1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2026 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.TokenUtil;
27
28 /**
29 * <div>
30 * Checks that array initialization contains a trailing comma.
31 * </div>
32 *
33 * {@snippet lang="text" :
34 * int[] a = new int[]
35 * {
36 * 1,
37 * 2,
38 * 3,
39 * };
40 * }
41 *
42 * <p>
43 * By default, the check demands a comma at the end if neither left nor right curly braces
44 * are on the same line as the last element of the array.
45 * </p>
46 * {@snippet lang="text" :
47 * return new int[] { 0 };
48 * return new int[] { 0
49 * };
50 * return new int[] {
51 * 0 };
52 * }
53 *
54 * <p>
55 * Rationale: Putting this comma in makes it easier to change the
56 * order of the elements or add new elements on the end. Main benefit of a trailing
57 * comma is that when you add new entry to an array, no surrounding lines are changed.
58 * </p>
59 * {@snippet lang="text" :
60 * {
61 * 100000000000000000000,
62 * 200000000000000000000, // OK
63 * }
64 *
65 * {
66 * 100000000000000000000,
67 * 200000000000000000000,
68 * 300000000000000000000, // Just this line added, no other changes
69 * }
70 * }
71 *
72 * <p>
73 * If closing brace is on the same line as trailing comma, this benefit is gone
74 * (as the check does not demand a certain location of curly braces the following
75 * two cases will not produce a violation):
76 * </p>
77 * {@snippet lang="text" :
78 * {100000000000000000000,
79 * 200000000000000000000,} // Trailing comma not needed, line needs to be modified anyway
80 *
81 * {100000000000000000000,
82 * 200000000000000000000, // Modified line
83 * 300000000000000000000,} // Added line
84 * }
85 *
86 * <p>
87 * If opening brace is on the same line as trailing comma there's also (more arguable) problem:
88 * </p>
89 * {@snippet lang="text" :
90 * {100000000000000000000, // Line cannot be just duplicated to slightly modify entry
91 * }
92 *
93 * {100000000000000000000,
94 * 100000000000000000001, // More work needed to duplicate
95 * }
96 * }
97 *
98 * @since 3.2
99 */
100 @StatelessCheck
101 public class ArrayTrailingCommaCheck extends AbstractCheck {
102
103 /**
104 * A key is pointing to the warning message text in "messages.properties"
105 * file.
106 */
107 public static final String MSG_KEY = "array.trailing.comma";
108
109 /**
110 * Control whether to always check for a trailing comma, even when an array is inline.
111 */
112 private boolean alwaysDemandTrailingComma;
113
114 /**
115 * Creates a new {@code ArrayTrailingCommaCheck} instance.
116 */
117 public ArrayTrailingCommaCheck() {
118 // no code by default
119 }
120
121 /**
122 * Setter to control whether to always check for a trailing comma, even when an array is inline.
123 *
124 * @param alwaysDemandTrailingComma whether to always check for a trailing comma.
125 * @since 8.33
126 */
127 public void setAlwaysDemandTrailingComma(boolean alwaysDemandTrailingComma) {
128 this.alwaysDemandTrailingComma = alwaysDemandTrailingComma;
129 }
130
131 @Override
132 public int[] getDefaultTokens() {
133 return getRequiredTokens();
134 }
135
136 @Override
137 public int[] getAcceptableTokens() {
138 return getRequiredTokens();
139 }
140
141 @Override
142 public int[] getRequiredTokens() {
143 return new int[] {TokenTypes.ARRAY_INIT};
144 }
145
146 @Override
147 public void visitToken(DetailAST arrayInit) {
148 final DetailAST rcurly = arrayInit.findFirstToken(TokenTypes.RCURLY);
149 final DetailAST previousSibling = rcurly.getPreviousSibling();
150
151 if (arrayInit.getChildCount() != 1
152 && (alwaysDemandTrailingComma
153 || !TokenUtil.areOnSameLine(rcurly, previousSibling)
154 && !TokenUtil.areOnSameLine(arrayInit, previousSibling))
155 && previousSibling.getType() != TokenTypes.COMMA) {
156 log(previousSibling, MSG_KEY);
157 }
158 }
159
160 }