001//////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code for adherence to a set of rules. 003// Copyright (C) 2001-2018 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.CheckUtil; 027import com.puppycrawl.tools.checkstyle.utils.ScopeUtil; 028 029/** 030 * <p> 031 * Checks if any class or object member explicitly initialized 032 * to default for its type value ({@code null} for object 033 * references, zero for numeric types and {@code char} 034 * and {@code false} for {@code boolean}. 035 * </p> 036 * <p> 037 * Rationale: each instance variable gets 038 * initialized twice, to the same value. Java 039 * initializes each instance variable to its default 040 * value (0 or null) before performing any 041 * initialization specified in the code. So in this case, 042 * x gets initialized to 0 twice, and bar gets initialized 043 * to null twice. So there is a minor inefficiency. This style of 044 * coding is a hold-over from C/C++ style coding, 045 * and it shows that the developer isn't really confident that 046 * Java really initializes instance variables to default 047 * values. 048 * </p> 049 * 050 */ 051@StatelessCheck 052public class ExplicitInitializationCheck extends AbstractCheck { 053 054 /** 055 * A key is pointing to the warning message text in "messages.properties" 056 * file. 057 */ 058 public static final String MSG_KEY = "explicit.init"; 059 060 /** Whether only explicit initialization made to null should be checked.**/ 061 private boolean onlyObjectReferences; 062 063 @Override 064 public final int[] getDefaultTokens() { 065 return getRequiredTokens(); 066 } 067 068 @Override 069 public final int[] getRequiredTokens() { 070 return new int[] {TokenTypes.VARIABLE_DEF}; 071 } 072 073 @Override 074 public final int[] getAcceptableTokens() { 075 return getRequiredTokens(); 076 } 077 078 /** 079 * Sets whether only explicit initialization made to null should be checked. 080 * @param onlyObjectReferences whether only explicit initialization made to null 081 * should be checked 082 */ 083 public void setOnlyObjectReferences(boolean onlyObjectReferences) { 084 this.onlyObjectReferences = onlyObjectReferences; 085 } 086 087 @Override 088 public void visitToken(DetailAST ast) { 089 if (!isSkipCase(ast)) { 090 final DetailAST assign = ast.findFirstToken(TokenTypes.ASSIGN); 091 final DetailAST exprStart = 092 assign.getFirstChild().getFirstChild(); 093 final DetailAST type = ast.findFirstToken(TokenTypes.TYPE); 094 if (isObjectType(type) 095 && exprStart.getType() == TokenTypes.LITERAL_NULL) { 096 final DetailAST ident = ast.findFirstToken(TokenTypes.IDENT); 097 log(ident, MSG_KEY, ident.getText(), "null"); 098 } 099 if (!onlyObjectReferences) { 100 validateNonObjects(ast); 101 } 102 } 103 } 104 105 /** 106 * Checks for explicit initializations made to 'false', '0' and '\0'. 107 * @param ast token being checked for explicit initializations 108 */ 109 private void validateNonObjects(DetailAST ast) { 110 final DetailAST ident = ast.findFirstToken(TokenTypes.IDENT); 111 final DetailAST assign = ast.findFirstToken(TokenTypes.ASSIGN); 112 final DetailAST exprStart = 113 assign.getFirstChild().getFirstChild(); 114 final DetailAST type = ast.findFirstToken(TokenTypes.TYPE); 115 final int primitiveType = type.getFirstChild().getType(); 116 if (primitiveType == TokenTypes.LITERAL_BOOLEAN 117 && exprStart.getType() == TokenTypes.LITERAL_FALSE) { 118 log(ident, MSG_KEY, ident.getText(), "false"); 119 } 120 if (isNumericType(primitiveType) && isZero(exprStart)) { 121 log(ident, MSG_KEY, ident.getText(), "0"); 122 } 123 if (primitiveType == TokenTypes.LITERAL_CHAR 124 && isZeroChar(exprStart)) { 125 log(ident, MSG_KEY, ident.getText(), "\\0"); 126 } 127 } 128 129 /** 130 * Examine char literal for initializing to default value. 131 * @param exprStart expression 132 * @return true is literal is initialized by zero symbol 133 */ 134 private static boolean isZeroChar(DetailAST exprStart) { 135 return isZero(exprStart) 136 || exprStart.getType() == TokenTypes.CHAR_LITERAL 137 && "'\\0'".equals(exprStart.getText()); 138 } 139 140 /** 141 * Checks for cases that should be skipped: no assignment, local variable, final variables. 142 * @param ast Variable def AST 143 * @return true is that is a case that need to be skipped. 144 */ 145 private static boolean isSkipCase(DetailAST ast) { 146 boolean skipCase = true; 147 148 // do not check local variables and 149 // fields declared in interface/annotations 150 if (!ScopeUtil.isLocalVariableDef(ast) 151 && !ScopeUtil.isInInterfaceOrAnnotationBlock(ast)) { 152 final DetailAST assign = ast.findFirstToken(TokenTypes.ASSIGN); 153 154 if (assign != null) { 155 final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS); 156 skipCase = modifiers.findFirstToken(TokenTypes.FINAL) != null; 157 } 158 } 159 return skipCase; 160 } 161 162 /** 163 * Determines if a given type is an object type. 164 * @param type type to check. 165 * @return true if it is an object type. 166 */ 167 private static boolean isObjectType(DetailAST type) { 168 final int objectType = type.getFirstChild().getType(); 169 return objectType == TokenTypes.IDENT || objectType == TokenTypes.DOT 170 || objectType == TokenTypes.ARRAY_DECLARATOR; 171 } 172 173 /** 174 * Determine if a given type is a numeric type. 175 * @param type code of the type for check. 176 * @return true if it's a numeric type. 177 * @see TokenTypes 178 */ 179 private static boolean isNumericType(int type) { 180 return type == TokenTypes.LITERAL_BYTE 181 || type == TokenTypes.LITERAL_SHORT 182 || type == TokenTypes.LITERAL_INT 183 || type == TokenTypes.LITERAL_FLOAT 184 || type == TokenTypes.LITERAL_LONG 185 || type == TokenTypes.LITERAL_DOUBLE; 186 } 187 188 /** 189 * Checks if given node contains numeric constant for zero. 190 * 191 * @param expr node to check. 192 * @return true if given node contains numeric constant for zero. 193 */ 194 private static boolean isZero(DetailAST expr) { 195 final int type = expr.getType(); 196 final boolean isZero; 197 switch (type) { 198 case TokenTypes.NUM_FLOAT: 199 case TokenTypes.NUM_DOUBLE: 200 case TokenTypes.NUM_INT: 201 case TokenTypes.NUM_LONG: 202 final String text = expr.getText(); 203 isZero = Double.compare(CheckUtil.parseDouble(text, type), 0.0) == 0; 204 break; 205 default: 206 isZero = false; 207 } 208 return isZero; 209 } 210 211}