001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2020 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 * <p>
029 * Detects empty statements (standalone {@code ";"} semicolon).
030 * Empty statements often introduce bugs that are hard to spot, such as in
031 * </p>
032 * <pre>
033 * if (someCondition);
034 *   doConditionalStuff();
035 * doUnconditionalStuff();
036 * </pre>
037 * <p>
038 * To configure the check:
039 * </p>
040 * <pre>
041 * &lt;module name=&quot;EmptyStatement&quot;/&gt;
042 * </pre>
043 * <p>
044 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
045 * </p>
046 * <p>
047 * Violation Message Keys:
048 * </p>
049 * <ul>
050 * <li>
051 * {@code empty.statement}
052 * </li>
053 * </ul>
054 *
055 * @since 3.1
056 */
057@StatelessCheck
058public class EmptyStatementCheck extends AbstractCheck {
059
060    /**
061     * A key is pointing to the warning message text in "messages.properties"
062     * file.
063     */
064    public static final String MSG_KEY = "empty.statement";
065
066    @Override
067    public int[] getDefaultTokens() {
068        return getRequiredTokens();
069    }
070
071    @Override
072    public int[] getAcceptableTokens() {
073        return getRequiredTokens();
074    }
075
076    @Override
077    public int[] getRequiredTokens() {
078        return new int[] {TokenTypes.EMPTY_STAT};
079    }
080
081    @Override
082    public void visitToken(DetailAST ast) {
083        log(ast, MSG_KEY);
084    }
085
086}