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.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;
026
027/**
028 * <div>
029 * Checks if unnecessary semicolon is in enum definitions.
030 * Semicolon is not needed if enum body contains only enum constants.
031 * </div>
032 *
033 * @since 8.22
034 */
035@StatelessCheck
036public final class UnnecessarySemicolonInEnumerationCheck extends AbstractCheck {
037
038    /**
039     * A key is pointing to the warning message text in "messages.properties"
040     * file.
041     */
042    public static final String MSG_SEMI = "unnecessary.semicolon";
043
044    /**
045     * Creates a new {@code UnnecessarySemicolonInEnumerationCheck} instance.
046     */
047    public UnnecessarySemicolonInEnumerationCheck() {
048        // no code by default
049    }
050
051    @Override
052    public int[] getDefaultTokens() {
053        return getRequiredTokens();
054    }
055
056    @Override
057    public int[] getAcceptableTokens() {
058        return getRequiredTokens();
059    }
060
061    @Override
062    public int[] getRequiredTokens() {
063        return new int[] {
064            TokenTypes.ENUM_DEF,
065        };
066    }
067
068    @Override
069    public void visitToken(DetailAST ast) {
070        final DetailAST enumBlock = ast.findFirstToken(TokenTypes.OBJBLOCK);
071        final boolean hasMembers = hasMembersAfterConstants(enumBlock);
072        DetailAST sibling = enumBlock.getFirstChild();
073        while (sibling != null) {
074            if (sibling.getType() == TokenTypes.SEMI
075                    && (!hasMembers || isPrecededBySemi(sibling))) {
076                log(sibling, MSG_SEMI);
077            }
078            sibling = sibling.getNextSibling();
079        }
080    }
081
082    /**
083     * Checks if enum body contains any member (method, constructor, field, etc.)
084     * in addition to enum constants and semicolons.
085     *
086     * @param enumBlock the enum body to check
087     * @return true if enum body has members, false if it only has constants and semicolons.
088     */
089    private static boolean hasMembersAfterConstants(DetailAST enumBlock) {
090        boolean result = false;
091        DetailAST sibling = enumBlock.getFirstChild();
092        while (sibling != null) {
093            final int type = sibling.getType();
094            if (type != TokenTypes.LCURLY
095                    && type != TokenTypes.RCURLY
096                    && type != TokenTypes.ENUM_CONSTANT_DEF
097                    && type != TokenTypes.SEMI
098                    && type != TokenTypes.COMMA) {
099                result = true;
100                break;
101            }
102            sibling = sibling.getNextSibling();
103        }
104        return result;
105    }
106
107    /**
108     * Checks if semicolon is immediately preceded by another semicolon,
109     * making it a redundant duplicate.
110     *
111     * @param ast semicolon to check
112     * @return true if previous sibling is also a semicolon, false otherwise.
113     */
114    private static boolean isPrecededBySemi(DetailAST ast) {
115        final DetailAST prev = ast.getPreviousSibling();
116        return prev.getType() == TokenTypes.SEMI;
117    }
118
119}