001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 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 * <div>
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 * </div>
035 *
036 * <p>
037 * Rationale: Complex boolean logic makes code hard to understand and maintain.
038 * </p>
039 *
040 * @since 3.0
041 */
042@StatelessCheck
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 getRequiredTokens();
055    }
056
057    @Override
058    public int[] getAcceptableTokens() {
059        return getRequiredTokens();
060    }
061
062    @Override
063    public int[] getRequiredTokens() {
064        return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE};
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                 TokenTypes.EQUAL,
073                 TokenTypes.LNOT,
074                 TokenTypes.LOR,
075                 TokenTypes.LAND -> log(parent, MSG_KEY);
076
077            case TokenTypes.QUESTION -> {
078                final DetailAST nextSibling = ast.getNextSibling();
079                if (TokenUtil.isBooleanLiteralType(parent.getFirstChild().getType())
080                        || nextSibling != null && nextSibling.getNextSibling() != null
081                        && TokenUtil.isBooleanLiteralType(
082                        nextSibling.getNextSibling().getType())) {
083                    log(parent, MSG_KEY);
084                }
085            }
086
087            default -> {
088                // do nothing
089            }
090        }
091    }
092
093}