code: public void setValueSelected(T value, boolean selected) {
          int idx = getIndex(value);
          if (idx >= 0) {
              setItemSelectedInternal(idx, selected);
          }
      }
docs: Sets whether an individual list value is selected.
  
  @param value    the value of the item to be selected or unselected
  @param selected <code>true</code> to select the item