JDK, JRE, and JVM difference in Java

Introduction

JDK, JRE, and JVM are parts of Java that help run and create Java programs. Knowing their difference helps you understand how Java works.

When you want to write and compile Java programs.

When you want to run Java programs on your computer.

When you want to understand how Java executes your code.

When you need to set up your computer to develop Java applications.

When you want to troubleshoot Java program errors.

Syntax

Java

No code syntax applies here because these are tools and components, not code statements.

JDK stands for Java Development Kit.

JRE stands for Java Runtime Environment.

Examples

JDK includes everything in JRE plus tools to write and compile Java code.

Java

JDK = JRE + tools for development (like compiler)

JRE includes JVM and the libraries needed to run Java programs but not to develop them.

Java

JRE = JVM + libraries to run Java programs

JVM is the part that actually runs the Java program on your computer.

Java

JVM = Java Virtual Machine that runs Java bytecode

Sample Program

This simple Java program prints a message. To run it, you need JRE and JVM. To write and compile it, you need JDK.

Java

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

Important Notes

You need JDK to write and compile Java programs.

You need JRE to run Java programs.

JVM is inside JRE and runs the Java program.

Summary

JDK is for developing Java programs (write + compile + run).

JRE is for running Java programs only.

JVM is the engine that runs Java bytecode inside JRE.