001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2017 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;
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>Checks that string literals are not used with
029 * {@code ==} or {@code &#33;=}.
030 * </p>
031 * <p>
032 * Rationale: Novice Java programmers often use code like
033 * {@code if (x == &quot;something&quot;)} when they mean
034 * {@code if (&quot;something&quot;.equals(x))}.
035 * </p>
036 *
037 * @author Lars K&uuml;hne
038 */
039public class StringLiteralEqualityCheck extends AbstractCheck {
040
041    /**
042     * A key is pointing to the warning message text in "messages.properties"
043     * file.
044     */
045    public static final String MSG_KEY = "string.literal.equality";
046
047    @Override
048    public int[] getDefaultTokens() {
049        return getAcceptableTokens();
050    }
051
052    @Override
053    public int[] getAcceptableTokens() {
054        return new int[] {TokenTypes.EQUAL, TokenTypes.NOT_EQUAL};
055    }
056
057    @Override
058    public int[] getRequiredTokens() {
059        return getAcceptableTokens();
060    }
061
062    @Override
063    public void visitToken(DetailAST ast) {
064        // no need to check for nulls here, == and != always have two children
065        final AST firstChild = ast.getFirstChild();
066        final AST secondChild = firstChild.getNextSibling();
067
068        if (firstChild.getType() == TokenTypes.STRING_LITERAL
069                || secondChild.getType() == TokenTypes.STRING_LITERAL) {
070            log(ast.getLineNo(), ast.getColumnNo(),
071                    MSG_KEY, ast.getText());
072        }
073    }
074}