Module 1: Java Fundamentals & Environment Setup

What is Java?

Java is a high-level, object-oriented programming language developed by Sun Microsystems (now Oracle) in 1995. It's designed to be platform-independent, meaning Java programs can run on any device that has a Java Virtual Machine (JVM).

Java vs C: Key Differences

Java Virtual Machine (JVM)

The JVM is what makes Java "Write Once, Run Anywhere":

Java 24 New Features

Required Software

IDE Options

Java File Structure

Every Java program must follow this structure:

// File: HelloWorld.java
public class HelloWorld {
    public static void main(String[] args) {
        // Your code here
        System.out.println("Hello, World!");
    }
}

Key Components Explained

public class HelloWorld

public static void main(String[] args)

{
    // Statements go here
}

Naming Conventions

String Concatenation

String concatenation is the process of joining (combining) multiple strings together to create a single string. In Java, you use the + operator to concatenate strings.

// Simple string concatenation
String firstName = "John";
String lastName = "Doe";
String fullName = firstName + " " + lastName;  // "John Doe"

// Concatenating strings with numbers
int age = 25;
String message = "I am " + age + " years old";  // "I am 25 years old"

// Multiple concatenations
String greeting = "Hello, " + firstName + "! You are " + age + " years old.";
// Result: "Hello, John! You are 25 years old."
System.out.println(greeting);

int a = 5;
int b = 3;

String result1 = a + b + " is the sum";      // "8 is the sum" (5+3=8, then "8"+" is the sum")
String result2 = "The sum is " + a + b;      // "The sum is 53" ("The sum is " + "5" + "3")
String result3 = "The sum is " + (a + b);    // "The sum is 8" (parentheses force addition first)

Simple Hello World Example

Let's start with the most basic Java program - the traditional "Hello World":

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

Compilation and Execution

# Compile the Java file
javac FirstProgram.java

# Run the compiled program
java FirstProgram

IDE Features