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;
  
  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.utils.CommonUtil;
  
  /**
   * <p>
   * Checks whether file contains code. Files which are considered to have no code:
   * </p>
   * <ul>
   * <li>
   * File with no text
   * </li>
   * <li>
   * File with single-line comment(s)
   * </li>
   * <li>
   * File with a multi line comment(s).
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name="NoCodeInFile"/&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <p>
   * Content of the files:
   * </p>
   * <pre>
   * // single-line comment // violation
   * </pre>
   * <pre>
   * /* // violation
   *  block comment
   * *&#47;
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code nocode.in.file}
   * </li>
   * </ul>
   *
   * @since 8.33
   */
  @StatelessCheck
  public class NoCodeInFileCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY_NO_CODE = "nocode.in.file";
  
      /** Line number used to log violation when no AST nodes are present in file. */
      private static final int DEFAULT_LINE_NUMBER = 1;
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return CommonUtil.EMPTY_INT_ARRAY;
      }
  
      @Override
      public void finishTree(DetailAST ast) {
          if (ast == null) {
              log(DEFAULT_LINE_NUMBER, MSG_KEY_NO_CODE);
          }
      }
  }
  