001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2020 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 * To configure the check:
042 * </p>
043 * <pre>
044 * &lt;module name="MultipleVariableDeclarations"/&gt;
045 * </pre>
046 *
047 * @since 3.4
048 */
049@StatelessCheck
050public class MultipleVariableDeclarationsCheck extends AbstractCheck {
051
052    /**
053     * A key is pointing to the warning message text in "messages.properties"
054     * file.
055     */
056    public static final String MSG_MULTIPLE = "multiple.variable.declarations";
057
058    /**
059     * A key is pointing to the warning message text in "messages.properties"
060     * file.
061     */
062    public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma";
063
064    @Override
065    public int[] getAcceptableTokens() {
066        return getRequiredTokens();
067    }
068
069    @Override
070    public int[] getDefaultTokens() {
071        return getRequiredTokens();
072    }
073
074    @Override
075    public int[] getRequiredTokens() {
076        return new int[] {TokenTypes.VARIABLE_DEF};
077    }
078
079    @Override
080    public void visitToken(DetailAST ast) {
081        DetailAST nextNode = ast.getNextSibling();
082
083        if (nextNode != null) {
084            final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA;
085
086            if (isCommaSeparated
087                || nextNode.getType() == TokenTypes.SEMI) {
088                nextNode = nextNode.getNextSibling();
089            }
090
091            if (nextNode != null
092                    && nextNode.getType() == TokenTypes.VARIABLE_DEF) {
093                final DetailAST firstNode = CheckUtil.getFirstNode(ast);
094                if (isCommaSeparated) {
095                    // Check if the multiple variable declarations are in a
096                    // for loop initializer. If they are, then no warning
097                    // should be displayed. Declaring multiple variables in
098                    // a for loop initializer is a good way to minimize
099                    // variable scope. Refer Feature Request Id - 2895985
100                    // for more details
101                    if (ast.getParent().getType() != TokenTypes.FOR_INIT) {
102                        log(firstNode, MSG_MULTIPLE_COMMA);
103                    }
104                }
105                else {
106                    final DetailAST lastNode = getLastNode(ast);
107                    final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode);
108
109                    if (TokenUtil.areOnSameLine(firstNextNode, lastNode)) {
110                        log(firstNode, MSG_MULTIPLE);
111                    }
112                }
113            }
114        }
115    }
116
117    /**
118     * Finds sub-node for given node maximum (line, column) pair.
119     *
120     * @param node the root of tree for search.
121     * @return sub-node with maximum (line, column) pair.
122     */
123    private static DetailAST getLastNode(final DetailAST node) {
124        DetailAST currentNode = node;
125        final DetailAST child = node.getLastChild();
126        if (child != null) {
127            currentNode = getLastNode(child);
128        }
129
130        return currentNode;
131    }
132
133}