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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  
27  /**
28   * <p>
29   * Checks that array initialization do not contain a trailing comma.
30   * Rationale: JLS allows trailing commas in arrays and enumerations, but does not allow
31   * them in other locations. To unify the coding style, the use of trailing commas should
32   * be prohibited.
33   * </p>
34   * <pre>
35   * int[] foo = new int[] {
36   *   1,
37   *   2
38   * };
39   * </pre>
40   * <p>
41   * The check demands that there should not be any comma after the last element of an array.
42   * </p>
43   * <pre>
44   * String[] foo = new String[] {
45   *   "FOO",
46   *   "BAR", //violation
47   * }
48   * </pre>
49   * <p>
50   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
51   * </p>
52   * <p>
53   * Violation Message Keys:
54   * </p>
55   * <ul>
56   * <li>
57   * {@code no.array.trailing.comma}
58   * </li>
59   * </ul>
60   *
61   * @since 8.28
62   */
63  @StatelessCheck
64  public class NoArrayTrailingCommaCheck extends AbstractCheck {
65  
66      /**
67       * A key is pointing to the warning message text in "messages.properties"
68       * file.
69       */
70      public static final String MSG_KEY = "no.array.trailing.comma";
71  
72      @Override
73      public int[] getDefaultTokens() {
74          return getRequiredTokens();
75      }
76  
77      @Override
78      public int[] getAcceptableTokens() {
79          return getRequiredTokens();
80      }
81  
82      @Override
83      public int[] getRequiredTokens() {
84          return new int[] {TokenTypes.ARRAY_INIT};
85      }
86  
87      @Override
88      public void visitToken(DetailAST arrayInit) {
89          final DetailAST rcurly = arrayInit.findFirstToken(TokenTypes.RCURLY);
90          final DetailAST previousSibling = rcurly.getPreviousSibling();
91          if (previousSibling != null && previousSibling.getType() == TokenTypes.COMMA) {
92              log(previousSibling, MSG_KEY);
93          }
94      }
95  }