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 * Checks that there is no method {@code finalize} with zero parameters.
030 * </p>
031 * <p>
032 * See
033 * <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#finalize()">
034 * Object.finalize()</a>
035 * </p>
036 * <p>
037 * Rationale: Finalizers are unpredictable, often dangerous, and generally unnecessary.
038 * Their use can cause erratic behavior, poor performance, and portability problems.
039 * For more information for the finalize method and its issues, see Effective Java:
040 * Programming Language Guide Third Edition by Joshua Bloch, &#167;8.
041 * </p>
042 * <p>
043 * To configure the check:
044 * </p>
045 * <pre>
046 * &lt;module name=&quot;NoFinalizer&quot;/&gt;
047 * </pre>
048 *
049 * @since 5.0
050 */
051@StatelessCheck
052public class NoFinalizerCheck extends AbstractCheck {
053
054    /**
055     * A key is pointing to the warning message text in "messages.properties"
056     * file.
057     */
058    public static final String MSG_KEY = "avoid.finalizer.method";
059
060    @Override
061    public int[] getDefaultTokens() {
062        return getRequiredTokens();
063    }
064
065    @Override
066    public int[] getAcceptableTokens() {
067        return getRequiredTokens();
068    }
069
070    @Override
071    public int[] getRequiredTokens() {
072        return new int[] {TokenTypes.METHOD_DEF};
073    }
074
075    @Override
076    public void visitToken(DetailAST aAST) {
077        final DetailAST mid = aAST.findFirstToken(TokenTypes.IDENT);
078        final String name = mid.getText();
079
080        if ("finalize".equals(name)) {
081            final DetailAST params = aAST.findFirstToken(TokenTypes.PARAMETERS);
082            final boolean hasEmptyParamList =
083                params.findFirstToken(TokenTypes.PARAMETER_DEF) == null;
084
085            if (hasEmptyParamList) {
086                log(aAST.getLineNo(), MSG_KEY);
087            }
088        }
089    }
090
091}