001/////////////////////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code and other text files for adherence to a set of rules. 003// Copyright (C) 2001-2022 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 * To configure the check: 040 * </p> 041 * <pre> 042 * <module name="SimplifyBooleanExpression"/> 043 * </pre> 044 * <p>Example:</p> 045 * <pre> 046 * public class Test { 047 * 048 * public void bar() { 049 * 050 * boolean a, b; 051 * Foo c, d, e; 052 * 053 * if (!false) {}; // violation, can be simplified to true 054 * 055 * if (a == true) {}; // violation, can be simplified to a 056 * if (a == b) {}; // OK 057 * if (a == false) {}; // violation, can be simplified to !a 058 * if (!(a != true)) {}; // violation, can be simplified to a 059 * 060 * e = (a || b) ? c : d; // OK 061 * e = (a || false) ? c : d; // violation, can be simplified to a 062 * e = (a && b) ? c : d; // OK 063 * 064 * int s = 12; 065 * boolean m = s > 1 ? true : false; // violation, can be simplified to s > 1 066 * boolean f = c == null ? false : c.someMethod(); // OK 067 * } 068 * 069 * } 070 * </pre> 071 * <p> 072 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker} 073 * </p> 074 * <p> 075 * Violation Message Keys: 076 * </p> 077 * <ul> 078 * <li> 079 * {@code simplify.expression} 080 * </li> 081 * </ul> 082 * 083 * @since 3.0 084 */ 085@StatelessCheck 086public class SimplifyBooleanExpressionCheck 087 extends AbstractCheck { 088 089 /** 090 * A key is pointing to the warning message text in "messages.properties" 091 * file. 092 */ 093 public static final String MSG_KEY = "simplify.expression"; 094 095 @Override 096 public int[] getDefaultTokens() { 097 return getRequiredTokens(); 098 } 099 100 @Override 101 public int[] getAcceptableTokens() { 102 return getRequiredTokens(); 103 } 104 105 @Override 106 public int[] getRequiredTokens() { 107 return new int[] {TokenTypes.LITERAL_TRUE, TokenTypes.LITERAL_FALSE}; 108 } 109 110 @Override 111 public void visitToken(DetailAST ast) { 112 final DetailAST parent = ast.getParent(); 113 switch (parent.getType()) { 114 case TokenTypes.NOT_EQUAL: 115 case TokenTypes.EQUAL: 116 case TokenTypes.LNOT: 117 case TokenTypes.LOR: 118 case TokenTypes.LAND: 119 log(parent, MSG_KEY); 120 break; 121 case TokenTypes.QUESTION: 122 final DetailAST nextSibling = ast.getNextSibling(); 123 if (TokenUtil.isBooleanLiteralType(parent.getFirstChild().getType()) 124 || nextSibling != null 125 && TokenUtil.isBooleanLiteralType( 126 nextSibling.getNextSibling().getType())) { 127 log(parent, MSG_KEY); 128 } 129 break; 130 default: 131 break; 132 } 133 } 134 135}