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 import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
27
28 /**
29 * <p>
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 * </p>
37 * <p>
38 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
39 * </p>
40 * <p>
41 * Violation Message Keys:
42 * </p>
43 * <ul>
44 * <li>
45 * {@code one.top.level.class}
46 * </li>
47 * </ul>
48 *
49 * @since 5.8
50 */
51 @StatelessCheck
52 public class OneTopLevelClassCheck extends AbstractCheck {
53
54 /**
55 * A key is pointing to the warning message text in "messages.properties"
56 * file.
57 */
58 public static final String MSG_KEY = "one.top.level.class";
59
60 @Override
61 public int[] getDefaultTokens() {
62 return getRequiredTokens();
63 }
64
65 @Override
66 public int[] getAcceptableTokens() {
67 return getRequiredTokens();
68 }
69
70 @Override
71 public int[] getRequiredTokens() {
72 return new int[] {
73 TokenTypes.COMPILATION_UNIT,
74 };
75 }
76
77 @Override
78 public void visitToken(DetailAST compilationUnit) {
79 DetailAST currentNode = compilationUnit.getFirstChild();
80
81 boolean publicTypeFound = false;
82 DetailAST firstType = null;
83
84 while (currentNode != null) {
85 if (isTypeDef(currentNode)) {
86 if (isPublic(currentNode)) {
87 // log the first type later
88 publicTypeFound = true;
89 }
90 if (firstType == null) {
91 // first type is set aside
92 firstType = currentNode;
93 }
94 else if (!isPublic(currentNode)) {
95 // extra non-public type, log immediately
96 final String typeName = currentNode
97 .findFirstToken(TokenTypes.IDENT).getText();
98 log(currentNode, MSG_KEY, typeName);
99 }
100 }
101 currentNode = currentNode.getNextSibling();
102 }
103
104 // if there was a public type and first type is non-public, log it
105 if (publicTypeFound && !isPublic(firstType)) {
106 final String typeName = firstType
107 .findFirstToken(TokenTypes.IDENT).getText();
108 log(firstType, MSG_KEY, typeName);
109 }
110 }
111
112 /**
113 * Checks if an AST node is a type definition.
114 *
115 * @param node AST node to check.
116 * @return true if the node is a type (class, enum, interface, annotation) definition.
117 */
118 private static boolean isTypeDef(DetailAST node) {
119 return TokenUtil.isTypeDeclaration(node.getType());
120 }
121
122 /**
123 * Checks if a type is public.
124 *
125 * @param typeDef type definition node.
126 * @return true if a type has a public access level modifier.
127 */
128 private static boolean isPublic(DetailAST typeDef) {
129 final DetailAST modifiers =
130 typeDef.findFirstToken(TokenTypes.MODIFIERS);
131 return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null;
132 }
133
134 }