001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2015 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 antlr.collections.AST;
023
024import com.puppycrawl.tools.checkstyle.api.Check;
025import com.puppycrawl.tools.checkstyle.api.DetailAST;
026import com.puppycrawl.tools.checkstyle.api.TokenTypes;
027
028/**
029 * <p>Checks that string literals are not used with
030 * {@code ==} or {@code &#33;=}.
031 * </p>
032 * <p>
033 * Rationale: Novice Java programmers often use code like
034 * {@code if (x == &quot;something&quot;)} when they mean
035 * {@code if (&quot;something&quot;.equals(x))}.
036 * </p>
037 *
038 * @author Lars K&uuml;hne
039 */
040public class StringLiteralEqualityCheck extends Check {
041
042    /**
043     * A key is pointing to the warning message text in "messages.properties"
044     * file.
045     */
046    public static final String MSG_KEY = "string.literal.equality";
047
048    @Override
049    public int[] getDefaultTokens() {
050        return getAcceptableTokens();
051    }
052
053    @Override
054    public int[] getAcceptableTokens() {
055        return new int[] {TokenTypes.EQUAL, TokenTypes.NOT_EQUAL};
056    }
057
058    @Override
059    public int[] getRequiredTokens() {
060        return getAcceptableTokens();
061    }
062
063    @Override
064    public void visitToken(DetailAST ast) {
065        // no need to check for nulls here, == and != always have two children
066        final AST firstChild = ast.getFirstChild();
067        final AST secondChild = firstChild.getNextSibling();
068
069        if (firstChild.getType() == TokenTypes.STRING_LITERAL
070                || secondChild.getType() == TokenTypes.STRING_LITERAL) {
071            log(ast.getLineNo(), ast.getColumnNo(),
072                    MSG_KEY, ast.getText());
073        }
074    }
075}