code: public synchronized CheckBoxList<V> setChecked(V object, boolean checked) {
          int index = indexOf(object);
          if(index != -1) {
              setChecked(index, checked);
          }
          return self();
      }
docs: Programmatically sets the checked state of an item in the list box
  @param object Object to set the checked state of
  @param checked If {@code true}, then the item is set to checked, otherwise not
  @return Itself