1 /////////////////////////////////////////////////////////////////////////////////////////////// 2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules. 3 // Copyright (C) 2001-2024 the original author or authors. 4 // 5 // This library is free software; you can redistribute it and/or 6 // modify it under the terms of the GNU Lesser General Public 7 // License as published by the Free Software Foundation; either 8 // version 2.1 of the License, or (at your option) any later version. 9 // 10 // This library is distributed in the hope that it will be useful, 11 // but WITHOUT ANY WARRANTY; without even the implied warranty of 12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 // Lesser General Public License for more details. 14 // 15 // You should have received a copy of the GNU Lesser General Public 16 // License along with this library; if not, write to the Free Software 17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 18 /////////////////////////////////////////////////////////////////////////////////////////////// 19 20 package com.puppycrawl.tools.checkstyle.checks.coding; 21 22 import com.puppycrawl.tools.checkstyle.StatelessCheck; 23 import com.puppycrawl.tools.checkstyle.api.AbstractCheck; 24 import com.puppycrawl.tools.checkstyle.api.DetailAST; 25 import com.puppycrawl.tools.checkstyle.api.TokenTypes; 26 import com.puppycrawl.tools.checkstyle.utils.CheckUtil; 27 import com.puppycrawl.tools.checkstyle.utils.TokenUtil; 28 29 /** 30 * <p> 31 * Checks that each variable declaration is in its own statement 32 * and on its own line. 33 * </p> 34 * <p> 35 * Rationale: <a 36 * href="https://checkstyle.org/styleguides/sun-code-conventions-19990420/CodeConventions.doc5.html#a2992"> 37 * the Java code conventions chapter 6.1</a> recommends that 38 * declarations should be one per line/statement. 39 * </p> 40 * <p> 41 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker} 42 * </p> 43 * <p> 44 * Violation Message Keys: 45 * </p> 46 * <ul> 47 * <li> 48 * {@code multiple.variable.declarations} 49 * </li> 50 * <li> 51 * {@code multiple.variable.declarations.comma} 52 * </li> 53 * </ul> 54 * 55 * @since 3.4 56 */ 57 @StatelessCheck 58 public class MultipleVariableDeclarationsCheck extends AbstractCheck { 59 60 /** 61 * A key is pointing to the warning message text in "messages.properties" 62 * file. 63 */ 64 public static final String MSG_MULTIPLE = "multiple.variable.declarations"; 65 66 /** 67 * A key is pointing to the warning message text in "messages.properties" 68 * file. 69 */ 70 public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma"; 71 72 @Override 73 public int[] getAcceptableTokens() { 74 return getRequiredTokens(); 75 } 76 77 @Override 78 public int[] getDefaultTokens() { 79 return getRequiredTokens(); 80 } 81 82 @Override 83 public int[] getRequiredTokens() { 84 return new int[] {TokenTypes.VARIABLE_DEF}; 85 } 86 87 @Override 88 public void visitToken(DetailAST ast) { 89 DetailAST nextNode = ast.getNextSibling(); 90 91 if (nextNode != null) { 92 final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA; 93 94 if (isCommaSeparated 95 || nextNode.getType() == TokenTypes.SEMI) { 96 nextNode = nextNode.getNextSibling(); 97 } 98 99 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 }