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 com.puppycrawl.tools.checkstyle.api.AbstractCheck;
023import com.puppycrawl.tools.checkstyle.api.DetailAST;
024import com.puppycrawl.tools.checkstyle.api.TokenTypes;
025
026/**
027 * <p>
028 * Checks for overly complicated boolean expressions. Currently finds code like
029 * {@code if (b == true)}, {@code b || true}, {@code !false},
030 * etc.
031 * </p>
032 * <p>
033 * Rationale: Complex boolean logic makes code hard to understand and maintain.
034 * </p>
035 * <p>
036 * An example of how to configure the check is:
037 * </p>
038 * <pre>
039 * &lt;module name="SimplifyBooleanExpression"/&gt;
040 * </pre>
041 * @author lkuehne
042 */
043public class SimplifyBooleanExpressionCheck
044        extends AbstractCheck {
045
046    /**
047     * A key is pointing to the warning message text in "messages.properties"
048     * file.
049     */
050    public static final String MSG_KEY = "simplify.expression";
051
052    @Override
053    public int[] getDefaultTokens() {
054        return getAcceptableTokens();
055    }
056
057    @Override
058    public int[] getAcceptableTokens() {
059        return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE};
060    }
061
062    @Override
063    public int[] getRequiredTokens() {
064        return getAcceptableTokens();
065    }
066
067    @Override
068    public void visitToken(DetailAST ast) {
069        final DetailAST parent = ast.getParent();
070        switch (parent.getType()) {
071            case TokenTypes.NOT_EQUAL:
072            case TokenTypes.EQUAL:
073            case TokenTypes.LNOT:
074            case TokenTypes.LOR:
075            case TokenTypes.LAND:
076                log(parent.getLineNo(), parent.getColumnNo(),
077                    MSG_KEY);
078                break;
079            default:
080                break;
081        }
082    }
083}