JOptionPane YES NO OPTION

You should actually take the result from the option pane:

dialogButton = JOptionPane.showConfirmDialog (null, "Are you sure?","WARNING", dialogButton);

Otherwise, it remains set to JOptionPane.YES_NO_OPTION.

Cleaner would be:

if (JOptionPane.showConfirmDialog(null, "Are you sure?", "WARNING",
        JOptionPane.YES_NO_OPTION) == JOptionPane.YES_OPTION) {
    // yes option
} else {
    // no option
}

Although, I’m not sure what this line is expected to do in the posted code: remove(dialogButton);.

For more details and examples check out How to Make Dialogs tutorial.