001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2026 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 * @since 3.4
043 */
044@StatelessCheck
045public class MultipleVariableDeclarationsCheck extends AbstractCheck {
046
047    /**
048     * A key is pointing to the warning message text in "messages.properties"
049     * file.
050     */
051    public static final String MSG_MULTIPLE = "multiple.variable.declarations";
052
053    /**
054     * A key is pointing to the warning message text in "messages.properties"
055     * file.
056     */
057    public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma";
058
059    /**
060     * Creates a new {@code MultipleVariableDeclarationsCheck} instance.
061     */
062    public MultipleVariableDeclarationsCheck() {
063        // no code by default
064    }
065
066    @Override
067    public int[] getAcceptableTokens() {
068        return getRequiredTokens();
069    }
070
071    @Override
072    public int[] getDefaultTokens() {
073        return getRequiredTokens();
074    }
075
076    @Override
077    public int[] getRequiredTokens() {
078        return new int[] {TokenTypes.VARIABLE_DEF};
079    }
080
081    @Override
082    public void visitToken(DetailAST ast) {
083        DetailAST nextNode = ast.getNextSibling();
084
085        if (nextNode != null) {
086            final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA;
087
088            if (isCommaSeparated
089                || nextNode.getType() == TokenTypes.SEMI) {
090                nextNode = nextNode.getNextSibling();
091            }
092
093            if (nextNode != null
094                    && nextNode.getType() == TokenTypes.VARIABLE_DEF) {
095                final DetailAST firstNode = CheckUtil.getFirstNode(ast);
096                if (isCommaSeparated) {
097                    // Check if the multiple variable declarations are in a
098                    // for loop initializer. If they are, then no warning
099                    // should be displayed. Declaring multiple variables in
100                    // a for loop initializer is a good way to minimize
101                    // variable scope. Refer Feature Request Id - 2895985
102                    // for more details
103                    if (ast.getParent().getType() != TokenTypes.FOR_INIT) {
104                        log(firstNode, MSG_MULTIPLE_COMMA);
105                    }
106                }
107                else {
108                    final DetailAST lastNode = getLastNode(ast);
109                    final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode);
110
111                    if (TokenUtil.areOnSameLine(firstNextNode, lastNode)) {
112                        log(firstNode, MSG_MULTIPLE);
113                    }
114                }
115            }
116        }
117    }
118
119    /**
120     * Finds sub-node for given node maximum (line, column) pair.
121     *
122     * @param node the root of tree for search.
123     * @return sub-node with maximum (line, column) pair.
124     */
125    private static DetailAST getLastNode(final DetailAST node) {
126        DetailAST currentNode = node;
127        final DetailAST child = node.getLastChild();
128        if (child != null) {
129            currentNode = getLastNode(child);
130        }
131
132        return currentNode;
133    }
134
135}