001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 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.coding;
021
022import com.puppycrawl.tools.checkstyle.StatelessCheck;
023import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
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 that enum definition does not contain a trailing comma.
031 *  Rationale: JLS allows trailing commas in arrays and enumerations, but does not allow
032 *  them in other locations. To unify the coding style, the use of trailing commas should
033 *  be prohibited.
034 * </div>
035 * <pre>
036 * enum Foo1 {
037 *   FOO,
038 *   BAR;
039 * }
040 * </pre>
041 *
042 * <p>
043 *  The check demands that there should not be any comma after last constant in
044 *  enum definition.
045 * </p>
046 * <pre>
047 * enum Foo1 {
048 *   FOO,
049 *   BAR, // violation
050 * }
051 * </pre>
052 *
053 * <p>
054 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
055 * </p>
056 *
057 * <p>
058 * Violation Message Keys:
059 * </p>
060 * <ul>
061 * <li>
062 * {@code no.enum.trailing.comma}
063 * </li>
064 * </ul>
065 *
066 * @since 8.29
067 */
068@StatelessCheck
069public class NoEnumTrailingCommaCheck extends AbstractCheck {
070
071    /**
072     * A key is pointing to the warning message text in "messages.properties"
073     * file.
074     */
075    public static final String MSG_KEY = "no.enum.trailing.comma";
076
077    @Override
078    public int[] getDefaultTokens() {
079        return getRequiredTokens();
080    }
081
082    @Override
083    public int[] getAcceptableTokens() {
084        return getRequiredTokens();
085    }
086
087    @Override
088    public int[] getRequiredTokens() {
089        return new int[] {TokenTypes.ENUM_DEF};
090    }
091
092    @Override
093    public void visitToken(DetailAST detailAST) {
094        final DetailAST enumBlock = detailAST.findFirstToken(TokenTypes.OBJBLOCK);
095        TokenUtil.findFirstTokenByPredicate(enumBlock,
096            node -> TokenUtil.isOfType(node, TokenTypes.SEMI, TokenTypes.RCURLY))
097            .map(DetailAST::getPreviousSibling)
098            .filter(token -> token.getType() == TokenTypes.COMMA)
099            .ifPresent(comma -> log(comma, MSG_KEY));
100    }
101}