The ability manipulate the Quit button and process Quit events

public class InstallerFrame  {

     public Navigator getNavigator() { ... }

}

public interface Navigator
{

    /**
     * Returns the button to navigate to the next panel.
     *
     * @return the 'next' button
     */
    JButton getNext();

    /**
     * Registers a listener that may veto navigation to the next panel.
     *
     * @param listener the listener. May be <tt>null</tt>
     */
    void setNextListener(VetoableEventListener listener);

    /**
     * Returns the button to navigate to the previous panel.
     *
     * @return the 'previous' button
     */
    JButton getPrevious();

    /**
     * Registers a listener that may veto navigation to the previous panel.
     *
     * @param listener the listener. May be <tt>null</tt>
     */
    void setPreviousListener(VetoableEventListener listener);

    /**
     * Returns the button to quit installation.
     *
     * @return the 'quit' button
     */
    JButton getQuit();

    /**
     * Registers a listener that may veto quitting installation.
     *
     * @param listener the listener. May be <tt>null</tt>
     */
    void setQuitListener(VetoableEventListener listener);

    /**
     * Navigates to the next panel.
     *
     * @return <tt>true</tt> if the next panel was displayed, or <tt>false</tt> if the last panel is displayed or
     *         navigation is vetoed
     */
    boolean next();

    /**
     * Navigates to the previous panel.
     *
     * @return <tt>true</tt> if the previous panel was displayed, or <tt>false</tt> if the first panel is displayed or
     *         navigation is vetoed
     */
    boolean previous();

    /**
     * Quits installation.
     *
     * @return <tt>true</tt> if installation was quit, or <tt>false</tt> if quit failed was vetoed
     */
    boolean quit();

}

public interface VetoableEventListener extends EventListener
{

    /**
     * Invoked to determine if an event should be vetoed.
     *
     * @param source the source that triggered the event
     * @return <tt>true</tt> if the event should be vetoed, or <tt>false</tt> if it should proceed
     */
    boolean veto(Object source);
}

navigator.getQuit().setEnabled(false);
navigator.getQuit().setVisible(false);