Top 12 Java Libraries You Should Know of in 2021

The choice of a good programming language becomes absolutely crucial when writing code for various back-end development projects in fields like Big Data, Machine Learning, Web Development, Android Development,etc.JAVA has emerged as one of the most powerful tools which have come to the aid of thousands of developers for over 25 years now. JAVA has been able to maintain its position in the top three most popular languages for a very long time because of the platform which it provides. The JAVA platform consists of more than just a programming language. It also provides a large number of code libraries, which are ready-made code components that are used extensively by developers. So, whether it be the field of Algorithms and Data Structures, or be it development, JAVA can prove to be of humongous use to all the budding coders of modern times. Whether you need to crack a coding interview (find more details here) or develop a project, JAVA is definitely one of the languages you can opt for.

Code libraries sit at the heart of the JAVA platform and form an extremely important part of the open-source ecosystem. Libraries implement the idea of code reusability and prevent developers from reinventing the wheel every time the code. Not only does this save everyone’s time, but also provides a standard for a community of people to come together and support the development of the platform.

TOP JAVA LIBRARIES WHICH YOU SHOULD KNOW OF:-

While there are thousands of JAVA libraries out there, there are some JAVA libraries that we think everyone should know of in 2021:-

1) JAVA STANDARD LIBRARIES:-

The JAVA Standard Libraries provide a tonne of functionalities that can be used by the developers in various capacities. Given below is the description of a few of them:-

• java.lang — Provides classes that are fundamental to the design of the JAVA programming language. java.lang is always implicitly imported.
• java.net — Provides classes for implementing network applications.
• java.util — Contains the Collections framework and provides event model, legacy collection classes, date and time facilities, and miscellaneous utility classes like String Tokenizer, etc
• java.math — Provides classes for performing arbitrary-precision integer arithmetic (using BigInteger) and arbitrary-precision decimal arithmetic (using BigDecimal).
• java.io — Provides for system input and output using data streams, file system, and serialization.

2) Log4j 2:-

One of the most essential parts of Production-grade Software Development is Logging. The proper usage of logging can help developers understand the working of their software and also help them detect the root cause of errors that have occurred, especially in the production system. There are a lot of excellent logging libraries provided by JAVA, for example:-

• java.util.logging (provided in the JAVA Standard Library)
• Log4j
• Log4j 2
• Logback

Among these, Log4j 2 is a very powerful logging library because of the following features:-

• It uses Asynchronous Logging due to which performance is improved.
• It has Advanced filtering, cloud support, and plugin architecture.
• In Log4j 2, the API is separated from the implementation.

3) SLF4J:-

While the logging libraries like Log4j, Logback,etc provide concrete implementation, SLF4J provides an abstraction, that is, a facade for these logging libraries. Although it might sound a bit counter-productive to use an additional abstraction for the logging libraries, the fact that SLF4J allows the developers to change the concrete logging libraries effortlessly if needed makes it one of the most important libraries of JAVA. Given below are a few features of SLF4J:-

• The logging framework can be changed during runtime.
• It provides a library, namely “slf4j-ext.jar”, which has helpful tools for software developers.
• It also provides an event logger for recording events.

4) APACHE COMMONS:-

Another extremely powerful and diverse library of JAVA is the Apache Commons Library. It is an Apache project focussed on all aspects of the reusable components of JAVA. Apache Commons comprises more than 40+ modular libraries like Database, Collections, Math, Classes, etc and therefore, it is widely used in the industry. The Apache Commons consists of three parts:-

• The Commons Proper — A repository of reusable JAVA components.
• The Commons Dormant — A repository of components that are currently inactive.
• The Commons Sandbox — A workspace for Java component development.

Apache Commons has the following features which make it highly popular:-

• Commons Math — Consists of Mathematics and Statistics components.
• Input/Output(Commons IO) and Logging(Commons Logging) Utilities.
• Commons CLI — It provides an API for parsing command-line argument

5) GOOGLE GUAVA:-

Guava is one of the top-grade general-purpose libraries of JAVA developed by Google. It is modular and contains many independent libraries. Given below is a list of utilities and libraries which Guava consists of:-

• String utilities
• Concurrency Utilities
• JAVA Collections Framework extensions
• I/O utilities
• Caching and Hashing

6) JACKSON:-

Software Development involves the processing of data in various formats like JSON, XML, YAML,
Avro, etc.One of the most commonly used suites of data processing libraries in JAVA is Jackson. It consists of Jackson JSON, which is the de facto streaming JSON parser and generator library. There is also support for additional data formats like Avro, XML, YAML, etc, and data types like Joda, Guava, etc in Jackson. Jackson is a must-have tool in a developer’s toolset because of the following characteristics:-

• It has core modules for streaming,data-binding, and annotations.
• It supports standard and collection data types.
• It supports third-party data types like Lombok, Yandex Bolts, MongoDB, etc.

