hiding title bar of JInternalFrame? -java

I found some code online, I edited it a bit. I want to hide title bar of a JInternalFrame.

  JInternalFrame frame = new JInternalFrame();
  // Get the title bar and set it to null
  setRootPaneCheckingEnabled(false);
  javax.swing.plaf.InternalFrameUI ifu= frame.getUI();
  ((javax.swing.plaf.basic.BasicInternalFrameUI)ifu).setNorthPane(null);      

  frame.setLocation(i*50+10, i*50+10);
  frame.setSize(200, 150);
  //frame.setBackground(Color.white);      

  frame.setVisible(true);
  desktop.add(frame);

The problem is that the title bar isn't being hidden for some reason. Thanks.