Java Fundamentals

IB Syllabus: B2.1 — Programming fundamentals

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Overview

Before writing programs with loops and arrays, you need to understand the building blocks: variables, data types, operators, and how to get input from the user.

Topic	What you learn	Syllabus
Variables & Data Types	Declaring variables, primitives, Strings, operators, Scanner	B2.1.1
String Methods	Manipulating text with built-in methods	B2.1.2
Exception Handling	try/catch/finally for runtime errors	B2.1.3
Debugging	Print statements, trace tables, breakpoints	B2.1.4

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How Java Works

Java is both compiled and interpreted — a two-step process:

Your Code (.java)  →  Compiler (javac)  →  Bytecode (.class)  →  JVM  →  Output

The JVM (Java Virtual Machine) reads bytecode and translates it for whichever platform it runs on — this is why Java is “write once, run anywhere.”

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Structure of a Java Program

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

Key rules:

• The class name must match the filename exactly (HelloWorld.java)
• Java is case-sensitive — main is not Main
• Every statement ends with a semicolon ;
• Execution always begins in the main method

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Table of contents

• Variables & Data Types
• String Methods
• Exception Handling
• Debugging Strategies