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;
  import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
  
  /**
   * <p>
   * Checks for over-complicated boolean expressions. Currently, it finds code like
   * {@code if (b == true)}, {@code b || true}, {@code !false},
   * {@code boolean a = q > 12 ? true : false},
   * etc.
   * </p>
   * <p>
   * Rationale: Complex boolean logic makes code hard to understand and maintain.
   * </p>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name=&quot;SimplifyBooleanExpression&quot;/&gt;
   * </pre>
   * <p>Example:</p>
   * <pre>
   * public class Test {
   *
   *   public void bar() {
   *
   *     boolean a, b;
   *     Foo c, d, e;
   *
   *     if (!false) {};       // violation, can be simplified to true
   *
   *     if (a == true) {};    // violation, can be simplified to a
   *     if (a == b) {};       // OK
   *     if (a == false) {};   // violation, can be simplified to !a
   *     if (!(a != true)) {}; // violation, can be simplified to a
   *
   *     e = (a || b) ? c : d;     // OK
   *     e = (a || false) ? c : d; // violation, can be simplified to a
   *     e = (a &amp;&amp; b) ? c : d;     // OK
   *
   *     int s = 12;
   *     boolean m = s &gt; 1 ? true : false; // violation, can be simplified to s &gt; 1
   *     boolean f = c == null ? false : c.someMethod(); // OK
   *  }
   *
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code simplify.expression}
   * </li>
   * </ul>
   *
   * @since 3.0
   */
  @StatelessCheck
  public class SimplifyBooleanExpressionCheck
          extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "simplify.expression";
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE};
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          final DetailAST parent = ast.getParent();
          switch (parent.getType()) {
              case TokenTypes.NOT_EQUAL:
              case TokenTypes.EQUAL:
              case TokenTypes.LNOT:
              case TokenTypes.LOR:
              case TokenTypes.LAND:
                  log(parent, MSG_KEY);
                  break;
              case TokenTypes.QUESTION:
                  final DetailAST nextSibling = ast.getNextSibling();
                  if (TokenUtil.isBooleanLiteralType(parent.getFirstChild().getType())
                          || nextSibling != null && nextSibling.getNextSibling() != null
                          && TokenUtil.isBooleanLiteralType(
                          nextSibling.getNextSibling().getType())) {
                      log(parent, MSG_KEY);
                  }
                  break;
              default:
                  break;
          }
      }
  
  }
  