code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.gui;
  
  import java.util.EventObject;
  
  import javax.swing.CellEditor;
  import javax.swing.event.CellEditorListener;
  import javax.swing.event.ChangeEvent;
  import javax.swing.event.EventListenerList;
  
  /**
   * A base class for CellEditors, providing default implementations for all
   * methods in the CellEditor interface and support for managing a series
   * of listeners.
   * <a href=
   * "https://docs.oracle.com/cd/E48246_01/apirefs.1111/e13403/oracle/ide/controls/TreeTableModel.html">
   * Original&nbsp;Source&nbsp;Location</a>
   *
   */
  public class BaseCellEditor implements CellEditor {
  
      /**
       * A list of event listeners for the cell editor.
       */
      private final EventListenerList listenerList = new EventListenerList();
  
      @Override
      public Object getCellEditorValue() {
          return null;
      }
  
      @Override
      public boolean isCellEditable(EventObject event) {
          return true;
      }
  
      @Override
      public boolean shouldSelectCell(EventObject anEvent) {
          return false;
      }
  
      @Override
      public boolean stopCellEditing() {
          return true;
      }
  
      @Override
      public void cancelCellEditing() {
          // No code, tree is read-only
      }
  
      @Override
      public void addCellEditorListener(CellEditorListener listener) {
          listenerList.add(CellEditorListener.class, listener);
      }
  
      @Override
      public void removeCellEditorListener(CellEditorListener listener) {
          listenerList.remove(CellEditorListener.class, listener);
      }
  
      /**
       * Notifies all listeners that have registered interest in
       * 'editing stopped' event.
       *
       * @see EventListenerList
       */
      protected void fireEditingStopped() {
          // Guaranteed to return a non-null array
          final Object[] listeners = listenerList.getListenerList();
          // Process the listeners last to first, notifying
          // those that are interested in this event
          for (int i = listeners.length - 2; i >= 0; i -= 2) {
              if (listeners[i] == CellEditorListener.class) {
                  ((CellEditorListener) listeners[i + 1]).editingStopped(new ChangeEvent(this));
              }
          }
      }
  
      /**
       * Notifies all listeners that have registered interest in
       * 'editing canceled' event.
       *
       * @see EventListenerList
       */
      protected void fireEditingCanceled() {
          // Guaranteed to return a non-null array
          final Object[] listeners = listenerList.getListenerList();
          // Process the listeners last to first, notifying
          // those that are interested in this event
          for (int i = listeners.length - 2; i >= 0; i -= 2) {
              if (listeners[i] == CellEditorListener.class) {
                  ((CellEditorListener) listeners[i + 1]).editingCanceled(new ChangeEvent(this));
              }
          }
      }
  
  }
  