java-intro.md

Introduction to Java

Java is a high-level, object-oriented programming language developed by Sun Microsystems in 1995. It is mostly used for building desktop applications, web applications, Android apps, and enterprise systems.

Key Features

• Platform Independent: Code compiles into bytecode that runs on any JVM. "Write Once, Run Anywhere."
• Object-Oriented Programming (OOP): Java supports OOP concepts to create modular and reusable code.
• Statically Typed: Variables must be declared with a type. Compiler catches errors early.
• Robust and Secure: Java ensures reliability and security through strong memory management and exception handling.
• Multithreading and Concurrency: Java allows concurrent execution of multiple tasks for efficiency.

Hello World Program in Java

public class HelloWorld {  // Declares a public class named HelloWorld. File must be HelloWorld.java
    public static void main(String[] args) {  // Main method - entry point of the program
        System.out.println("Hello World!");  // Prints "Hello World!" to the console
    }  // End of main method
}  // End of class

Output

Hello World!

How does Java code run?

• Write code in a file like HelloWorld.java.
• Java Compiler "javac" compiles it into bytecode "HelloWorld.class".
• JVM (Java Virtual Machine) reads the .class file and interprets the bytecode.
• JVM converts bytecode to machine-readable code (binary 0s and 1s) and then executes the program.