001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2014  Oliver Burn
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////////////////////////////////////////////////////////////////////////////////
019package com.puppycrawl.tools.checkstyle.checks.coding;
020
021import com.google.common.collect.Sets;
022import com.puppycrawl.tools.checkstyle.api.Check;
023import com.puppycrawl.tools.checkstyle.api.DetailAST;
024import com.puppycrawl.tools.checkstyle.api.FullIdent;
025import com.puppycrawl.tools.checkstyle.api.TokenTypes;
026import com.puppycrawl.tools.checkstyle.checks.CheckUtils;
027import java.util.Set;
028
029/**
030 * <p>Checks that if a class defines a covariant method equals,
031 * then it defines method equals(java.lang.Object).
032 * Inspired by findbugs,
033 * http://findbugs.sourceforge.net/bugDescriptions.html#EQ_SELF_NO_OBJECT
034 * </p>
035 * <p>
036 * An example of how to configure the check is:
037 * </p>
038 * <pre>
039 * &lt;module name="CovariantEquals"/&gt;
040 * </pre>
041 * @author Rick Giles
042 * @version 1.0
043 */
044public class CovariantEqualsCheck extends Check
045{
046    /** Set of equals method definitions */
047    private final Set<DetailAST> equalsMethods = Sets.newHashSet();
048
049    @Override
050    public int[] getDefaultTokens()
051    {
052        return new int[] {TokenTypes.CLASS_DEF, TokenTypes.LITERAL_NEW, };
053    }
054
055    @Override
056    public int[] getRequiredTokens()
057    {
058        return getDefaultTokens();
059    }
060
061    @Override
062    public void visitToken(DetailAST ast)
063    {
064        equalsMethods.clear();
065        boolean hasEqualsObject = false;
066
067        // examine method definitions for equals methods
068        final DetailAST objBlock = ast.findFirstToken(TokenTypes.OBJBLOCK);
069        if (objBlock != null) {
070            DetailAST child = objBlock.getFirstChild();
071            while (child != null) {
072                if (child.getType() == TokenTypes.METHOD_DEF
073                        && CheckUtils.isEqualsMethod(child))
074                {
075                    if (hasObjectParameter(child)) {
076                        hasEqualsObject = true;
077                    }
078                    else {
079                        equalsMethods.add(child);
080                    }
081                }
082                child = child.getNextSibling();
083            }
084
085            // report equals method definitions
086            if (!hasEqualsObject) {
087                for (DetailAST equalsAST : equalsMethods) {
088                    final DetailAST nameNode = equalsAST
089                            .findFirstToken(TokenTypes.IDENT);
090                    log(nameNode.getLineNo(), nameNode.getColumnNo(),
091                            "covariant.equals");
092                }
093            }
094        }
095    }
096
097    /**
098     * Tests whether a method definition AST has exactly one
099     * parameter of type Object.
100     * @param ast the method definition AST to test.
101     * Precondition: ast is a TokenTypes.METHOD_DEF node.
102     * @return true if ast has exactly one parameter of type Object.
103     */
104    private boolean hasObjectParameter(DetailAST ast)
105    {
106        // one parameter?
107        final DetailAST paramsNode = ast.findFirstToken(TokenTypes.PARAMETERS);
108        if (paramsNode.getChildCount() != 1) {
109            return false;
110        }
111
112        // parameter type "Object"?
113        final DetailAST paramNode =
114            paramsNode.findFirstToken(TokenTypes.PARAMETER_DEF);
115        final DetailAST typeNode = paramNode.findFirstToken(TokenTypes.TYPE);
116        final FullIdent fullIdent = FullIdent.createFullIdentBelow(typeNode);
117        final String name = fullIdent.getText();
118        return ("Object".equals(name) || "java.lang.Object".equals(name));
119    }
120}