Format file length in string in Java

//from ww w  .j  a v  a  2s . c o m
public class Main {
  public static void main(String[] argv){
    System.out.println(format(123123123L));
  }
  public static final String format(long l) {

    String s = String.valueOf(l);
    int digits = 0;
    while (s.length() > 3) {
      s = s.substring(0, s.length() - 3);
      digits++;
    }
    StringBuffer buffer = new StringBuffer();
    buffer.append(s);
    if ((s.length() == 1) && (String.valueOf(l).length() >= 3)) {
      buffer.append(".");
      buffer.append(String.valueOf(l).substring(1, 3));
    } else if ((s.length() == 2) && (String.valueOf(l).length() >= 3)) {
      buffer.append(".");
      buffer.append(String.valueOf(l).substring(2, 3));
    }
    if (digits == 0) {
      buffer.append(" B");
    } else if (digits == 1) {
      buffer.append(" KB");
    } else if (digits == 2) {
      buffer.append(" MB");
    } else if (digits == 3) {
      buffer.append(" GB");
    } else if (digits == 4) {
      buffer.append(" TB");
    }
    return buffer.toString();

  }

}