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.CheckUtil; 027import com.puppycrawl.tools.checkstyle.utils.TokenUtil; 028 029/** 030 * <div> 031 * Checks that each variable declaration is in its own statement 032 * and on its own line. 033 * </div> 034 * 035 * <p> 036 * Rationale: <a 037 * href="https://checkstyle.org/styleguides/sun-code-conventions-19990420/CodeConventions.doc5.html#a2992"> 038 * the Java code conventions chapter 6.1</a> recommends that 039 * declarations should be one per line/statement. 040 * </p> 041 * 042 * <p> 043 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker} 044 * </p> 045 * 046 * <p> 047 * Violation Message Keys: 048 * </p> 049 * <ul> 050 * <li> 051 * {@code multiple.variable.declarations} 052 * </li> 053 * <li> 054 * {@code multiple.variable.declarations.comma} 055 * </li> 056 * </ul> 057 * 058 * @since 3.4 059 */ 060@StatelessCheck 061public class MultipleVariableDeclarationsCheck extends AbstractCheck { 062 063 /** 064 * A key is pointing to the warning message text in "messages.properties" 065 * file. 066 */ 067 public static final String MSG_MULTIPLE = "multiple.variable.declarations"; 068 069 /** 070 * A key is pointing to the warning message text in "messages.properties" 071 * file. 072 */ 073 public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma"; 074 075 @Override 076 public int[] getAcceptableTokens() { 077 return getRequiredTokens(); 078 } 079 080 @Override 081 public int[] getDefaultTokens() { 082 return getRequiredTokens(); 083 } 084 085 @Override 086 public int[] getRequiredTokens() { 087 return new int[] {TokenTypes.VARIABLE_DEF}; 088 } 089 090 @Override 091 public void visitToken(DetailAST ast) { 092 DetailAST nextNode = ast.getNextSibling(); 093 094 if (nextNode != null) { 095 final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA; 096 097 if (isCommaSeparated 098 || nextNode.getType() == TokenTypes.SEMI) { 099 nextNode = nextNode.getNextSibling(); 100 } 101 102 if (nextNode != null 103 && nextNode.getType() == TokenTypes.VARIABLE_DEF) { 104 final DetailAST firstNode = CheckUtil.getFirstNode(ast); 105 if (isCommaSeparated) { 106 // Check if the multiple variable declarations are in a 107 // for loop initializer. If they are, then no warning 108 // should be displayed. Declaring multiple variables in 109 // a for loop initializer is a good way to minimize 110 // variable scope. Refer Feature Request Id - 2895985 111 // for more details 112 if (ast.getParent().getType() != TokenTypes.FOR_INIT) { 113 log(firstNode, MSG_MULTIPLE_COMMA); 114 } 115 } 116 else { 117 final DetailAST lastNode = getLastNode(ast); 118 final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode); 119 120 if (TokenUtil.areOnSameLine(firstNextNode, lastNode)) { 121 log(firstNode, MSG_MULTIPLE); 122 } 123 } 124 } 125 } 126 } 127 128 /** 129 * Finds sub-node for given node maximum (line, column) pair. 130 * 131 * @param node the root of tree for search. 132 * @return sub-node with maximum (line, column) pair. 133 */ 134 private static DetailAST getLastNode(final DetailAST node) { 135 DetailAST currentNode = node; 136 final DetailAST child = node.getLastChild(); 137 if (child != null) { 138 currentNode = getLastNode(child); 139 } 140 141 return currentNode; 142 } 143 144}