irregularities with the setMaximumFractionDigits
===

In the code below, I am wondering why an exception will be thrown :

    [COde]

    import java.text.*;
     class NumFormat
        {
          public static void main(String[] args)throws Exception{
          String s = "123.456xyz";
          NumberFormat nf = NumberFormat.getInstance();
          System.out.println(nf.parse(s));
          nf.setMaximumFractionDigits(2);
         System.out.println(nf.format(s));
        }
     }
    [/Code]