Introduction to the while Loop

Loops help you repeat actions in your Java programs without writing the same code multiple times. The while loop is a fundamental tool for this purpose. It keeps running a block of code as long as a specific condition remains true. This allows you to process data, check user input, or perform calculations until a certain requirement is met.

Here is the basic idea of a while loop in pseudocode:

while (condition is true){
    // run this block of code
}

You use a while loop when you do not always know beforehand how many times you need to repeat an action. The loop checks the condition before every repetition, so as soon as the condition becomes false, the loop stops running.

You will learn how to write and control while loops, and see how they are used in real Java programs.

Imagine you want to calculate the sum of numbers from 1 to 5. Instead of adding each number manually, you can use a while loop to do it automatically.

Step-by-step breakdown of a while loop

1. Initialization: Set up the variable that will be used in the loop condition;
2. Loop Condition: The while loop checks a condition before each iteration; if the condition is true, the loop body runs;
3. Loop Body: Code inside the loop executes each time the condition is true;
4. Iteration: Update the loop variable inside the body to eventually make the condition false and end the loop.

Example

int count = 1; // Step 1: Initialization
while (count <= 5) { // Step 2: Condition checked before each loop
    System.out.println("Count is: " + count); // Step 3: Loop body runs
    count++; // Step 4: Iteration (update variable)
}

• The loop starts with count set to 1;
• Each time, the condition count <= 5 is checked;
• If true, the loop prints the current value and increases count by 1;
• When count becomes 6, the condition is false and the loop stops.