Count Number Of Digits After Decimal Point?

Given a Numbers instance, whose fields are arrays of all the built-in Java numeric types (int, long, float, double, big-decimal, etc), write a method to sort all the numbers into a master list, and then print out the numbers where the number of digits past the decimal point is equal to the index of the number in the master list.

Is there a function in Java that will give me just the numbers after the decimal? I tried Decimalformat but couldn't get it to work. Here is what I have so far; however, I think I might be on the wrong track.

public class Numbers
{
public static void main(String[] args) {
Byte bNum = new Byte((byte) -50);
Integer iNum = new Integer(168);
Long lNum = new Long(100000L);
Short sNum = new Short((short) 10000);
Float fNum = new Float(12.19f);
Double dNum = new Double(23.123);
BigDecimal bd = new BigDecimal("3.14159265358979323846");

[code]....