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.checks.coding;
  
  import com.puppycrawl.tools.checkstyle.StatelessCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  
  /**
   * <p>
   * Check that the {@code default} is after all the cases in a {@code switch} statement.
   * </p>
   * <p>
   * Rationale: Java allows {@code default} anywhere within the
   * {@code switch} statement. But it is more readable if it comes after the last {@code case}.
   * </p>
   * <ul>
   * <li>
   * Property {@code skipIfLastAndSharedWithCase} - Control whether to allow {@code default}
   * along with {@code case} if they are not last.
   * Type is {@code boolean}.
   * Default value is {@code false}.
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name=&quot;DefaultComesLast&quot;/&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * switch (i) {
   *   case 1:
   *     break;
   *   case 2:
   *     break;
   *   default: // OK
   *     break;
   * }
   *
   * switch (i) {
   *   case 1:
   *     break;
   *   case 2:
   *     break; // OK, no default
   * }
   *
   * switch (i) {
   *   case 1:
   *     break;
   *   default: // violation, 'default' before 'case'
   *     break;
   *   case 2:
   *     break;
   * }
   *
   * switch (i) {
   *   case 1:
   *   default: // violation, 'default' before 'case'
   *     break;
   *   case 2:
   *     break;
   * }
   * </pre>
   * <p>To configure the check to allow default label to be not last if it is shared with case:
   * </p>
   * <pre>
   * &lt;module name=&quot;DefaultComesLast&quot;&gt;
   *   &lt;property name=&quot;skipIfLastAndSharedWithCase&quot; value=&quot;true&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * switch (i) {
   *   case 1:
   *     break;
   *   case 2:
   *   default: // OK
   *     break;
   *   case 3:
   *     break;
   * }
   *
   * switch (i) {
   *   case 1:
   *     break;
   *   default: // violation
   *   case 2:
   *     break;
   * }
   *
   * // Switch rules are not subject to fall through, so this is still a violation:
   * switch (i) {
   *   case 1 -&gt; x = 9;
   *   default -&gt; x = 10; // violation
   *   case 2 -&gt; x = 32;
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code default.comes.last}
   * </li>
   * <li>
   * {@code default.comes.last.in.casegroup}
   * </li>
   * </ul>
   *
   * @since 3.4
   */
  @StatelessCheck
  public class DefaultComesLastCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "default.comes.last";
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE =
              "default.comes.last.in.casegroup";
  
      /** Control whether to allow {@code default} along with {@code case} if they are not last. */
      private boolean skipIfLastAndSharedWithCase;
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {
              TokenTypes.LITERAL_DEFAULT,
          };
      }
  
      /**
       * Setter to control whether to allow {@code default} along with
       * {@code case} if they are not last.
       *
       * @param newValue whether to ignore checking.
       */
      public void setSkipIfLastAndSharedWithCase(boolean newValue) {
          skipIfLastAndSharedWithCase = newValue;
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          final DetailAST defaultGroupAST = ast.getParent();
  
          // Switch rules are not subject to fall through.
          final boolean isSwitchRule = defaultGroupAST.getType() == TokenTypes.SWITCH_RULE;
  
          if (skipIfLastAndSharedWithCase && !isSwitchRule) {
              if (isNextSiblingOf(ast, TokenTypes.LITERAL_CASE)) {
                  log(ast, MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE);
              }
              else if (ast.getPreviousSibling() == null
                  && isNextSiblingOf(defaultGroupAST,
                                                     TokenTypes.CASE_GROUP)) {
                  log(ast, MSG_KEY);
              }
          }
          else if (isNextSiblingOf(defaultGroupAST,
                                              TokenTypes.CASE_GROUP)
                      || isNextSiblingOf(defaultGroupAST,
                                              TokenTypes.SWITCH_RULE)) {
              log(ast, MSG_KEY);
          }
      }
  
      /**
       * Return true only if passed tokenType in argument is found or returns false.
       *
       * @param ast root node.
       * @param tokenType tokentype to be processed.
       * @return true if desired token is found or else false.
       */
      private static boolean isNextSiblingOf(DetailAST ast, int tokenType) {
          return ast.getNextSibling() != null && ast.getNextSibling().getType() == tokenType;
      }
  
  }
  