Introduction to Java | Programming Basics

JDK, JVM, and JRE in Java

When you start programming in Java, you'll often encounter terms like JDK, JVM, and JRE. These are essential components of the Java programming environment. Understanding the differences between them will help you as you set up your development environment and run Java programs.

What is JDK?

The JDK (Java Development Kit) is a software development kit used to develop Java applications. It includes:

• JVM: The Java Virtual Machine to run Java applications.
• JRE: The Java Runtime Environment to run Java applications.
• Development Tools: Tools like the Java compiler (javac) and the debugger.

The JDK is the complete package for developing Java programs. If you're developing Java applications, you'll need to install the JDK.

What is JVM?

The JVM (Java Virtual Machine) is a virtual machine that runs Java bytecode. It is platform-independent, meaning Java applications can run on any machine that has the JVM installed, regardless of the underlying hardware and operating system.

• The JVM interprets the compiled bytecode of Java applications and executes it.
• It handles memory management, garbage collection, and exception handling.
• The JVM is crucial for Java's "Write Once, Run Anywhere" (WORA) philosophy because it abstracts the platform-specific details from the developer.

What is JRE?

The JRE (Java Runtime Environment) is a package that includes everything required to run Java applications, except for the development tools like the compiler. It consists of:

• JVM: The virtual machine that executes Java bytecode.
• Libraries: A set of libraries and other files needed to run Java applications.
• The JRE is necessary if you only want to run Java programs but not develop them.

Differences Between JDK, JVM, and JRE

Code Example: JDK, JVM, and JRE in Action

Here’s a simple example of a Java program that runs on the JVM. To develop and run this program, you'll need the JDK to compile it and the JVM to run it.

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

Output

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