What is API in Java and Its Difference

API in Java

API stands for Application Programming Interface, and it is a set of programming instructions that allows two applications to communicate with each other. The API can be a software library or set of functions, classes, and data structures for building computer programs. Java, being one of the most popular programming languages, offers a robust framework for building and using APIs. This article delves into the realm of API in Java, exploring their types, facilitation in development, differences, and the advantages they bring to the table.

What Is An API In Java?

In Java, APIs are implemented in the form of Java packages, which contain classes, interfaces, and sub-packages that define various methods and fields used by different applications to communicate with each other. The API in Java is the set of classes, functions, and tools that make up the core of the Java programming language. It includes everything from basic data types like integers and floating-point numbers to more advanced concepts like networking, graphics, and user input. The Java language has an extensive set of APIs that can be used by developers to create their own custom libraries and applications.

Types Of API In Java

There are several types of API in Java, each with its own purpose. The following is a list of the most common types of API:

1. Public Java APIs

Public Java APIs are those that are available to the outside world, but they can be used by a private developer. These APIs are part of the standard Java libraries and are accessible to all developers. Examples of public Java APIs include the Java Standard Library, which includes packages like java.util, java.io, and java.lang, providing fundamental functionalities for data manipulation, I/O operations, and basic language features.

2. Private Or Internal Java API

Private or internal Java API is only meant for internal use by a specific organization or group of developers. These APIs are used within the Java platform itself and are not documented for external developers. They are subject to change without notice, and using them in your code is discouraged. However, some developers may attempt to access them for specific purposes, but it’s generally not recommended.

3. Partner Java APIs

Partner Java APIs are developed in conjunction with partners who have access to the source code and can modify it as per their needs. These APIs are designed to extend the functionality of Java and may include libraries for specific purposes, such as database access, graphical user interfaces, or web services. This is usually done as part of a contractual obligation between two parties (such as Oracle Corporation and IBM).

4. Composite Java APIs

Composite Java APIs consist of multiple other composite APIs; this means that you can create your own composite API using several other composites within it or simply add extra features onto existing composites without having any knowledge about how they work internally! They can be useful when dealing with intricate tasks that require interaction with various components of the Java ecosystem.

5. Web Java API

Web Java APIs are specialized APIs used for building web applications and services. These APIs facilitate communication between web clients (e.g., browsers) and web servers, allowing the exchange of data in various formats such as JSON or XML. Prominent web Java APIs include the Java Servlet API and the JavaServer Pages (JSP) API, both of which are integral to building web applications in Java.

Facilitation Of API In Java Development

Now that we know what kind of APIs Java has to offer, let’s explore how these APIs make it possible for developers to build applications.

1. Code Reusibility

The first and the most important advantage of using APIs is code reusability. When you develop an application, you can use some of the existing libraries in order to save your time and effort by just implementing them in your project. For example, say that there is already a library available for image processing, and if you want to create a new application where images must be edited before uploading, then all you have to do is just include this library in your project and use its methods rather than writing those codes again from scratch.

2. Encapsulation and Abstraction

Encapsulation and Abstraction are two other major advantages of using APIs because they allow us to access only required data while hiding other details from users, which helps us keep our system secure as well as maintainable over time without introducing bugs into it due to lack of knowledge about internal implementation details (for example an API could provide data about user’s address but not his email id).

3. Interoperability

Another advantage of using an API in Java is interoperability. Let’s say you are building a web application, then you might want to access data from some other systems such as FileMaker and Microsoft SQL Server, but these two don’t support any kind of API for integration. In this case, using an API would be the best solution because we could use its methods to access data from these databases without having any knowledge about their internal implementation details. It is particularly valuable in enterprise-level applications where multiple systems need to work together seamlessly.

Differences Between API in Java

In order to gain a deeper understanding of API in Java, we need to explore the key differences between various types of APIs and their implementations.

1. Core Java API vs. Third-party APIs

The Core API in Java, also known as the Java Standard Library, is the foundation of Java programming. It includes packages like java.util, java.io, and java.lang, providing core functionalities such as data manipulation, I/O operations, and essential language features. Third-party APIs, on the other hand, are developed by external organizations and vendors to extend Java’s capabilities. These APIs cater to specific domains, such as database access, GUI development, or web services.

2. OpenJDK API vs Oracle JDK API

OpenJDK (Java Development Kit) is an open-source implementation of the Java Platform, Standard Edition (Java SE). It comes with a set of APIs that are open and available for everyone to use. Oracle JDK, on the other hand, is a commercial version of Java, and some of its APIs may have additional features or enhancements that are not present in OpenJDK. Developers need to be aware of these differences when choosing between the two.

3. Java SE API vs. Java EE API

Java SE (Standard Edition) and Java EE (Enterprise Edition) are two different flavors of Java, tailored for different application domains. The Java SE API focuses on general-purpose programming and includes core libraries for desktop and standalone applications. In contrast, the EE API in Java is designed for building enterprise-level applications and provides APIs for web services, enterprise beans, and database connectivity. Choosing the right API depends on the nature of your project and its requirements.

Advantages Of API In Java

There are several advantages of using API in Java.

1. Modularity and Component-Based Development

API in Java is highly modular and component-based, which is one of the reasons why it’s so popular. It allows you to divide your application into several modules or components that can be developed separately. The code in each module can be reused by other parts of the application without any problems.

2. Ecosystem Integration

API in Java has a thriving ecosystem. There are many tools and frameworks that can be used to develop applications with API. You’ll find plenty of libraries and plugins for the most common tasks, such as web services integration or database access. There are many new tools and frameworks available in Java, which means that you’ll always find something useful when you need it.

3. Cross-Platform Compatibility

Java is a cross-platform language, which means that you can run the same code on many different platforms. You can develop applications for Linux, Windows, or Mac operating systems, and they will still work on any of them. This also means that you don’t have to learn a new language each time you want to build something new—you can use Java for every project!

4. Performance Optimization

Java is a fast language, and it’s easy to optimize your code. The JVM allows you to achieve maximum performance without having to worry about memory leaks or CPU overloads, which means that your system will run much smoother than if it were written in another language. Java applications offer better response times, reduced latency, and more efficient memory usage than many other languages.

5. Legacy Code Integration

Java can be used to integrate with legacy code, which is a great way to get started with the language. You can use Java’s powerful libraries to access legacy code and make it easier to maintain while keeping your original architecture intact. Java also allows you to leverage existing APIs and frameworks in order to reuse code from other projects.


In the end, we can say that API is a way to access the functionality of Java classes. Java offers a diverse range of APIs, from public and partner APIs to web and composite APIs, each catering to specific needs and use cases. The use of Java APIs brings numerous benefits, including code reusability, encapsulation, abstraction, interoperability, and more. By leveraging these advantages, developers can streamline their development processes, build scalable applications, and ensure that their code remains efficient and maintainable.

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