Java Hello World Program (original) (raw)

Last Updated : 12 May, 2026

Java Hello World Program is the first and simplest program that beginners learn. It demonstrates the basic structure of a Java program and how to display output on the console using Java syntax.

• It helps understand the basic structure of a Java program (class, main method)
• It is the starting point for learning Java programming

Prerequisites

• Download install JDK.
• Download install intelliJ

Implementation of Java Hello World

The below-given program is the most simple program of Java printing "Hello World" to the screen. Let us try to understand every bit of code step by step.

Java `

public class HelloWorld {

// Your program begins with a call to main()

public static void main(String[] args)
{
    // Prints "Hello, World" to the terminal window.
    
    System.out.println("Hello, World");
}

}

`

Understanding the Java Hello World Program

**1. Class Definition

Every Java program must have at least one class. Here, the class is defined using the **class keyword:

public class HelloWorld {
// Statements go here
}

**Note:

If the class is public, the filename must match the class name HelloWorld.java

**2. main Method

In the Java programming language, every application must contain a main method as it is the entry point of the application:

public static void main(String[] args)

• **public: Allows JVM to access the method from anywhere.
• **static: Method can run without creating an object.
• **void: It doesn’t return any value.
• **String[] args: Accepts command-line arguments.

**3. System.out.println()

This prints output to the console.

System.out.println("Hello, World");

• **System: Built-in class from java.lang package.
• **out: Static member (PrintStream object) of System.
• **println(): Method that prints to console and moves to the next line.

Steps to Implement a Java Program

Java is a platform-independent language that follows a two-step execution process:

• Compilation (source code -> bytecode)
• Execution (bytecode -> machine code via JVM)

1. Compilation in Java

Java source code (.java files) is compiled by the Java Compiler (javac) into Bytecode, stored in .class files. This bytecode is platform-independent and ready to run on any system with a JVM.

• **Internally, compilation involves:
• **Parsing: Converts code into syntax trees (AST).
• **Entering: Populates symbol tables.
• **Annotation Processing: Handles annotations.
• **Attribution: Performs type checking and name resolution.
• **Flow **Analysis: Checks for variable use and reachability.
• **Desugaring: Removes syntactic shortcuts.
• **Generation: Produces .class files.

2. Execution via JVM

The .class files are executed by the Java Virtual Machine (JVM), which includes the following stages:

Class Loader

Loads the main class and other dependencies into memory.

• **Primordial Loader: Default system loader.
• **Non-primordial Loader: Custom loaders for advanced control.

Class r = loadClass(String className, boolean resolveIt);

**Bytecode Verifier

Checks that the loaded bytecode is safe to execute. It ensures:

• Variables are initialized
• Method signatures are correct
• Private access rules aren’t violated
• No stack overflows

**Just-In-Time (JIT) Compiler

Converts bytecode into native machine code at runtime for faster execution.

Just-In-Time (JIT) Compiler

Java Compilation and Execution Example

Java `

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

`

Steps to Run

**1. Create File: Save the file as HelloWorld.java.
**2. Open Terminal: Navigate to the folder containing the file.
**3. Compile:

javac HelloWorld.java

**4. Run:

java HelloWorld

**Output

Hello, World

**1. In Windows

Shell

**2. In Linux

Shell

**Note: If you get ClassNotFoundException, ensure the .class file is in the correct directory or check your CLASSPATH.