This document discusses the top 10 Java libraries. It provides details on the most popular libraries including the Java Standard Library, Apache Commons, Google Guava, Mockito, JUnit, Jackson libraries, JAXB, HttpClient, Log4j 2, and DBCP. These libraries expand Java's functionality, aid in testing, facilitate data handling and formatting, enable HTTP requests and XML processing, improve logging, and help manage database connections.

1. In this article, we will talk about the Top 10 Libraries of Java. Java’s
prominence in the industry stands still due to its vast significant
features. Most of the business applications that exist today have Java as
their backbone. A java library contains many modules that come under
an identical theme. It expands the functionality of the Java code and
lets the developer reduce complexities in the code. Apart from the
core library that is possessed, there are other extensive Java libraries
available in the market. This article will list the most remarkable Java
libraries and their functionalities.

2. 1. Java Standard Library:
The Java Standard library is the most popular library as it comes with the
programming language itself. Many people fail to notice the importance and
robustness of the standard library present in Java. Some of the standard libraries
include:
• The java.util class consists of all the data structures and collections in it.
• java.lang is the most basic library that lets us use many functionalities like various
data types in the program code. Thus, if you want to add the String, Int, Double,
or any other datatype, you must include the java.lang library.

3. 2. Apache Commons:
Apache Commons is a general-purpose library or in other words, an
open-source project that consists of reusable Java components.
Some of the most popular ones are:
• Commons BSF
• Commons CSV
• Commons Crypto
• Commons IO
• Commons Numbers
• Commons Text

4. 3. Google Guava:
The Google Guava library is an alternative to Apache Commons. It is
also a General-purpose library that contains various core Java
libraries. It was initially developed by Google, and later many
engineers contributed to its growth. Guava has unswervingly been
one of the most popular Java libraries. It is categorized into three
heads such as:
• Google Collections Library
• Basic utilities – Implements common methods and functions.
• Miscellaneous utilities – provides features for productivity

5. 4. Mockito:
When it comes to Unit/integration testing, the concept of mocking is
a much more familiar one. In mocking, we can easily test a single
class that depends on heavyweight classes or external functionalities
such as Database operations or I/O operations. This is done by
mocking the behavior of the other external Service calls and
focusing only on the class that we need to test.
The developers can test double objects or dummy objects for
behavior-driven and test-driven behavior. Irrespective of the size of
the project, a popular mocking library is Mockito. With simple API, it
provides an effective result during Unit/integration testing.

6. 5. JUnit:
Another popular testing framework is JUnit. As the name
suggests, the developers can easily run unit tests using this
framework. Any bug or error must be eradicated from the unit
level, therefore being proficient in unit testing is crucial.
6. Jackson libraries:
In the process of software development, it is common that we would
come across data in various formats. The data must be loaded or
saved in various formats or transferring of data from one format to
another must take place. JSON makes this task easier to accomplish
as it acts as de facto. There are other data formats like CSV, BSON,
CBR, Avro, XML, YAML, Protobuf, etc.

7. 7. JAXB:
The full form of JAXB is Java Architecture for XML binding. It is an
XML parsing library that lets us bind XML schemas and Java
presentations. As the Java Standard Library in Java 9 does not
support XML functionalities, this led to the adoption of separate
libraries like JAXB to serve the purpose.
8. HttpClient:
The Java Development Kit or the JDK does not support HTTP
requests. Therefore, to implement HTTP connections, the java.net
package is preferred. The other third-party libraries like Apache
HttpClient and HttpCore are not simple to use.

8. 9. Log4j 2:
Various logging libraries in Java like java.util.logging, Log4j, Log4j 2,
and Logback are available. The last two libraries like Log4j 2 and
Logback are comparatively powerful. In the case of large projects,
the logging libraries may perform as expected.
10. DBCP:
The full form of DBCP is Database Connection Pool Library. In most
cases, the software is developed in many languages or platforms.
Rare is software that is limited to one language or platform. In the
former scenario, we need to integrate the databases in Java
applications. This is where the role of the Database Connection pool
libraries is vital.

9. Developing large projects entirely from scratch without
implementing the libraries would seem like a reinventing
wheel in the modern era. Therefore, it is essential to know
the libraries that can minimize the workload. I hope this
article gave you a proper insight into what a library is and a
brief idea about the popular Java libraries.