Question

I am asked to print multiples of 2 only with a never ending loop.

Attempt:

import java.util.Scanner;

public class Infiniteloop {

    public static void main (String [] args) 
    {
        Scanner input=new Scanner (System.in);
        int number,x;
        System.out.print("Enter a number");

        number=input.nextInt();
        if(number%2==0)
        {
            while(number>=0)
            {
                x= (++number);
                System.out.println(x);
            }
        }
    }
}

I can only use while-loop. So I tried to set the remainder of 2 equal to zero. I tried using the counter but it doesnt increment it. Keeps printing out zeros. I need some help. Thanks.

Answer 1

Supposing that you want to prompt the user for a start number and then print all the following even numbers:

number = input.nextInt(); //read the input
number += number % 2; //if input is odd, add 1
while (true)
{
   System.out.println (number);
   number += 2;
}

Supposing you want to check for even numbers:

while (true)
{
  number = input.nextInt();
  if (number % 2 == 0) System.out.println (number);
}

Or if you don’t care about empty lines:

while (true) System.out.println (input.nextInt () % 2 == 0 ? "even" : "");

EDIT: Same thing for powers of two:

public static void main (String [] args)
{
    Scanner input = new Scanner (System.in);
    int number;
    while (true)
    {
        System.out.print ("Enter a number");
        number = input.nextInt ();
        while ( (number & 1) == 0) number >>= 1;
        if (number == 1) System.out.println ("Perfect divisor.");
    }