7) GOOGLE GSON:-

Gson is yet another JAVA library that has been developed by Google and can be used to convert JAVA objects into their JSON (JavaScript Object Notation) representation and vice versa. Gson can work with arbitrary JAVA objects including pre-existing objects that we do not have source-code of. Listed below are a few goals of Gson which makes it better than the other open-source projects that convert JAVA objects to JSON:-

• Gson provides the simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa.
• Gson has extensive support of JAVA Generics.
• It allows pre-existing unmodifiable objects to be converted to and from JSON.
• Gson allows custom representations for objects.
• It supports arbitrarily complex objects (with deep inheritance hierarchies and extensive use of generic types).

8) JAXB:-

Apart from JSON, another prevalent data format that offers stricter validation, storage, and transportation of data is XML. The JAVA Standard Library had XML support until JAVA 8. From JAVA 9, the support for XML is discontinued in the JAVA Standard Library and has been moved to a separate library known as JAXB (JAVA Architecture for XML Bindings).JAXB provides an API and tools that automate the mapping between JAVA objects and XML documents.JAXB users have to write less code themselves and do not have to be experts in XML because JAXB enables them to perform the following operations:-

• Unmarshal XML content into JAVA representation.
• Access and update the JAVA representation.
• Marshal the JAVA representation of the XML content into XML content.

9) MOCKITO:-

One of the most crucial parts of Software Development is Testing(Unit Testing, Integration Testing, etc).In some scenarios, developers want to test a particular class (SUT) that is dependent on other classes for some functionalities, for example — DataBase operations, Input/Output operations, etc. Mocking is a way to write the Unit or Integration tests in such scenarios. Mockito is one fantastic library that can be used for mocking the behavior of external service calls and focus on the class which we want to test. Mockito provides the following features:-

• A simplified stubbing model.
• Spy for partial mocking.
• Spy injection(annotation-based mocking)
• Lean and clean API
• BDDMockito for behavior-driven development syntax

10) JUNIT:-

JUnit is another widely used library that allows developers to write code for Unit Testing. It provides functionalities for conducting repeatable tests on our code.JUnit 5 is the latest version of JUnit.Some of JUnit’s main features are as follows:-

JUnit provides JAVA 8 features and can be used for both Unit and Integration testing.
A lot of major IDEs like Eclipse, IntelliJIDEA, NetBeans, and many more, provide JUnit integrations, and therefore, developers can both run and write unit tests from those IDEs.

11) AssertJ:-

The main purpose of Test Driven Development (or TDD) is to verify that the software that has been developed works perfectly and that the test results match the expected results.JUnit has a built-in assertion mechanism in its class “org.junit.Assert”, which offers a couple of static methods for test verification. However, there is definitely a need for some advanced functionalities as well. This is where a rich library of the JAVA landscape like AssertJ comes into the picture. The main features of AssertJ which make it extremely useful are:-

• Better code readability due to fluent assertion API.
• Core modules for JAVA Standard Library.
• Modules to provide assertions for SQL databases and other popular JAVA libraries like Guava, Neo4j, and many more.

12) HIBERNATE:-

Software Developers have to deal with Data Stores(SQL and NoSQL) on a daily basis. A way of dealing with them is to use low-level APIs like JDBC for SQL, etc. However it is not portable and therefore, to deal with data stores, an abstraction layer is introduced between the data stores and the application which the developers develop. This abstraction layer, also called ORM(Object Relational Mapping), maps the JAVA classes to the DataBase tables or collections. One of the most famous ORM libraries is Hibernate as it provides the following features:-

• Domain Model Persistence for relational databases (ORM) and NoSQL data stores(OGM).
• Full-text search for domain models.
• Annotation-based validations for domain models.

CONCLUSION:-

That is all about some of the essential JAVA libraries a developer should know of in 2021. It is pretty evident by now that the usage of these excellent libraries can not only help in the entire Software Development process but also help save the time of the developers as they do not have to reinvent the wheel again when they code. JAVA developers can definitely benefit from these libraries if they use them in their day-to-day work. Also, there is a huge community of developers standing behind these JAVA libraries who are ready to help other JAVA developers perform their tasks well. Want to Become a Full Stack Developer? Learn How