Component contentPane = frame.getContentPane(); if (contentPane != null && contentPane.getBackground() instanceof UIResource) { contentPane.setBackground(null); }
  protected void installDefaults()    {      internalFrameLayout = createLayoutManager();      frame.setLayout(internalFrameLayout);      LookAndFeel.installBorder(frame, "InternalFrame.border");      frame.setFrameIcon(UIManager.getIcon("InternalFrame.icon"));  }