Control Flow: Conditionals & Loops

Duration: 7.0 min

Control Flow: Conditionals & Loops

Control flow determines the order in which statements execute. Java provides if/else for conditionals and for/while loops for repetition. Mastering control flow is essential for writing programs that respond to different conditions and process data efficiently. Understanding how to structure your code with proper control flow makes it more readable and maintainable.

public class IfElse {
    public static void main(String[] args) {
        int age = 20;
        if (age >= 18) System.out.println("Adult");
        else System.out.println("Minor");
    }
}

Adult

public class IfElseIf {
    public static void main(String[] args) {
        int score = 75;
        if (score >= 90) System.out.println("A");
        else if (score >= 80) System.out.println("B");
        else if (score >= 70) System.out.println("C");
        else System.out.println("F");
    }
}

C

public class Switch {
    public static void main(String[] args) {
        int day = 3;
        switch (day) {
            case 1: System.out.println("Mon"); break;
            case 2: System.out.println("Tue"); break;
            case 3: System.out.println("Wed"); break;
            default: System.out.println("Other");
        }
    }
}

Wed

public class ForLoop {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) System.out.println(i);
    }
}

1
2
3
4
5

public class WhileLoop {
    public static void main(String[] args) {
        int i = 1;
        while (i <= 3) {
            System.out.println(i);
            i++;
        }
    }
}

1
2
3

public class DoWhile {
    public static void main(String[] args) {
        int i = 1;
        do {
            System.out.println(i);
            i++;
        } while (i <= 3);
    }
}

1
2
3

public class BreakContinue {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            if (i == 3) continue;
            if (i == 5) break;
            System.out.println(i);
        }
    }
}

1
2
4

public class NestedLoop {
    public static void main(String[] args) {
        for (int i = 1; i <= 2; i++)
            for (int j = 1; j <= 2; j++)
                System.out.println("i=" + i + ", j=" + j);
    }
}

i=1, j=1
i=1, j=2
i=2, j=1
i=2, j=2

public class Ternary {
    public static void main(String[] args) {
        int age = 20;
        String status = (age >= 18) ? "Adult" : "Minor";
        System.out.println(status);
    }
}

Adult

public class EnhancedFor {
    public static void main(String[] args) {
        int[] nums = {1, 2, 3, 4, 5};
        for (int num : nums) System.out.println(num);
    }
}

1
2
3
4
5

public class LoopLabels {
    public static void main(String[] args) {
        outer: for (int i = 1; i <= 3; i++) {
            for (int j = 1; j <= 3; j++) {
                if (i == 2 && j == 2) break outer;
                System.out.println("i=" + i + ", j=" + j);
            }
        }
    }
}

i=1, j=1
i=1, j=2
i=1, j=3
i=2, j=1

💡 Tip: Best Practice: Use break in switch statements to prevent fall-through to the next case.

💡 Tip: Common Mistake: Infinite loops occur when the loop condition never becomes false. Always ensure your loop has a proper exit condition.

Learn more: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/if.html