001/////////////////////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code and other text files for adherence to a set of rules. 003// Copyright (C) 2001-2024 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.design; 021 022import com.puppycrawl.tools.checkstyle.StatelessCheck; 023import com.puppycrawl.tools.checkstyle.api.AbstractCheck; 024import com.puppycrawl.tools.checkstyle.api.DetailAST; 025import com.puppycrawl.tools.checkstyle.api.TokenTypes; 026 027/** 028 * <div> 029 * Checks that sealed classes and interfaces have a permits list. 030 * </div> 031 * 032 * <p> 033 * Rationale: When a permits clause is omitted from a sealed class, 034 * any class within the same compilation unit can extend it. This differs 035 * from other sealed classes where permitted subclasses are explicitly 036 * declared, making them readily visible to the reader. Without a permits 037 * clause, identifying potential subclasses requires searching the entire 038 * compilation unit, which can be challenging, especially in large files 039 * with complex class hierarchies. 040 * </p> 041 * 042 * <p> 043 * See the <a href="https://docs.oracle.com/javase/specs/jls/se22/html/jls-13.html#jls-13.4.2"> 044 * Java Language Specification</a> for more information about sealed classes. 045 * </p> 046 * 047 * <p> 048 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker} 049 * </p> 050 * 051 * <p> 052 * Violation Message Keys: 053 * </p> 054 * <ul> 055 * <li> 056 * {@code sealed.should.have.permits} 057 * </li> 058 * </ul> 059 * 060 * @since 10.18.0 061 */ 062 063@StatelessCheck 064public class SealedShouldHavePermitsListCheck extends AbstractCheck { 065 066 /** 067 * A key is pointing to the warning message text in "messages.properties" 068 * file. 069 */ 070 public static final String MSG_KEY = "sealed.should.have.permits"; 071 072 @Override 073 public int[] getDefaultTokens() { 074 return getRequiredTokens(); 075 } 076 077 @Override 078 public int[] getAcceptableTokens() { 079 return getRequiredTokens(); 080 } 081 082 @Override 083 public int[] getRequiredTokens() { 084 return new int[] { 085 TokenTypes.CLASS_DEF, 086 TokenTypes.INTERFACE_DEF, 087 }; 088 } 089 090 @Override 091 public void visitToken(DetailAST ast) { 092 final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS); 093 final boolean isSealed = modifiers.findFirstToken(TokenTypes.LITERAL_SEALED) != null; 094 final boolean hasPermitsList = ast.findFirstToken(TokenTypes.PERMITS_CLAUSE) != null; 095 096 if (isSealed && !hasPermitsList) { 097 log(ast, MSG_KEY); 098 } 099 } 100}