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.naming;
  
  import java.util.regex.Pattern;
  
  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;
  import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
  
  /**
   * Abstract class for checking that names conform to a specified format.
   *
   */
  @StatelessCheck
  public abstract class AbstractNameCheck
      extends AbstractCheck {
  
      /**
       * Message key for invalid pattern violation.
       */
      public static final String MSG_INVALID_PATTERN = "name.invalidPattern";
  
      /** The regexp to match against. */
      private Pattern format;
  
      /**
       * Creates a new {@code AbstractNameCheck} instance.
       *
       * @param format format to check with
       */
      protected AbstractNameCheck(String format) {
          this.format = CommonUtil.createPattern(format);
      }
  
      /**
       * Decides whether the name of an AST should be checked against
       * the format regexp.
       *
       * @param ast the AST to check.
       * @return true if the IDENT subnode of ast should be checked against
       *     the format regexp.
       */
      protected abstract boolean mustCheckName(DetailAST ast);
  
      /**
       * Set the format for the specified regular expression.
       *
       * @param pattern the new pattern
       */
      public final void setFormat(Pattern pattern) {
          format = pattern;
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          if (mustCheckName(ast)) {
              final DetailAST nameAST = ast.findFirstToken(TokenTypes.IDENT);
              if (!format.matcher(nameAST.getText()).find()) {
                  log(nameAST,
                      MSG_INVALID_PATTERN,
                      nameAST.getText(),
                      format.pattern());
              }
          }
      }
  
  }
  