Java Control Flow – if-else, switch & Loops Explained Introduction

In Week 1, we learned what Java is and wrote our first “Hello World” program.
In Week 2, we covered Java syntax, variables, and data types.

Now, in this article, it’s time to make our programs dynamic.
We’ll explore control flow statements in Java, which let us decide what a program should do under different conditions and repeat tasks efficiently.

By the end of this article, you’ll understand:

• if-else statements
• switch-case statements
• for, while, and do-while loops
• How to combine conditions for practical programs

What Is Control Flow?

Control flow determines the order in which code executes.

Without control flow:

System.out.println("Task 1");
System.out.println("Task 2");
System.out.println("Task 3");

The program will always do tasks in the same order.

Control flow allows:

• Decision making (if-else, switch)
• Repeating tasks (for, while, do-while)

1️⃣ if-else Statements

Used to execute code conditionally.

Syntax:

if(condition) {
    // code if condition is true
} else {
    // code if condition is false
}

Example:

int age = 18;

if(age >= 18) {
    System.out.println("You are an adult.");
} else {
    System.out.println("You are a minor.");
}

Output:

You are an adult.

else-if Ladder

When you have multiple conditions:

int marks = 75;

if(marks >= 90) {
    System.out.println("Grade A");
} else if(marks >= 75) {
    System.out.println("Grade B");
} else if(marks >= 50) {
    System.out.println("Grade C");
} else {
    System.out.println("Fail");
}

Output:

Grade B

2️⃣ switch Statement

Useful when multiple discrete values need checking.

Syntax:

switch(variable) {
    case value1:
        // code
        break;
    case value2:
        // code
        break;
    default:
        // code if no match
}

Example:

int day = 3;

switch(day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    case 3:
        System.out.println("Wednesday");
        break;
    default:
        System.out.println("Invalid day");
}

Output:

Wednesday

3️⃣ Loops in Java

Loops let you repeat code without writing it multiple times.

3.1 for Loop

for(int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}

Output:

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

3.2 while Loop

Executes while condition is true.

int i = 1;
while(i <= 5) {
    System.out.println("Count: " + i);
    i++;
}

3.3 do-while Loop

Executes at least once, then checks condition.

int i = 1;
do {
    System.out.println("Count: " + i);
    i++;
} while(i <= 5);

4️⃣ Break & Continue

• break → exits the loop immediately
• continue → skips current iteration and continues next

Example:

for(int i = 1; i <= 5; i++) {
    if(i == 3) continue; // skip 3
    System.out.println(i);
}

Output:

1
2
4
5

5️⃣ Combining Loops & Conditions

Practical example: Number guessing game

import java.util.Scanner;
import java.util.Random;

public class GuessNumber {
    public static void main(String[] args) {
        Random rand = new Random();
        int number = rand.nextInt(10) + 1; // 1-10
        Scanner sc = new Scanner(System.in);
        int guess;
        
        do {
            System.out.print("Guess a number (1-10): ");
            guess = sc.nextInt();
            
            if(guess < number) {
                System.out.println("Too low!");
            } else if(guess > number) {
                System.out.println("Too high!");
            } else {
                System.out.println("Correct! You win!");
            }
        } while(guess != number);
    }
}

Common Beginner Mistakes

• Forgetting {} for multiple statements in if/else
• Missing break in switch-case
• Infinite loops (forgetting increment/decrement)
• Using assignment = instead of comparison ==

Summary

In this article, you learned:

• if-else statements for decision making
• switch-case for multiple discrete values
• for, while, do-while loops for repeating tasks
• break & continue usage
• Combining loops and conditions for real-world logic

These control structures are the backbone of every Java program.

Next Article Preview 👀

Next week, we’ll explore:

• Arrays – store multiple values
• Strings – manipulate text
• StringBuilder vs StringBuffer

Get ready to organize and manipulate data like a pro!