Loops can execute a block of code as long as a specified condition is reached.

Loops are handy because they save time, reduce errors, and they make code more readable.
The while loop loops through a block of code as long as a specified condition is true:

public static int no = 10;
    public static int num = 3;
    public static int No = 15;
    public static int a = 22;

    public static void main(String[] args) {
        // ******************10 8 6 4 2******************
        while (no >= 1) {
            System.out.print(no + " ");
            no = no - 2;
        }
        // ******************3 6 9 12 15******************
        System.out.println();

        while (num <= 15) {
            System.out.print(num + " ");
            num = num + 3;
        }
        System.out.println();
        // ******************15 12 9 6 3******************
        while (No >= 3) {
            System.out.print(No + " ");
            No = No - 3;
        }

    }