001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2023 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
031 * </p>
032 * <p>
033 * To configure the check:
034 * </p>
035 * <pre>
036 * &lt;module name=&quot;EmptyStatement&quot;/&gt;
037 * </pre>
038 * <p>
039 * Example:
040 * </p>
041 * <pre>
042 * public void foo() {
043 *   int i = 5;
044 *   if (i &gt; 3); // violation, ";" right after if statement
045 *     i++;
046 *   for (i = 0; i &lt; 5; i++); // violation
047 *     i++;
048 *   while (i &gt; 10) // OK
049 *     i++;
050 * }
051 * </pre>
052 * <p>
053 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
054 * </p>
055 * <p>
056 * Violation Message Keys:
057 * </p>
058 * <ul>
059 * <li>
060 * {@code empty.statement}
061 * </li>
062 * </ul>
063 *
064 * @since 3.1
065 */
066@StatelessCheck
067public class EmptyStatementCheck extends AbstractCheck {
068
069    /**
070     * A key is pointing to the warning message text in "messages.properties"
071     * file.
072     */
073    public static final String MSG_KEY = "empty.statement";
074
075    @Override
076    public int[] getDefaultTokens() {
077        return getRequiredTokens();
078    }
079
080    @Override
081    public int[] getAcceptableTokens() {
082        return getRequiredTokens();
083    }
084
085    @Override
086    public int[] getRequiredTokens() {
087        return new int[] {TokenTypes.EMPTY_STAT};
088    }
089
090    @Override
091    public void visitToken(DetailAST ast) {
092        log(ast, MSG_KEY);
093    }
094
095}