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 * <p>Example:</p>
049 * <pre>
050 *  public class Test {
051 *
052 *      protected void finalize() throws Throwable { // violation
053 *          try {
054 *             System.out.println("overriding finalize()");
055 *          } catch (Throwable t) {
056 *             throw t;
057 *          } finally {
058 *             super.finalize();
059 *          }
060 *      }
061 *  }
062 * </pre>
063 * <p>
064 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
065 * </p>
066 * <p>
067 * Violation Message Keys:
068 * </p>
069 * <ul>
070 * <li>
071 * {@code avoid.finalizer.method}
072 * </li>
073 * </ul>
074 *
075 * @since 5.0
076 */
077@StatelessCheck
078public class NoFinalizerCheck extends AbstractCheck {
079
080    /**
081     * A key is pointing to the warning message text in "messages.properties"
082     * file.
083     */
084    public static final String MSG_KEY = "avoid.finalizer.method";
085
086    @Override
087    public int[] getDefaultTokens() {
088        return getRequiredTokens();
089    }
090
091    @Override
092    public int[] getAcceptableTokens() {
093        return getRequiredTokens();
094    }
095
096    @Override
097    public int[] getRequiredTokens() {
098        return new int[] {TokenTypes.METHOD_DEF};
099    }
100
101    @Override
102    public void visitToken(DetailAST ast) {
103        final DetailAST mid = ast.findFirstToken(TokenTypes.IDENT);
104        final String name = mid.getText();
105
106        if ("finalize".equals(name)) {
107            final DetailAST params = ast.findFirstToken(TokenTypes.PARAMETERS);
108            final boolean hasEmptyParamList =
109                params.findFirstToken(TokenTypes.PARAMETER_DEF) == null;
110
111            if (hasEmptyParamList) {
112                log(ast, MSG_KEY);
113            }
114        }
115    }
116
117}