A DESCRIPTION OF THE PROBLEM :
There are missing @return tags for almost all showInputDialog method() and some methods doesn't contain throws HeadlessException declaration for examle method showInputDialog(Object message, Object initialSelectionValue).

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
It should be same as for showInputDialog(Component parentComponent,
        Object message, String title, int messageType, Icon icon,
        Object[] selectionValues, Object initialSelectionValue)
        throws HeadlessException method
ACTUAL -
    /**
     * Shows a question-message dialog requesting input from the user, with
     * the input value initialized to <code>initialSelectionValue</code>. The
     * dialog uses the default frame, which usually means it is centered on
     * the screen.
     *
     * @param message the <code>Object</code> to display
     * @param initialSelectionValue the value used to initialize the input
     * field
     * @since 1.4
     */

Missing @return and @exception tags

URL OF FAULTY DOCUMENTATION :
http://java.sun.com/javase/6/docs/api/