---
title: "Introduction to Java Programming"
description: Java evolution, features, JVM/JRE/JDK, basic syntax, and compilation workflow.
---
## Evolution of Java

Java was developed by James Gosling at Sun Microsystems in 1995. It was designed to be platform-independent, following the principle of "Write Once, Run Anywhere" (WORA).

## Java Features

Java is known for being:

- **Simple** — Clean syntax derived from C/C++ with automatic memory management.
- **Object-Oriented** — Everything revolves around classes and objects.
- **Platform-Independent** — Bytecode runs on any platform with a JVM.
- **Robust** — Strong type checking, exception handling, and garbage collection.
- **Secure** — No explicit pointers, bytecode verification, and a security manager.
- **Multithreaded** — Built-in support for concurrent programming.
- **High-Performance** — Just-In-Time (JIT) compilation.
- **Distributed** — Support for networking via RMI and EJB.
- **Dynamic** — Runtime class loading and reflection.
- **Architecture-Neutral** — Fixed-size primitive types across platforms.

## Java Workflow: JVM, JRE, JDK

- **JDK (Java Development Kit)** — Full development environment including compiler (`javac`), debugger, and tools.
- **JRE (Java Runtime Environment)** — Runtime libraries and the JVM needed to run Java programs.
- **JVM (Java Virtual Machine)** — Executes Java bytecode on any platform.

## Basic Syntax

A Java program consists of **classes**, **methods**, and **statements**:

- The `main` method is the entry point: `public static void main(String[] args)`.
- Comments can be single-line (`//`), multi-line (`/* */`), or Javadoc (`/** */`).
- Identifiers must start with a letter, underscore, or dollar sign.

## Compilation and Execution

```bash
javac HelloWorld.java   # Compile to bytecode
java HelloWorld         # Run with JVM
```

## Example

```java
// HelloWorld.java
// This is a simple Java program that prints "Hello, World!" to the console.

public class HelloWorld {
	// The main method is the entry point of any Java program.
	public static void main(String[] args) {
		// Prints Hello, World! to the console.
		System.out.println("Hello, World!");
	}
}
```

> Full source: [`examples/01-introduction/HelloWorld.java`](https://github.com/University-Of-Sri-Jayewardenepura/Java/blob/main/examples/01-introduction/HelloWorld.java)

## User Input

Java provides the `Scanner` class for reading user input:

```java
import java.util.Scanner;

Scanner sc = new Scanner(System.in);
String name = sc.nextLine();
int age = sc.nextInt();
```