001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2024 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;
026import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
027
028/**
029 * <p>
030 * Checks for over-complicated boolean expressions. Currently, it finds code like
031 * {@code if (b == true)}, {@code b || true}, {@code !false},
032 * {@code boolean a = q > 12 ? true : false},
033 * etc.
034 * </p>
035 * <p>
036 * Rationale: Complex boolean logic makes code hard to understand and maintain.
037 * </p>
038 * <p>
039 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
040 * </p>
041 * <p>
042 * Violation Message Keys:
043 * </p>
044 * <ul>
045 * <li>
046 * {@code simplify.expression}
047 * </li>
048 * </ul>
049 *
050 * @since 3.0
051 */
052@StatelessCheck
053public class SimplifyBooleanExpressionCheck
054        extends AbstractCheck {
055
056    /**
057     * A key is pointing to the warning message text in "messages.properties"
058     * file.
059     */
060    public static final String MSG_KEY = "simplify.expression";
061
062    @Override
063    public int[] getDefaultTokens() {
064        return getRequiredTokens();
065    }
066
067    @Override
068    public int[] getAcceptableTokens() {
069        return getRequiredTokens();
070    }
071
072    @Override
073    public int[] getRequiredTokens() {
074        return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE};
075    }
076
077    @Override
078    public void visitToken(DetailAST ast) {
079        final DetailAST parent = ast.getParent();
080        switch (parent.getType()) {
081            case TokenTypes.NOT_EQUAL:
082            case TokenTypes.EQUAL:
083            case TokenTypes.LNOT:
084            case TokenTypes.LOR:
085            case TokenTypes.LAND:
086                log(parent, MSG_KEY);
087                break;
088            case TokenTypes.QUESTION:
089                final DetailAST nextSibling = ast.getNextSibling();
090                if (TokenUtil.isBooleanLiteralType(parent.getFirstChild().getType())
091                        || nextSibling != null && nextSibling.getNextSibling() != null
092                        && TokenUtil.isBooleanLiteralType(
093                        nextSibling.getNextSibling().getType())) {
094                    log(parent, MSG_KEY);
095                }
096                break;
097            default:
098                break;
099        }
100    }
101
102}