Jcombobox

private void jCBoxtipodeContActionPerformed(java.awt.event.ActionEvent evt) {                                                  
       if(jCBoxtipodeCont.getSelectedItem().equals("E-mail")){  
           new Email().setVisible(true);

// FramePrincipal
public class FramePrincipal extends JFrame {

	private JPanel contentPane;
	private JComboBox meuCombo;

	
	/**
	 * Create the frame.
	 */
	public FramePrincipal() {
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setLocationRelativeTo(null);
		setBounds(100, 100, 450, 300);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		setContentPane(contentPane);
		contentPane.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
		
		JLabel lblEscolhaOFrame = new JLabel("Escolha o frame pra exibir");
		contentPane.add(lblEscolhaOFrame);
		
		meuCombo = new JComboBox();
		meuCombo.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(meuCombo.getSelectedItem().toString().equals("Frame2")){
					new Frame2().setVisible(true);
				}else if(meuCombo.getSelectedItem().toString().equals("Frame3")){
					new Frame3().setVisible(true);
				}
			}
		});
		meuCombo.setModel(new DefaultComboBoxModel(new String[] {"Frame2", "Frame3"}));
		contentPane.add(meuCombo);
	}

}


// Frame2 q sera escolhido no JComboBox do FramePrincipal
public class Frame2 extends JDialog {

	private final JPanel contentPanel = new JPanel();

	
	/**
	 * Create the dialog.
	 */
	public Frame2() {
		setBounds(100, 100, 450, 300);
		getContentPane().setLayout(new BorderLayout());
		contentPanel.setLayout(new FlowLayout());
		contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
		getContentPane().add(contentPanel, BorderLayout.CENTER);
		{
			JLabel lblFrame = new JLabel("Frame2");
			contentPanel.add(lblFrame);
		}
		{
			JPanel buttonPane = new JPanel();
			buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
			getContentPane().add(buttonPane, BorderLayout.SOUTH);
			{
				JButton okButton = new JButton("OK");
				okButton.setActionCommand("OK");
				buttonPane.add(okButton);
				getRootPane().setDefaultButton(okButton);
			}
			{
				JButton cancelButton = new JButton("Cancel");
				cancelButton.setActionCommand("Cancel");
				buttonPane.add(cancelButton);
			}
		}
	}
}


// Frame3 q sera escolhido no JComboBox do FramePrincipal
public class Frame3 extends JDialog {

	private final JPanel contentPanel = new JPanel();
	

	/**
	 * Create the dialog.
	 */
	public Frame3() {
		setBounds(100, 100, 450, 300);
		getContentPane().setLayout(new BorderLayout());
		contentPanel.setLayout(new FlowLayout());
		contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
		getContentPane().add(contentPanel, BorderLayout.CENTER);
		{
			JLabel lblFrame = new JLabel("Frame3");
			contentPanel.add(lblFrame);
		}
		{
			JPanel buttonPane = new JPanel();
			buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
			getContentPane().add(buttonPane, BorderLayout.SOUTH);
			{
				JButton okButton = new JButton("OK");
				okButton.setActionCommand("OK");
				buttonPane.add(okButton);
				getRootPane().setDefaultButton(okButton);
			}
			{
				JButton cancelButton = new JButton("Cancel");
				cancelButton.setActionCommand("Cancel");
				buttonPane.add(cancelButton);
			}
		}
	}
}


// classe Main = main
public class Main {
		/**
		 * Launch the application.
		 */
		public static void main(String[] args) {
			EventQueue.invokeLater(new Runnable() {
				public void run() {
					try {
						FramePrincipal frame = new FramePrincipal();
						frame.setVisible(true);
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			});
		}
		
}