/Java Programming

Java Programming

Comprehensive guided learning module covering syntax, object-oriented principles, exception handling, and the collections framework.

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Chapter Overview

Java is a popular, class-based, object-oriented programming language designed by James Gosling at Sun Microsystems in 1995. It runs on the Write Once, Run Anywhere principle using the Java Virtual Machine (JVM).

Structure of a Java program

Every Java program is written inside a class. The filename must match the public class name (e.g., Main.java). Execution starts from the main method: public static void main(String[] args).

Compilation & JVM

Source .java → Compiler javac → Bytecode .class → JVM java. The JVM interprets/JIT-compiles bytecode into native machine instructions.

Comments

// Single-line comment /* Multi-line comment */ `/** Javadoc comment used to generate API docs */

Identifiers & Keywords

Names of classes, methods, and variables are identifiers. Keywords like public, class, static, void are reserved by Java.

System.out.println()

Standard output function. System is a class, out is a static print stream, and println is the method that prints text followed by a newline.

Strict Rules

Java is case-sensitive, statements must end with semicolons, and code blocks are enclosed in curly braces {}.

Example Code

public class Main {
    public static void main(String[] args) {
        // Print hello message to console
        System.out.println("Hello, Java!");
    }
}