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 * <p>
39 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
40 * </p>
41 *
42 * <p>
43 * Violation Message Keys:
44 * </p>
45 * <ul>
46 * <li>
47 * {@code one.top.level.class}
48 * </li>
49 * </ul>
50 *
51 * @since 5.8
52 */
53 @StatelessCheck
54 public class OneTopLevelClassCheck extends AbstractCheck {
55
56 /**
57 * A key is pointing to the warning message text in "messages.properties"
58 * file.
59 */
60 public static final String MSG_KEY = "one.top.level.class";
61
62 @Override
63 public int[] getDefaultTokens() {
64 return getRequiredTokens();
65 }
66
67 @Override
68 public int[] getAcceptableTokens() {
69 return getRequiredTokens();
70 }
71
72 @Override
73 public int[] getRequiredTokens() {
74 return new int[] {
75 TokenTypes.COMPILATION_UNIT,
76 };
77 }
78
79 @Override
80 public void visitToken(DetailAST compilationUnit) {
81 DetailAST currentNode = compilationUnit.getFirstChild();
82
83 boolean publicTypeFound = false;
84 DetailAST firstType = null;
85
86 while (currentNode != null) {
87 if (isTypeDef(currentNode)) {
88 if (isPublic(currentNode)) {
89 // log the first type later
90 publicTypeFound = true;
91 }
92 if (firstType == null) {
93 // first type is set aside
94 firstType = currentNode;
95 }
96 else if (!isPublic(currentNode)) {
97 // extra non-public type, log immediately
98 final String typeName = currentNode
99 .findFirstToken(TokenTypes.IDENT).getText();
100 log(currentNode, MSG_KEY, typeName);
101 }
102 }
103 currentNode = currentNode.getNextSibling();
104 }
105
106 // if there was a public type and first type is non-public, log it
107 if (publicTypeFound && !isPublic(firstType)) {
108 final String typeName = firstType
109 .findFirstToken(TokenTypes.IDENT).getText();
110 log(firstType, MSG_KEY, typeName);
111 }
112 }
113
114 /**
115 * Checks if an AST node is a type definition.
116 *
117 * @param node AST node to check.
118 * @return true if the node is a type (class, enum, interface, annotation) definition.
119 */
120 private static boolean isTypeDef(DetailAST node) {
121 return TokenUtil.isTypeDeclaration(node.getType());
122 }
123
124 /**
125 * Checks if a type is public.
126 *
127 * @param typeDef type definition node.
128 * @return true if a type has a public access level modifier.
129 */
130 private static boolean isPublic(DetailAST typeDef) {
131 final DetailAST modifiers =
132 typeDef.findFirstToken(TokenTypes.MODIFIERS);
133 return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null;
134 }
135
136 }