While loop

The while loop repeats a block of code as long as the condition is true. The condition is checked before each iteration (pre‑test).

Syntax:

while (condition) {
    // loop body
}

Example:

int i = 0;
while (i < 5) {
    System.out.println(i);
    i++;
}

Infinite loop:

while (true) {
    // infinite loop, use break to exit
}

Reading input until sentinel:

Scanner scanner = new Scanner(System.in);
int sum = 0;
int input;
while ((input = scanner.nextInt()) != -1) {
    sum += input;
}
System.out.println("Sum: " + sum);

Important: Ensure the loop condition eventually becomes false to avoid infinite loops.