public void write(String str, int off, int len)  {
    	char[] chars = new char[len];
    	str.getChars(off, off+len, chars, 0);
    	buf.append(chars);
    }
public void write ( String str , int off , int len ) { char [ ] chars = new char [ len ] ; str . getChars ( off , off + len , chars , 0 ) ; buf . append ( chars ) ; }
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