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.naming;
21
22 import java.util.Objects;
23
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 lambda parameter names.
31 * </div>
32 *
33 * @since 8.11
34 */
35 public class LambdaParameterNameCheck extends AbstractNameCheck {
36
37 /**
38 * A key is pointing to the warning message text in "messages.properties"
39 * file.
40 */
41 public static final String MSG_INVALID_PATTERN = "name.invalidPattern";
42
43 /** Creates new instance of {@code LambdaParameterNameCheck}. */
44 public LambdaParameterNameCheck() {
45 super("^([a-z][a-zA-Z0-9]*|_)$", MSG_INVALID_PATTERN);
46 }
47
48 @Override
49 public int[] getDefaultTokens() {
50 return getRequiredTokens();
51 }
52
53 @Override
54 public int[] getAcceptableTokens() {
55 return getRequiredTokens();
56 }
57
58 @Override
59 public int[] getRequiredTokens() {
60 return new int[] {
61 TokenTypes.LAMBDA,
62 };
63 }
64
65 @Override
66 public void visitToken(DetailAST ast) {
67 if (Objects.nonNull(ast.findFirstToken(TokenTypes.PARAMETERS))) {
68 final DetailAST parametersNode = ast.findFirstToken(TokenTypes.PARAMETERS);
69 TokenUtil.forEachChild(parametersNode, TokenTypes.PARAMETER_DEF, super::visitToken);
70 }
71 else if (!isSwitchRuleLambda(ast)) {
72 super.visitToken(ast);
73 }
74 }
75
76 @Override
77 protected boolean mustCheckName(DetailAST ast) {
78 return true;
79 }
80
81 /**
82 * Checks whether a lambda token represents a switch rule arrow.
83 * Switch rule arrows have no children, while lambda expressions do.
84 *
85 * @param lambda the lambda AST node
86 * @return true if the token represents a switch rule arrow
87 */
88 private static boolean isSwitchRuleLambda(DetailAST lambda) {
89 return !lambda.hasChildren();
90 }
91
92 }