001/////////////////////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code and other text files for adherence to a set of rules. 003// Copyright (C) 2001-2025 the original author or authors. 004// 005// This library is free software; you can redistribute it and/or 006// modify it under the terms of the GNU Lesser General Public 007// License as published by the Free Software Foundation; either 008// version 2.1 of the License, or (at your option) any later version. 009// 010// This library is distributed in the hope that it will be useful, 011// but WITHOUT ANY WARRANTY; without even the implied warranty of 012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 013// Lesser General Public License for more details. 014// 015// You should have received a copy of the GNU Lesser General Public 016// License along with this library; if not, write to the Free Software 017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 018/////////////////////////////////////////////////////////////////////////////////////////////// 019 020package com.puppycrawl.tools.checkstyle.checks; 021 022import java.util.Optional; 023import java.util.Set; 024import java.util.regex.Pattern; 025 026import com.puppycrawl.tools.checkstyle.FileStatefulCheck; 027import com.puppycrawl.tools.checkstyle.api.AbstractCheck; 028import com.puppycrawl.tools.checkstyle.api.DetailAST; 029import com.puppycrawl.tools.checkstyle.api.FullIdent; 030import com.puppycrawl.tools.checkstyle.api.TokenTypes; 031 032/** 033 * <div> 034 * Detects uncommented {@code main} methods. 035 * </div> 036 * 037 * <p> 038 * Rationale: A {@code main} method is often used for debugging purposes. 039 * When debugging is finished, developers often forget to remove the method, 040 * which changes the API and increases the size of the resulting class or JAR file. 041 * Except for the real program entry points, all {@code main} methods 042 * should be removed or commented out of the sources. 043 * </p> 044 * 045 * @since 3.2 046 */ 047@FileStatefulCheck 048public class UncommentedMainCheck 049 extends AbstractCheck { 050 051 /** 052 * A key is pointing to the warning message text in "messages.properties" 053 * file. 054 */ 055 public static final String MSG_KEY = "uncommented.main"; 056 057 /** Set of possible String array types. */ 058 private static final Set<String> STRING_PARAMETER_NAMES = Set.of( 059 String[].class.getCanonicalName(), 060 String.class.getCanonicalName(), 061 String[].class.getSimpleName(), 062 String.class.getSimpleName() 063 ); 064 065 /** 066 * Specify pattern for qualified names of classes which are allowed to 067 * have a {@code main} method. 068 */ 069 private Pattern excludedClasses = Pattern.compile("^$"); 070 /** Current class name. */ 071 private String currentClass; 072 /** Current package. */ 073 private FullIdent packageName; 074 /** Class definition depth. */ 075 private int classDepth; 076 077 /** 078 * Setter to specify pattern for qualified names of classes which are allowed 079 * to have a {@code main} method. 080 * 081 * @param excludedClasses a pattern 082 * @since 3.2 083 */ 084 public void setExcludedClasses(Pattern excludedClasses) { 085 this.excludedClasses = excludedClasses; 086 } 087 088 @Override 089 public int[] getAcceptableTokens() { 090 return getRequiredTokens(); 091 } 092 093 @Override 094 public int[] getDefaultTokens() { 095 return getRequiredTokens(); 096 } 097 098 @Override 099 public int[] getRequiredTokens() { 100 return new int[] { 101 TokenTypes.METHOD_DEF, 102 TokenTypes.CLASS_DEF, 103 TokenTypes.PACKAGE_DEF, 104 TokenTypes.RECORD_DEF, 105 }; 106 } 107 108 @Override 109 public void beginTree(DetailAST rootAST) { 110 packageName = FullIdent.createFullIdent(null); 111 classDepth = 0; 112 } 113 114 @Override 115 public void leaveToken(DetailAST ast) { 116 if (ast.getType() == TokenTypes.CLASS_DEF) { 117 classDepth--; 118 } 119 } 120 121 @Override 122 public void visitToken(DetailAST ast) { 123 switch (ast.getType()) { 124 case TokenTypes.PACKAGE_DEF -> visitPackageDef(ast); 125 case TokenTypes.RECORD_DEF, TokenTypes.CLASS_DEF -> visitClassOrRecordDef(ast); 126 case TokenTypes.METHOD_DEF -> visitMethodDef(ast); 127 default -> throw new IllegalStateException(ast.toString()); 128 } 129 } 130 131 /** 132 * Sets current package. 