1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2024 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.design;
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.TokenTypes;
26
27 /**
28 * <p>
29 * Checks that sealed classes and interfaces have a permits list.
30 * </p>
31 * <p>
32 * Rationale: When a permits clause is omitted from a sealed class,
33 * any class within the same compilation unit can extend it. This differs
34 * from other sealed classes where permitted subclasses are explicitly
35 * declared, making them readily visible to the reader. Without a permits
36 * clause, identifying potential subclasses requires searching the entire
37 * compilation unit, which can be challenging, especially in large files
38 * with complex class hierarchies.
39 * </p>
40 * <p>
41 * See the <a href="https://docs.oracle.com/javase/specs/jls/se22/html/jls-13.html#jls-13.4.2">
42 * Java Language Specification</a> for more information about sealed classes.
43 * </p>
44 * <p>
45 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
46 * </p>
47 * <p>
48 * Violation Message Keys:
49 * </p>
50 * <ul>
51 * <li>
52 * {@code sealed.should.have.permits}
53 * </li>
54 * </ul>
55 *
56 * @since 10.18.0
57 */
58
59 @StatelessCheck
60 public class SealedShouldHavePermitsListCheck extends AbstractCheck {
61
62 /**
63 * A key is pointing to the warning message text in "messages.properties"
64 * file.
65 */
66 public static final String MSG_KEY = "sealed.should.have.permits";
67
68 @Override
69 public int[] getDefaultTokens() {
70 return getRequiredTokens();
71 }
72
73 @Override
74 public int[] getAcceptableTokens() {
75 return getRequiredTokens();
76 }
77
78 @Override
79 public int[] getRequiredTokens() {
80 return new int[] {
81 TokenTypes.CLASS_DEF,
82 TokenTypes.INTERFACE_DEF,
83 };
84 }
85
86 @Override
87 public void visitToken(DetailAST ast) {
88 final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
89 final boolean isSealed = modifiers.findFirstToken(TokenTypes.LITERAL_SEALED) != null;
90 final boolean hasPermitsList = ast.findFirstToken(TokenTypes.PERMITS_CLAUSE) != null;
91
92 if (isSealed && !hasPermitsList) {
93 log(ast, MSG_KEY);
94 }
95 }
96 }