Lesson 12: Iteration: for, while, and do-while Loops

Loops allow you to repeatedly execute a block of code until a certain condition is met.

1. The for Loop

Ideal when you know exactly how many times you need to iterate (e.g., looping through an array).

Structure: for (initialization; condition; update) { ... }

java // Print numbers from 1 to 5 for (int i = 1; i <= 5; i++) { System.out.println("Count: " + i); }

Enhanced for Loop (For-Each)

Used for iterating over arrays or collections easily, without needing an index.

java String[] fruits = {"Apple", "Banana", "Cherry"};

for (String fruit : fruits) { System.out.println(fruit); }

2. The while Loop

Executes a block of code as long as the specified condition is true. Ideal when the number of iterations is unknown beforehand.

java int counter = 0; while (counter < 3) { System.out.println("Running..."); counter++; } // Important: Ensure the condition eventually becomes false to avoid an infinite loop.

3. The do-while Loop

Similar to while, but guarantees that the loop body executes at least once, because the condition is checked at the end.

java int input = 0; do { System.out.println("Please enter a number greater than 10:"); // Assume we read input here (e.g., using Scanner) // For demonstration, we'll set it to 15 after the first run if (input == 0) input = 15; } while (input < 10);

System.out.println("Input accepted.");

4. Control Flow inside Loops (break and continue)

• break: Immediately terminates the innermost loop or switch structure.
• continue: Skips the rest of the current iteration and jumps to the next iteration.