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.modifier;
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.Scope;
26 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
27 import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
28
29 /**
30 * <div>
31 * Checks for implicit modifiers on nested types in classes and records.
32 * </div>
33 *
34 * <p>
35 * This check is effectively the opposite of
36 * <a href="https://checkstyle.org/checks/modifier/redundantmodifier.html">
37 * RedundantModifier</a>.
38 * It checks the modifiers on nested types in classes and records, ensuring that certain modifiers
39 * are explicitly specified even though they are actually redundant.
40 * </p>
41 *
42 * <p>
43 * Nested enums, interfaces, and records within a class are always {@code static} and as such the
44 * compiler does not require the {@code static} modifier. This check provides the ability to enforce
45 * that the {@code static} modifier is explicitly coded and not implicitly added by the compiler.
46 * </p>
47 * <div class="wrapper"><pre class="prettyprint"><code class="language-java">
48 * public final class Person {
49 * enum Age { // violation
50 * CHILD, ADULT
51 * }
52 * }
53 * </code></pre></div>
54 *
55 * <p>
56 * Rationale for this check: Nested enums, interfaces, and records are treated differently from
57 * nested classes as they are only allowed to be {@code static}. Developers should not need to
58 * remember this rule, and this check provides the means to enforce that the modifier is coded
59 * explicitly.
60 * </p>
61 *
62 * @since 8.16
63 */
64 @StatelessCheck
65 public class ClassMemberImpliedModifierCheck
66 extends AbstractCheck {
67
68 /**
69 * A key is pointing to the warning message text in "messages.properties" file.
70 */
71 public static final String MSG_KEY = "class.implied.modifier";
72
73 /** Name for 'static' keyword. */
74 private static final String STATIC_KEYWORD = "static";
75
76 /**
77 * Control whether to enforce that {@code static} is explicitly coded
78 * on nested enums in classes and records.
79 */
80 private boolean violateImpliedStaticOnNestedEnum = true;
81
82 /**
83 * Control whether to enforce that {@code static} is explicitly coded
84 * on nested interfaces in classes and records.
85 */
86 private boolean violateImpliedStaticOnNestedInterface = true;
87
88 /**
89 * Control whether to enforce that {@code static} is explicitly coded
90 * on nested records in classes and records.
91 */
92 private boolean violateImpliedStaticOnNestedRecord = true;
93
94 /**
95 * Setter to control whether to enforce that {@code static} is explicitly coded
96 * on nested enums in classes and records.
97 *
98 * @param violateImplied
99 * True to perform the check, false to turn the check off.
100 * @since 8.16
101 */
102 public void setViolateImpliedStaticOnNestedEnum(boolean violateImplied) {
103 violateImpliedStaticOnNestedEnum = violateImplied;
104 }
105
106 /**
107 * Setter to control whether to enforce that {@code static} is explicitly coded
108 * on nested interfaces in classes and records.
109 *
110 * @param violateImplied
111 * True to perform the check, false to turn the check off.
112 * @since 8.16
113 */
114 public void setViolateImpliedStaticOnNestedInterface(boolean violateImplied) {
115 violateImpliedStaticOnNestedInterface = violateImplied;
116 }
117
118 /**
119 * Setter to control whether to enforce that {@code static} is explicitly coded
120 * on nested records in classes and records.
121 *
122 * @param violateImplied
123 * True to perform the check, false to turn the check off.
124 * @since 8.36
125 */
126 public void setViolateImpliedStaticOnNestedRecord(boolean violateImplied) {
127 violateImpliedStaticOnNestedRecord = violateImplied;
128 }
129
130 @Override
131 public int[] getDefaultTokens() {
132 return getAcceptableTokens();
133 }
134
135 @Override
136 public int[] getRequiredTokens() {
137 return getAcceptableTokens();
138 }
139
140 @Override
141 public int[] getAcceptableTokens() {
142 return new int[] {
143 TokenTypes.INTERFACE_DEF,
144 TokenTypes.ENUM_DEF,
145 TokenTypes.RECORD_DEF,
146 };
147 }
148
149 @Override
150 public void visitToken(DetailAST ast) {
151 if (isInTypeBlock(ast)) {
152 final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
153 switch (ast.getType()) {
154 case TokenTypes.ENUM_DEF -> {
155 if (violateImpliedStaticOnNestedEnum
156 && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
157 log(ast, MSG_KEY, STATIC_KEYWORD);
158 }
159 }
160
161 case TokenTypes.INTERFACE_DEF -> {
162 if (violateImpliedStaticOnNestedInterface
163 && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
164 log(ast, MSG_KEY, STATIC_KEYWORD);
165 }
166 }
167
168 case TokenTypes.RECORD_DEF -> {
169 if (violateImpliedStaticOnNestedRecord
170 && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
171 log(ast, MSG_KEY, STATIC_KEYWORD);
172 }
173 }
174
175 default -> throw new IllegalStateException(ast.toString());
176 }
177 }
178 }
179
180 /**
181 * Checks if ast is in a class, enum, anon class or record block.
182 *
183 * @param ast the current ast
184 * @return true if ast is in a class, enum, anon class or record
185 */
186 private static boolean isInTypeBlock(DetailAST ast) {
187 return ScopeUtil.isInScope(ast, Scope.ANONINNER)
188 || ScopeUtil.isInClassBlock(ast)
189 || ScopeUtil.isInEnumBlock(ast)
190 || ScopeUtil.isInRecordBlock(ast);
191 }
192
193 }