Abrir um novo JFrame

public class Tela extends JFrame implements ActionListener {
	
	private static final long serialVersionUID = 1L;

	private final JButton bt = new JButton("Nova Tela");
	
	public Tela(){

		setTitle( "Tela 1" );
		setVisible( true );
		setSize( 500, 400 );
		setLocation( 200, 100 );
	
		
		add(bt);
		bt.setBounds( 10, 10, 100, 20 );
		setLayout( null );
		bt.addActionListener( this );
	}
	public void actionPerformed( ActionEvent e ) {
		
		Tela2 tl = new Tela2();
		
		if(e.getSource() == bt ){
			
			add(tl);
		}
	}
	public static void main(String[] args ){
		new Tela();
	}
}

public class Tela2  extends JInternalFrame{

	public Tela2(){
		
		super( "Tela2", true, true, true, true );
		setVisible( true );
		setSize( 200, 200 );
		setLocation( 100, 100 );
	}
}