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