if (name == null) return;  if (parent.getLayout() != this) throw new IllegalArgumentException("parent's layout is not this CardLayout");
  public void show (Container parent, String name)  {    Object target = tab.get (name);    if (target != null)      {	int num = parent.ncomponents;	// This is more efficient than calling getComponents().	Component[] comps = parent.component;	for (int i = 0; i < num; ++i)	  {	    if (comps[i].isVisible())	      {		if (target == comps[i])		  return;		comps[i].setVisible (false);	      }	  }	((Component) target).setVisible (true);      }  }