docs: public IStringBuffer append( char[] chars, int start, int length )
      {
          if ( chars == null )
              throw new NullPointerException();
          if ( start < 0 )
              throw new IndexOutOfBoundsException();
          if ( length <= 0 )
              throw new IndexOutOfBoundsException();
          if ( start + length > chars.length ) 
              throw new IndexOutOfBoundsException();
          
          //check the necessary to resize the buffer.
          if ( count + length > buff.length ) {
              resizeTo( (count + length) * 2 + 1 );
          }
          
          for ( int j = 0; j < length; j++ ) {
              buff[count++] = chars[start+j];
          }
          
          return this;
      }