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 }