import java.util.Arrays;

public class Demo2
{

    public static void main(String[] args)
    {
	Double[] a = new Double[3];

	a[0] = 3.0;
	a[1] = 2.0;
	a[2] = 1.0;

	System.out.println( Arrays.toString(a) );

	exch(a, 0, 2);		// Cannot apply to Double...

	System.out.println( Arrays.toString(a) );
    }

    private static void exch( Integer[] a, int i, int j )
    {
        Integer help;

        help = a[i];
        a[i] = a[j];
        a[j] = help;
    }
}