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 }