Loops & Control Flow

☕ Java Lesson 6 Beginner

Loops repeat code blocks as long as a condition remains true. Java features three primary loop constructs: for, while, and do-while.

1 Loop Structures: while, do-while, and for

Different loop configurations suit different tasks:

while: Evaluates its condition before checking the block. May execute 0 times.
do-while: Executes the block first, then evaluates the condition. Guaranteed to run at least once!
for: Best when the iteration count is known beforehand. Declares initializer, condition, and step increment in one line.

2 Iteration Tracing & Loop Control (Break / Continue)

Loop execution can be dynamically controlled:

break: Terminates the loop structure immediately.
continue: Skips the remaining statement blocks in the current iteration and jumps to the next condition evaluation.

Java — Loops and Flow Control ▶ Run Code

public class Main {
    public static void main(String[] args) {
        // Standard For Loop
        System.out.print("For iteration: ");
        for (int i = 1; i <= 5; i++) {
            System.out.print(i + " ");
        }
        System.out.println();

        // While Loop with loop control
        System.out.print("While iteration (skipping 3, breaking at 6): ");
        int count = 1;
        while (count <= 10) {
            if (count == 3) {
                count++;
                continue; // Skip printing 3
            }
            if (count == 6) {
                break; // Exit loop completely
            }
            System.out.print(count + " ");
            count++;
        }
        System.out.println();

        // Do-While loop execution guarantee
        int val = 100;
        do {
            System.out.println("Do-while block runs even though condition is false!");
        } while (val < 10);
    }
}

3 Code Challenge

Challenge: Write a program that uses a loop to compute the sum of all odd numbers between 1 and 20. Print the final computed sum. Extend it by adding a check inside the loop to skip the number 9 completely using the `continue` keyword.