Difference Between JDK, JRE, and JVM

Have you ever wondered about the backbone of Java programming? The JDK (Java Development Kit) equips developers with tools for Java application development, the JRE (Java Runtime Environment) enables the execution of those applications with necessary libraries and the JVM (Java Virtual Machine), and the JVM itself executes Java bytecode, making Java applications platform-independent. Let's understand more!

Java is a popular programming language for developing various applications, from desktop software to web applications and mobile apps. When working with Java, you may come across the terms JDK, JRE, and JVM, all of which are important components of the Java ecosystem.

JDK, JRE, and JVM are three distinct components used to run Java applications, but they each serve a different purpose. Understanding the differences between these components is important for Java developers and anyone else who works with Java applications. This blog post will explore the differences between JDK, JRE, and JVM and explain why each component is important in Java development.

Table of Content

• Difference between JVM, JRE, and JDK
• What is JVM in Java?
• What is JRE in Java?
• What is JDK in Java?

Let’s begin with understanding JVM first.

Difference between JVM, JRE, and JDK

Below is a table differentiating between JVM, JRE and JDK.

What is JVM?

Java Virtual Machine (JVM) is an abstract machine responsible for compiling and executing Java code. It is a part of the Java Runtime Environment (JRE), which calls the main function of a program.

• JVM facilitates a platform-independent way of executing Java source code. Its basis on WORA (Write Once Run Anywhere).
• It has a class loader, runtime data area, execution engine, and libraries.
• JVM comes with JIT(Just-in-Time) compiler that converts Java source code into machine code.

First, the Java compiler compiles a Java file into a Java .class file. Then, the .class file works as an input into the JVM, which loads and executes the class file.

Features of JVM

• It converts byte code to the machine language.
• JVM provides basic Java functions like memory management, security, garbage collection, etc.
• Runs the program by utilizing JRE’s libraries and files.
• JVM is an integral part of JRE.
• It can execute the Java program line by line. Therefore, it is also known as an interpreter.
• The main functions of JVM include loading, linking, initializing, and compiling the program.

Note: JVM can’t be installed alone. As JVM is a part of JRE, you need to install JRE. JVM comes within it.

What is JRE?

JRE software includes JVM and class libraries to run Java programs independently. Although it can execute the code. Yet, JRE comes bundled with Java Development Kit (JDK) to provide a complete application development experience.

• The JRE includes class libraries along with JVM and its supporting files. Note: It does not include separate tools, such as a debugger for Java development.

• JRE comprises significant package classes such as util, math, AWT, lang, and various runtime libraries.

JRE = JVM + Class Libraries (For Running the Java Applications).

Features of JRE

• JRE consists of a set of tools to help the JVM run. In addition, it includes a few deployment tools such as Java Plug-in and Java Web Start.
• A User can efficiently run a Java code with JRE only. However, JRE doesn’t allow writing the program.
• JRE appends various integration libraries like the JDBC (Java Database Connectivity), JNDI (Java Naming and Directory Interface), RMI (Remote Method Invocation), etc.
• Along with JVM, it consists of a virtual machine client for Java HotSpot.

What is JDK?

Java Development Kit (JDK) is a complete software environment for building applications and applets using the Java programming language. It is platform-dependent. Therefore, it has different OS platform versions for Windows, Linux, Mac, etc. It allows reading, writing, and executing the Java program.

• Includes various tools required for writing Java programs.
• It includes an applet viewer, Java application launcher, debugger, compiler, etc.
• JDK also consists of JRE for executing Java programs.
• The Java application launcher helps in opening a JRE. Then, it loads the necessary details and executes the program’s main method.

JDK = Development Tools + JRE (Java Runtime Environment)

Features of JDK

• JDK provides an environment for developing and executing the Java source code.
• It includes all the functionalities of JRE and JVM.
• JDK helps developers handle the exceptions using multiple extensions in a single catch block.
• It has various other development tools like the debugger, compiler, etc.
• It is platform-dependent. Moreover, users can easily install JDK on Operating systems like Unix, Mac, Windows, etc.

Also, read: Top Java Project Ideas for Beginners to Try

Conclusion

Java is one of the most popularly used programming languages worldwide. Java Development Kit (JDK) plays a vital role in Gaming, GUI, Web, and Mobile Application Development. 

I hope you enjoyed reading the above article and learned something new. Share your comments and queries related to Java in the link below and embrace your learning experience with us.

Practice: Top 161 Java Interview Questions and Answers