public class Main
{
    public static void main( String[] args )
    {
        // test the formula a bit
        double d1 = distance(-2,1 , 1,5);
        System.out.println(" (-2,1) to (1,5) => " + d1 );

        double d2 = distance(-2,-3 , -4,4);
        System.out.println(" (-2,-3) to (-4,4) => " + d2 );

        System.out.println(" (2,-3) to (-1,-2) => " + distance(2,-3,-1,-2) );

        System.out.println(" (4,5) to (4,5) => " + distance(4,5,4,5) );
    }

    public static double distance( int x1, int y1, int x2, int y2 )
    {
        double d = Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
        return d;
    }
}