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