java loops

import java.util.Scanner;
public class p2
{
    public static void main(String args[])
    {
        Scanner s1=new Scanner(System.in);
        int a,b,ans;
        System.out.println("Enter the first Value: ");
        a=s1.nextInt();
        System.out.println(" FOR LOOP EXAMPLE");
        for(b=1;b<=10;b++)
        {
            ans=b*a;
            System.out.println(a+" X "+b+" = "+ans);
        }
        System.out.println(" While LOOP EXAMPLE");
        while(b!=21)
        {
            ans=b*a;
            System.out.println(a+" X "+b+" = "+ans);
            b+=1;
        }
        System.out.println("DO While LOOP EXAMPLE");
        do
        {
                ans=b*a;
            System.out.println(a+" X "+b+" = "+ans);
            b+=1;
        }while(b<=30);
    }
}