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;
  
  import java.io.Serializable;
  
  /**
   * Thread mode settings for the checkstyle modules.
   *
   * @noinspection SerializableHasSerializationMethods
   * @noinspectionreason SerializableHasSerializationMethods - we only need serialVersionUID
   *      to differentiate between threads
   */
  public class ThreadModeSettings implements Serializable {
  
      /** A checker module name. */
      public static final String CHECKER_MODULE_NAME = Checker.class.getSimpleName();
  
      /** A multi thread checker module name. */
      public static final String MULTI_THREAD_CHECKER_MODULE_NAME =
              Checker.class.getSimpleName();
  
      /** A three walker module name. */
      public static final String TREE_WALKER_MODULE_NAME = TreeWalker.class.getSimpleName();
  
      /** A multi thread three walker module name. */
      public static final String MULTI_THREAD_TREE_WALKER_MODULE_NAME =
              TreeWalker.class.getSimpleName();
  
      /** A single thread mode settings instance. */
      public static final ThreadModeSettings SINGLE_THREAD_MODE_INSTANCE =
              new ThreadModeSettings(1, 1);
  
      /** A unique serial version identifier. */
      private static final long serialVersionUID = 1L;
  
      /** The checker threads number. */
      private final int checkerThreadsNumber;
      /** The tree walker threads number. */
      private final int treeWalkerThreadsNumber;
  
      /**
       * Initializes the thread mode configuration.
       *
       * @param checkerThreadsNumber the Checker threads number
       * @param treeWalkerThreadsNumber the TreeWalker threads number
       */
      public ThreadModeSettings(int checkerThreadsNumber, int treeWalkerThreadsNumber) {
          this.checkerThreadsNumber = checkerThreadsNumber;
          this.treeWalkerThreadsNumber = treeWalkerThreadsNumber;
      }
  
      /**
       * Gets the number of threads for the Checker module.
       *
       * @return the number of threads for the Checker module.
       */
      public int getCheckerThreadsNumber() {
          return checkerThreadsNumber;
      }
  
      /**
       * Gets the number of threads for the TreeWalker module.
       *
       * @return the number of threads for the TreeWalker module.
       */
      public int getTreeWalkerThreadsNumber() {
          return treeWalkerThreadsNumber;
      }
  
      /**
       * Resolves the module name according to the thread settings.
       *
       * @param name The original module name.
       * @return resolved module name.
       * @throws IllegalArgumentException when name is Checker or TreeWalker
       */
      public final String resolveName(String name) {
          if (checkerThreadsNumber > 1) {
              if (CHECKER_MODULE_NAME.equals(name)) {
                  throw new IllegalArgumentException(
                          "Multi thread mode for Checker module is not implemented");
              }
              if (TREE_WALKER_MODULE_NAME.equals(name)) {
                  throw new IllegalArgumentException(
                          "Multi thread mode for TreeWalker module is not implemented");
              }
          }
  
          return name;
      }
  
  }
  