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.coding;
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.CheckUtil;
27 import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
28
29 /**
30 * <p>
31 * Checks that each variable declaration is in its own statement
32 * and on its own line.
33 * </p>
34 * <p>
35 * Rationale: <a
36 * href="https://checkstyle.org/styleguides/sun-code-conventions-19990420/CodeConventions.doc5.html#a2992">
37 * the Java code conventions chapter 6.1</a> recommends that
38 * declarations should be one per line/statement.
39 * </p>
40 * <p>
41 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
42 * </p>
43 * <p>
44 * Violation Message Keys:
45 * </p>
46 * <ul>
47 * <li>
48 * {@code multiple.variable.declarations}
49 * </li>
50 * <li>
51 * {@code multiple.variable.declarations.comma}
52 * </li>
53 * </ul>
54 *
55 * @since 3.4
56 */
57 @StatelessCheck
58 public class MultipleVariableDeclarationsCheck extends AbstractCheck {
59
60 /**
61 * A key is pointing to the warning message text in "messages.properties"
62 * file.
63 */
64 public static final String MSG_MULTIPLE = "multiple.variable.declarations";
65
66 /**
67 * A key is pointing to the warning message text in "messages.properties"
68 * file.
69 */
70 public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma";
71
72 @Override
73 public int[] getAcceptableTokens() {
74 return getRequiredTokens();
75 }
76
77 @Override
78 public int[] getDefaultTokens() {
79 return getRequiredTokens();
80 }
81
82 @Override
83 public int[] getRequiredTokens() {
84 return new int[] {TokenTypes.VARIABLE_DEF};
85 }
86
87 @Override
88 public void visitToken(DetailAST ast) {
89 DetailAST nextNode = ast.getNextSibling();
90
91 if (nextNode != null) {
92 final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA;
93
94 if (isCommaSeparated
95 || nextNode.getType() == TokenTypes.SEMI) {
96 nextNode = nextNode.getNextSibling();
97 }
98
99 if (nextNode != null
100 && nextNode.getType() == TokenTypes.VARIABLE_DEF) {
101 final DetailAST firstNode = CheckUtil.getFirstNode(ast);
102 if (isCommaSeparated) {
103 // Check if the multiple variable declarations are in a
104 // for loop initializer. If they are, then no warning
105 // should be displayed. Declaring multiple variables in
106 // a for loop initializer is a good way to minimize
107 // variable scope. Refer Feature Request Id - 2895985
108 // for more details
109 if (ast.getParent().getType() != TokenTypes.FOR_INIT) {
110 log(firstNode, MSG_MULTIPLE_COMMA);
111 }
112 }
113 else {
114 final DetailAST lastNode = getLastNode(ast);
115 final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode);
116
117 if (TokenUtil.areOnSameLine(firstNextNode, lastNode)) {
118 log(firstNode, MSG_MULTIPLE);
119 }
120 }
121 }
122 }
123 }
124
125 /**
126 * Finds sub-node for given node maximum (line, column) pair.
127 *
128 * @param node the root of tree for search.
129 * @return sub-node with maximum (line, column) pair.
130 */
131 private static DetailAST getLastNode(final DetailAST node) {
132 DetailAST currentNode = node;
133 final DetailAST child = node.getLastChild();
134 if (child != null) {
135 currentNode = getLastNode(child);
136 }
137
138 return currentNode;
139 }
140
141 }