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
27 /**
28 * <div>
29 * Check that the {@code default} is after all the cases in a {@code switch} statement.
30 * </div>
31 *
32 * <p>
33 * Rationale: Java allows {@code default} anywhere within the
34 * {@code switch} statement. But it is more readable if it comes after the last {@code case}.
35 * </p>
36 *
37 * @since 3.4
38 */
39 @StatelessCheck
40 public class DefaultComesLastCheck extends AbstractCheck {
41
42 /**
43 * A key is pointing to the warning message text in "messages.properties" file.
44 */
45 public static final String MSG_KEY = "default.comes.last";
46
47 /**
48 * A key is pointing to the warning message text in "messages.properties" file.
49 */
50 public static final String MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE =
51 "default.comes.last.in.casegroup";
52
53 /** Control whether to allow {@code default} along with {@code case} if they are not last. */
54 private boolean skipIfLastAndSharedWithCase;
55
56 /**
57 * Creates a new {@code DefaultComesLastCheck} instance.
58 */
59 public DefaultComesLastCheck() {
60 // no code by default
61 }
62
63 @Override
64 public int[] getAcceptableTokens() {
65 return getRequiredTokens();
66 }
67
68 @Override
69 public int[] getDefaultTokens() {
70 return getRequiredTokens();
71 }
72
73 @Override
74 public int[] getRequiredTokens() {
75 return new int[] {
76 TokenTypes.LITERAL_DEFAULT,
77 };
78 }
79
80 /**
81 * Setter to control whether to allow {@code default} along with
82 * {@code case} if they are not last.
83 *
84 * @param newValue whether to ignore checking.
85 * @since 7.7
86 */
87 public void setSkipIfLastAndSharedWithCase(boolean newValue) {
88 skipIfLastAndSharedWithCase = newValue;
89 }
90
91 @Override
92 public void visitToken(DetailAST ast) {
93 final DetailAST defaultGroupAST = ast.getParent();
94
95 // Switch rules are not subject to fall through.
96 final boolean isSwitchRule = defaultGroupAST.getType() == TokenTypes.SWITCH_RULE;
97
98 if (skipIfLastAndSharedWithCase && !isSwitchRule) {
99 if (isNextSiblingOf(ast, TokenTypes.LITERAL_CASE)) {
100 log(ast, MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE);
101 }
102 else if (ast.getPreviousSibling() == null
103 && isNextSiblingOf(defaultGroupAST,
104 TokenTypes.CASE_GROUP)) {
105 log(ast, MSG_KEY);
106 }
107 }
108 else if (isNextSiblingOf(defaultGroupAST,
109 TokenTypes.CASE_GROUP)
110 || isNextSiblingOf(defaultGroupAST,
111 TokenTypes.SWITCH_RULE)) {
112 log(ast, MSG_KEY);
113 }
114 }
115
116 /**
117 * Return true only if passed tokenType in argument is found or returns false.
118 *
119 * @param ast root node.
120 * @param tokenType tokentype to be processed.
121 * @return true if desired token is found or else false.
122 */
123 private static boolean isNextSiblingOf(DetailAST ast, int tokenType) {
124 return ast.getNextSibling() != null && ast.getNextSibling().getType() == tokenType;
125 }
126
127 }