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1   ///////////////////////////////////////////////////////////////////////////////////////////////
2   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3   // Copyright (C) 2001-2025 the original author or authors.
4   //
5   // This library is free software; you can redistribute it and/or
6   // modify it under the terms of the GNU Lesser General Public
7   // License as published by the Free Software Foundation; either
8   // version 2.1 of the License, or (at your option) any later version.
9   //
10  // This library is distributed in the hope that it will be useful,
11  // but WITHOUT ANY WARRANTY; without even the implied warranty of
12  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13  // Lesser General Public License for more details.
14  //
15  // You should have received a copy of the GNU Lesser General Public
16  // License along with this library; if not, write to the Free Software
17  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18  ///////////////////////////////////////////////////////////////////////////////////////////////
19  
20  package com.puppycrawl.tools.checkstyle.checks.coding;
21  
22  import com.puppycrawl.tools.checkstyle.StatelessCheck;
23  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
24  import com.puppycrawl.tools.checkstyle.api.DetailAST;
25  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
26  import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
27  
28  /**
29   * <div>
30   * Checks for over-complicated boolean expressions. Currently, it finds code like
31   * {@code if (b == true)}, {@code b || true}, {@code !false},
32   * {@code boolean a = q > 12 ? true : false},
33   * etc.
34   * </div>
35   *
36   * <p>
37   * Rationale: Complex boolean logic makes code hard to understand and maintain.
38   * </p>
39   *
40   * @since 3.0
41   */
42  @StatelessCheck
43  public class SimplifyBooleanExpressionCheck
44          extends AbstractCheck {
45  
46      /**
47       * A key is pointing to the warning message text in "messages.properties"
48       * file.
49       */
50      public static final String MSG_KEY = "simplify.expression";
51  
52      @Override
53      public int[] getDefaultTokens() {
54          return getRequiredTokens();
55      }
56  
57      @Override
58      public int[] getAcceptableTokens() {
59          return getRequiredTokens();
60      }
61  
62      @Override
63      public int[] getRequiredTokens() {
64          return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE};
65      }
66  
67      @Override
68      public void visitToken(DetailAST ast) {
69          final DetailAST parent = ast.getParent();
70          switch (parent.getType()) {
71              case TokenTypes.NOT_EQUAL,
72                   TokenTypes.EQUAL,
73                   TokenTypes.LNOT,
74                   TokenTypes.LOR,
75                   TokenTypes.LAND -> log(parent, MSG_KEY);
76  
77              case TokenTypes.QUESTION -> {
78                  final DetailAST nextSibling = ast.getNextSibling();
79                  if (TokenUtil.isBooleanLiteralType(parent.getFirstChild().getType())
80                          || nextSibling != null && nextSibling.getNextSibling() != null
81                          && TokenUtil.isBooleanLiteralType(
82                          nextSibling.getNextSibling().getType())) {
83                      log(parent, MSG_KEY);
84                  }
85              }
86  
87              default -> {
88                  // do nothing
89              }
90          }
91      }
92  
93  }