Calling Restart workbench code only once

I created a preference page with multiple fields. On preference store I added propertychangelistener when contains code to restart application.

getPreferenceStore().addPropertyChangeListener(new IPropertyChangeListener() {

      @Override
      public void propertyChange(PropertyChangeEvent event) {
        if(MessageDialog.openConfirm(shell,"Restart Required", "Restart now?"))
          PlatformUI.getWorkbench().restart();
      }
    });

Problem is when I change multiple entries in preference page this restart code will be called that many times. What condition should I put so that even after changing multiple entries this restart will be called once only.

Just set a flag in the property change listener and do the restart prompt in the performOk method of the page.

// Field in the page:
boolean restartRequired = false;


getPreferenceStore().addPropertyChangeListener(new IPropertyChangeListener() {

  @Override
  public void propertyChange(PropertyChangeEvent event) {
    restartRequired = true;
  }
});


@Override
public boolean performOk()
{ 
  if (restartRequired) {
    ... prompt / restart
  }
  return super.performOk();
}