133 * 134 * @param packageDef node for package definition 135 */ 136 private void visitPackageDef(DetailAST packageDef) { 137 packageName = FullIdent.createFullIdent(packageDef.getLastChild() 138 .getPreviousSibling()); 139 } 140 141 /** 142 * If not inner class then change current class name. 143 * 144 * @param classOrRecordDef node for class or record definition 145 */ 146 private void visitClassOrRecordDef(DetailAST classOrRecordDef) { 147 // we are not use inner classes because they can not 148 // have static methods 149 if (classDepth == 0) { 150 final DetailAST ident = classOrRecordDef.findFirstToken(TokenTypes.IDENT); 151 currentClass = packageName.getText() + "." + ident.getText(); 152 classDepth++; 153 } 154 } 155 156 /** 157 * Checks method definition if this is 158 * {@code public static void main(String[])}. 159 * 160 * @param method method definition node 161 */ 162 private void visitMethodDef(DetailAST method) { 163 if (classDepth == 1 164 // method not in inner class or in interface definition 165 && checkClassName() 166 && checkName(method) 167 && checkModifiers(method) 168 && checkType(method) 169 && checkParams(method)) { 170 log(method, MSG_KEY); 171 } 172 } 173 174 /** 175 * Checks that current class is not excluded. 176 * 177 * @return true if check passed, false otherwise 178 */ 179 private boolean checkClassName() { 180 return !excludedClasses.matcher(currentClass).find(); 181 } 182 183 /** 184 * Checks that method name is @quot;main@quot;. 185 * 186 * @param method the METHOD_DEF node 187 * @return true if check passed, false otherwise 188 */ 189 private static boolean checkName(DetailAST method) { 190 final DetailAST ident = method.findFirstToken(TokenTypes.IDENT); 191 return "main".equals(ident.getText()); 192 } 193 194 /** 195 * Checks that method has final and static modifiers. 196 * 197 * @param method the METHOD_DEF node 198 * @return true if check passed, false otherwise 199 */ 200 private static boolean checkModifiers(DetailAST method) { 201 final DetailAST modifiers = 202 method.findFirstToken(TokenTypes.MODIFIERS); 203 204 return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null 205 && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) != null; 206 } 207 208 /** 209 * Checks that return type is {@code void}. 210 * 211 * @param method the METHOD_DEF node 212 * @return true if check passed, false otherwise 213 */ 214 private static boolean checkType(DetailAST method) { 215 final DetailAST type = 216 method.findFirstToken(TokenTypes.TYPE).getFirstChild(); 217 return type.getType() == TokenTypes.LITERAL_VOID; 218 } 219 220 /** 221 * Checks that method has only {@code String[]} or only {@code String...} param. 222 * 223 * @param method the METHOD_DEF node 224 * @return true if check passed, false otherwise 225 */ 226 private static boolean checkParams(DetailAST method) { 227 boolean checkPassed = false; 228 final DetailAST params = method.findFirstToken(TokenTypes.PARAMETERS); 229 230 if (params.getChildCount() == 1) { 231 final DetailAST parameterType = params.getFirstChild().findFirstToken(TokenTypes.TYPE); 232 final boolean isArrayDeclaration = 233 parameterType.findFirstToken(TokenTypes.ARRAY_DECLARATOR) != null; 234 final Optional<DetailAST> varargs = Optional.ofNullable( 235 params.getFirstChild().findFirstToken(TokenTypes.ELLIPSIS)); 236 237 if (isArrayDeclaration || varargs.isPresent()) { 238 checkPassed = isStringType(parameterType.getFirstChild()); 239 } 240 } 241 return checkPassed; 242 } 243 244 /** 245 * Whether the type is java.lang.String. 246 * 247 * @param typeAst the type to check. 248 * @return true, if the type is java.lang.String. 249 */ 250 private static boolean isStringType(DetailAST typeAst) { 251 final FullIdent type = FullIdent.createFullIdent(typeAst); 252 return STRING_PARAMETER_NAMES.contains(type.getText()); 253 } 254 255}