private void scrollBy(final int increment){
  index+=increment;
  if (index < 0) {
    index=0;
  }
  if (index >= items.size()) {
    index=items.size() - 1;
  }
  redraw();
}

private void scrollBy ( final int increment ) { index += increment ; if ( index < 0 ) { index = 0 ; } if ( index >= items . size ( ) ) { index = items . size ( ) - 1 ; } redraw ( ) ; }
scroll the selected item
