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 * <p>
041 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
042 * </p>
043 *
044 * <p>
045 * Violation Message Keys:
046 * </p>
047 * <ul>
048 * <li>
049 * {@code simplify.expression}
050 * </li>
051 * </ul>
052 *
053 * @since 3.0
054 */
055@StatelessCheck
056public class SimplifyBooleanExpressionCheck
057        extends AbstractCheck {
058
059    /**
060     * A key is pointing to the warning message text in "messages.properties"
061     * file.
062     */
063    public static final String MSG_KEY = "simplify.expression";
064
065    @Override
066    public int[] getDefaultTokens() {
067        return getRequiredTokens();
068    }
069
070    @Override
071    public int[] getAcceptableTokens() {
072        return getRequiredTokens();
073    }
074
075    @Override
076    public int[] getRequiredTokens() {
077        return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE};
078    }
079
080    @Override
081    public void visitToken(DetailAST ast) {
082        final DetailAST parent = ast.getParent();
083        switch (parent.getType()) {
084            case TokenTypes.NOT_EQUAL:
085            case TokenTypes.EQUAL:
086            case TokenTypes.LNOT:
087            case TokenTypes.LOR:
088            case TokenTypes.LAND:
089                log(parent, MSG_KEY);
090                break;
091            case TokenTypes.QUESTION:
092                final DetailAST nextSibling = ast.getNextSibling();
093                if (TokenUtil.isBooleanLiteralType(parent.getFirstChild().getType())
094                        || nextSibling != null && nextSibling.getNextSibling() != null
095                        && TokenUtil.isBooleanLiteralType(
096                        nextSibling.getNextSibling().getType())) {
097                    log(parent, MSG_KEY);
098                }
099                break;
100            default:
101                break;
102        }
103    }
104
105}