code: private void cancelButtonActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_cancelButtonActionPerformed
          feedback = UserFeedback.Cancel;
          synchronized (WAITER_LOCK) {
              okButton.setEnabled(false);
              cancelButton.setEnabled(false);
              WAITER_LOCK.notifyAll();
          }
      }
docs: GEN-LAST:event_okButtonActionPerformed