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