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.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 import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
27
28 /**
29 * <div>
30 * Checks that each top-level class, interface, enum
31 * or annotation resides in a source file of its own.
32 * Official description of a 'top-level' term:
33 * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-7.html#jls-7.6">
34 * 7.6. Top Level Type Declarations</a>. If file doesn't contain
35 * public class, interface, enum or annotation, top-level type is the first type in file.
36 * </div>
37 *
38 * @since 5.8
39 */
40 @StatelessCheck
41 public class OneTopLevelClassCheck extends AbstractCheck {
42
43 /**
44 * A key is pointing to the warning message text in "messages.properties"
45 * file.
46 */
47 public static final String MSG_KEY = "one.top.level.class";
48
49 @Override
50 public int[] getDefaultTokens() {
51 return getRequiredTokens();
52 }
53
54 @Override
55 public int[] getAcceptableTokens() {
56 return getRequiredTokens();
57 }
58
59 @Override
60 public int[] getRequiredTokens() {
61 return new int[] {
62 TokenTypes.COMPILATION_UNIT,
63 };
64 }
65
66 @Override
67 public void visitToken(DetailAST compilationUnit) {
68 DetailAST currentNode = compilationUnit.getFirstChild();
69
70 boolean publicTypeFound = false;
71 DetailAST firstType = null;
72
73 while (currentNode != null) {
74 if (isTypeDef(currentNode)) {
75 if (isPublic(currentNode)) {
76 // log the first type later
77 publicTypeFound = true;
78 }
79 if (firstType == null) {
80 // first type is set aside
81 firstType = currentNode;
82 }
83 else if (!isPublic(currentNode)) {
84 // extra non-public type, log immediately
85 final String typeName = currentNode
86 .findFirstToken(TokenTypes.IDENT).getText();
87 log(currentNode, MSG_KEY, typeName);
88 }
89 }
90 currentNode = currentNode.getNextSibling();
91 }
92
93 // if there was a public type and first type is non-public, log it
94 if (publicTypeFound && !isPublic(firstType)) {
95 final String typeName = firstType
96 .findFirstToken(TokenTypes.IDENT).getText();
97 log(firstType, MSG_KEY, typeName);
98 }
99 }
100
101 /**
102 * Checks if an AST node is a type definition.
103 *
104 * @param node AST node to check.
105 * @return true if the node is a type (class, enum, interface, annotation) definition.
106 */
107 private static boolean isTypeDef(DetailAST node) {
108 return TokenUtil.isTypeDeclaration(node.getType());
109 }
110
111 /**
112 * Checks if a type is public.
113 *
114 * @param typeDef type definition node.
115 * @return true if a type has a public access level modifier.
116 */
117 private static boolean isPublic(DetailAST typeDef) {
118 final DetailAST modifiers =
119 typeDef.findFirstToken(TokenTypes.MODIFIERS);
120 return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null;
121 }
122
123 }