Use getMaximumFractionDigits(), setMaximumFractionDigits(), parse(), and setParseIntegerOnly(): : Formatter « Utility Classes « SCJP

1. SCJP
2. Utility Classes
3. Formatter

import java.text.NumberFormat;
import java.text.ParseException;

public class MainClass {
  public static void main(String[] argv) {
    float f1 = 123.45678f;
    NumberFormat nf = NumberFormat.getInstance();
    System.out.print(nf.getMaximumFractionDigits() + " ");
    System.out.print(nf.format(f1) + "  ");

    nf.setMaximumFractionDigits(5);
    System.out.println(nf.format(f1) + "  ");

    try {
      System.out.println(nf.parse("1234.567"));
      nf.setParseIntegerOnly(true);
      System.out.println(nf.parse("1234.567"));
    } catch (ParseException pe) {
      System.out.println("parse exc");
    }

  }
}

3 123.457  123.45678  
1234.567
1234