

• Advanced filtering.
• Enhanced performance through Asynchronous logging.
• Plugin architecture.
• Cloud support.
• Separates API from implementation.

7. Mockito 

Testing is an essential phase of the Application Development process. Developers want to test a single Class but it relies on other heavyweight classes or external functionalities. A result-oriented way to write the test case is via mocking. Just mock the behavior of other additional Service calls and only work on the Class to test.

Mockito is the most successfully used mocking library of Java. Mockito is perfect for testing a small project or a huge Enterprise Java project with a very simple, & clean API.

Main features:

• Lean and clean API
• Offers a simplified stubbing model
• Supports Partial mocking 
• Annotation-based mock injection.
• Behavior-driven development syntax 

8. AssertJ

AssertJ is the second library related to TDD. Testing helps to check whether the test result matches the expected result. JUnit offers a built-in assertion mechanism in class org.JUnit.Assert. It provides different static methods for test verification. But professional developers consider those couple of methods insufficient.

There are two mighty assertion libraries within the Java landscape: Hamcrest Matchers and AssertJ assertions. The AssertJ is highly modular, has a fluent API, and offers the desired functionalities in its Core module with advanced functionalities.

Main features:

• Fluent assertion API for code readability.
• Rich set of assertions with helpful error messages.
• Key module for Standard Java Library.
• Modules to offer assertions in reputed Java libraries.
• Module to offer assertions for SQL databases.

9. Apache HTTPComponents

HTTP is the most used and prevalent Application-Layer protocol. Java library does not offer many features to handle HTTP. Luckily, Apache HTTPComponents offers a toolset of Java components focused on HTTP. Apache HTTPComponents is highly modular, providing a Core module to build custom Client/Server HTTP services. It also offers value-added modules for the latest functionalities including an Asynchronous HTTP Client.

Main features:

• Low-level HTTP Transport Components for Client/Server services.
• Offers blocking and non-blocking I/O models.
• Synchronous HTTP Client for client-side authentication, state management, as well as connection management.
• Asynchronous HTTP Client to serve a large array of concurrent connections.

So these are some of the most popular Java libraries for web & mobile application development used by developers. 

Wrapping Up

These are some of the useful libraries every Java developer must integrate as per the development requirement. The Java sphere is vast, and you will find hundreds of libraries to perform diverse things. If you want to build anything in Java, you will find a library on how to do just that. As always, search engines are your best friend to avail useful Java libraries, but another option is to take a look at the Maven central repository to find desired libraries for your development task.