001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2026 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018///////////////////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks.naming;
021
022import java.util.Objects;
023
024import com.puppycrawl.tools.checkstyle.api.DetailAST;
025import com.puppycrawl.tools.checkstyle.api.TokenTypes;
026import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
027
028/**
029 * <div>
030 * Checks lambda parameter names.
031 * </div>
032 *
033 * @since 8.11
034 */
035public class LambdaParameterNameCheck extends AbstractNameCheck {
036
037    /**
038     * A key is pointing to the warning message text in "messages.properties"
039     * file.
040     */
041    public static final String MSG_INVALID_PATTERN = "name.invalidPattern";
042
043    /** Creates new instance of {@code LambdaParameterNameCheck}. */
044    public LambdaParameterNameCheck() {
045        super("^([a-z][a-zA-Z0-9]*|_)$", MSG_INVALID_PATTERN);
046    }
047
048    @Override
049    public int[] getDefaultTokens() {
050        return getRequiredTokens();
051    }
052
053    @Override
054    public int[] getAcceptableTokens() {
055        return getRequiredTokens();
056    }
057
058    @Override
059    public int[] getRequiredTokens() {
060        return new int[] {
061            TokenTypes.LAMBDA,
062        };
063    }
064
065    @Override
066    public void visitToken(DetailAST ast) {
067        if (Objects.nonNull(ast.findFirstToken(TokenTypes.PARAMETERS))) {
068            final DetailAST parametersNode = ast.findFirstToken(TokenTypes.PARAMETERS);
069            TokenUtil.forEachChild(parametersNode, TokenTypes.PARAMETER_DEF, super::visitToken);
070        }
071        else if (!isSwitchRuleLambda(ast)) {
072            super.visitToken(ast);
073        }
074    }
075
076    @Override
077    protected boolean mustCheckName(DetailAST ast) {
078        return true;
079    }
080
081    /**
082     * Checks whether a lambda token represents a switch rule arrow.
083     * Switch rule arrows have no children, while lambda expressions do.
084     *
085     * @param lambda the lambda AST node
086     * @return true if the token represents a switch rule arrow
087     */
088    private static boolean isSwitchRuleLambda(DetailAST lambda) {
089        return !lambda.hasChildren();
090    }
091
092}