// Find all perfect numbers less than 
// or equal to then entered upper bound.

import javax.swing.JOptionPane;
    
public class Perfect
{
    public static void main(String[] args)
    {
        int upperBound, n, factor, sum;

        upperBound = Integer.parseInt(JOptionPane.showInputDialog(
                "Enter upper bound for perfect number search"));
    
        for(n = 2; n <= upperBound; n++)
        {
            sum = 0;
            for(factor = 1; factor <= n / 2; factor++)
                if (n % factor == 0)
                    sum += factor;

            if (n == sum)
                System.out.println(n);
        }
    }
}

// Prompt of input dialog:
Upper bound for perfect number search:

// Sample input to input dialog:
10000

// Output in Terminal Window:
6
28
496
8128