Java for Beginners – Control Flow in Java Decisions & Loops

 

1. What is Control Flow?

Control flow decides which part of your code runs and how many times it runs.
It’s like giving your program the ability to make choices and repeat tasks.

There are two main types:

1. Decision-making statements (if-else, switch)

2. Looping statements (for, while, do-while)

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2. Decision-Making Statements

A) if Statement

Runs code only if the condition is true.

int age = 20;
if (age >= 18) {
    System.out.println("You are an adult.");
}

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B) if-else Statement

Chooses between two options.

if (age >= 18) {
    System.out.println("Adult");
} else {
    System.out.println("Minor");
}

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C) if-else-if Ladder

Chooses between multiple options.

int marks = 85;
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");
}

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D) switch Statement

Better for checking multiple exact matches.

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");
}

Note: Always use break to stop the switch from running other cases.

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3. Looping Statements

A) for Loop – Runs a fixed number of times.

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

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B) while Loop – Runs while the condition is true.

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

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C) do-while Loop – Runs at least once, then checks the condition.

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

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4. Jump Statements

A) break – Exits a loop early.

for (int i = 1; i <= 10; i++) {
    if (i == 5) {
        break; // stop when i is 5
    }
    System.out.println(i);
}

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B) continue – Skips the current loop iteration.

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

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5. Nested Loops

A loop inside another loop.
Example: Multiplication table.

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
        System.out.print(i * j + " ");
    }
    System.out.println();
}

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6. Mini Practice Exercises

Task 1: Write a program that checks if a number is even or odd.
Task 2: Print a multiplication table for numbers 1 to 10.
Task 3: Create a menu-driven program using switch where a user chooses a shape and the program calculates its area.

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7. What’s Next?

In Blog 4, we’ll dive into:

• Functions (methods) in Java

• Method parameters & return values

• Method overloading

• Basics of Object-Oriented Programming (Classes & Objects)

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💡 Tip: Play with loops to create patterns (like triangles, squares) — it’s a fun way to master control flow.