How Java Works: JDK, JRE, JVM & JDK Installation

Introduction: How Does Java Work?

Many beginners ask:
“I write Java code, but how does it actually run?”

Java works using a special environment that makes programs run safely on different computers.
This environment is made of three main components:

  • JDK

  • JRE

  • JVM

Understanding these will make Java easy and logical, not confusing.

How Java Works – Step by Step

Java works in three simple steps:

  1. You write Java code

  2. Java converts it into bytecode

  3. Java runs the program on any system

Let’s understand the tools involved.

What Is JVM (Java Virtual Machine)?

Simple Definition

The JVM is a virtual machine that runs Java programs.

 

What Does JVM Do?

  • Reads Java bytecode

  • Converts it into machine code

  • Executes the program

Why JVM Is Important

  • Makes Java platform-independent

  • Ensures security and memory management

JVM is the reason Java works everywhere

What Is JRE (Java Runtime Environment)?

Simple Definition

The JRE provides everything needed to run Java programs.

 

JRE Includes

  • JVM

  • Core Java libraries

When Do You Need JRE?

  • When you only want to run Java applications

  • Not used for writing Java code

JRE = Environment to run Java programs

What Is JDK (Java Development Kit)?

Simple Definition

The JDK is used to develop and write Java programs.

 

JDK Includes

  • JRE

  • Java compiler

  • Development tools

When Do You Need JDK?

  • When learning Java

  • When writing and compiling Java code

Every Java learner needs JDK

Relationship Between JDK, JRE, and JVM

Think of them like this:

  • JVM → Runs Java programs

  • JRE → Provides the runtime environment

  • JDK → Provides tools to create Java programs

Hierarchy

JDK → JRE → JVM

Real-Life Analogy

Think of Java like cooking:

  • Java Code → Recipe

  • JDK → Kitchen with cooking tools

  • JRE → Cooking environment

  • JVM → Chef who cooks the food

Installing Java JDK (Step-by-Step for Beginners)

To start learning Java, you must install the Java Development Kit (JDK).

Step 1: Download Java JDK

  1. Go to the official Oracle Java website

  2. Download the latest Java JDK

  3. Choose the version for your operating system:

    • Windows

    • macOS

    • Linux

Step 2: Install Java JDK

On Windows

  1. Double-click the downloaded installer

  2. Click Next → Install

  3. Wait for installation to complete

On macOS

  1. Open the downloaded .dmg file

  2. Follow on-screen instructions

On Linux

  1. Use package manager or terminal commands

  2. Install OpenJDK or Oracle JDK

Step 3: Verify Java Installation

Open Command Prompt / Terminal and type:

java -version

If Java is installed correctly, you will see the Java version displayed.

Step 4: Verify Java Compiler

Type:

javac -version

This confirms that JDK is properly installed.

Frequently Asked Questions (FAQs)

Q1. Do I need JDK or JRE to learn Java?

You need JDK to write and practice Java programs.

 

Q2. Is JVM installed automatically with JDK?

Yes. JDK includes JRE, and JRE includes JVM.

 

Q3. Can Java work without JVM?

No. JVM is required to run Java programs.

 

Q4. Which Java version should beginners install?

The latest LTS (Long-Term Support) version is recommended.

 

Q5. Is Java free to install?

Yes. OpenJDK is free and widely used.