code: public void write(String str, int off, int len)  {
      	char[] chars = new char[len];
      	str.getChars(off, off+len, chars, 0);
      	buf.append(chars);
      }
docs: Write a portion of a string.
  
  @param  str  String to be written
  @param  off  Offset from which to start writing characters
  @param  len  Number of characters to write