if (previous != null)
  public void focusPreviousComponent (Component comp)  {    Component focusComp = (comp == null) ? getGlobalFocusOwner () : comp;    Container focusCycleRoot = focusComp.getFocusCycleRootAncestor ();    FocusTraversalPolicy policy = focusCycleRoot.getFocusTraversalPolicy ();    Component previous = policy.getComponentBefore (focusCycleRoot, focusComp);    previous.requestFocusInWindow ();  }