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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) 2001-2024 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   * <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   * <p>
43   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
44   * </p>
45   *
46   * <p>
47   * Violation Message Keys:
48   * </p>
49   * <ul>
50   * <li>
51   * {@code multiple.variable.declarations}
52   * </li>
53   * <li>
54   * {@code multiple.variable.declarations.comma}
55   * </li>
56   * </ul>
57   *
58   * @since 3.4
59   */
60  @StatelessCheck
61  public class MultipleVariableDeclarationsCheck extends AbstractCheck {
62  
63      /**
64       * A key is pointing to the warning message text in "messages.properties"
65       * file.
66       */
67      public static final String MSG_MULTIPLE = "multiple.variable.declarations";
68  
69      /**
70       * A key is pointing to the warning message text in "messages.properties"
71       * file.
72       */
73      public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma";
74  
75      @Override
76      public int[] getAcceptableTokens() {
77          return getRequiredTokens();
78      }
79  
80      @Override
81      public int[] getDefaultTokens() {
82          return getRequiredTokens();
83      }
84  
85      @Override
86      public int[] getRequiredTokens() {
87          return new int[] {TokenTypes.VARIABLE_DEF};
88      }
89  
90      @Override
91      public void visitToken(DetailAST ast) {
92          DetailAST nextNode = ast.getNextSibling();
93  
94          if (nextNode != null) {
95              final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA;
96  
97              if (isCommaSeparated
98                  || nextNode.getType() == TokenTypes.SEMI) {
99                  nextNode = nextNode.getNextSibling();
100             }
101 
102             if (nextNode != null
103                     && nextNode.getType() == TokenTypes.VARIABLE_DEF) {
104                 final DetailAST firstNode = CheckUtil.getFirstNode(ast);
105                 if (isCommaSeparated) {
106                     // Check if the multiple variable declarations are in a
107                     // for loop initializer. If they are, then no warning
108                     // should be displayed. Declaring multiple variables in
109                     // a for loop initializer is a good way to minimize
110                     // variable scope. Refer Feature Request Id - 2895985
111                     // for more details
112                     if (ast.getParent().getType() != TokenTypes.FOR_INIT) {
113                         log(firstNode, MSG_MULTIPLE_COMMA);
114                     }
115                 }
116                 else {
117                     final DetailAST lastNode = getLastNode(ast);
118                     final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode);
119 
120                     if (TokenUtil.areOnSameLine(firstNextNode, lastNode)) {
121                         log(firstNode, MSG_MULTIPLE);
122                     }
123                 }
124             }
125         }
126     }
127 
128     /**
129      * Finds sub-node for given node maximum (line, column) pair.
130      *
131      * @param node the root of tree for search.
132      * @return sub-node with maximum (line, column) pair.
133      */
134     private static DetailAST getLastNode(final DetailAST node) {
135         DetailAST currentNode = node;
136         final DetailAST child = node.getLastChild();
137         if (child != null) {
138             currentNode = getLastNode(child);
139         }
140 
141         return currentNode;
142     }
143 
144 }