001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2019 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;
027
028/**
029 * <p>
030 * Checks that each variable declaration is in its own statement
031 * and on its own line.
032 * </p>
033 * <p>
034 * Rationale: <a
035 * href="https://checkstyle.org/styleguides/sun-code-conventions-19990420/CodeConventions.doc5.html#a2992">
036 * the Java code conventions chapter 6.1</a> recommends that
037 * declarations should be one per line/statement.
038 * </p>
039 * <p>
040 * To configure the check:
041 * </p>
042 * <pre>
043 * &lt;module name="MultipleVariableDeclarations"/&gt;
044 * </pre>
045 *
046 * @since 3.4
047 */
048@StatelessCheck
049public class MultipleVariableDeclarationsCheck extends AbstractCheck {
050
051    /**
052     * A key is pointing to the warning message text in "messages.properties"
053     * file.
054     */
055    public static final String MSG_MULTIPLE = "multiple.variable.declarations";
056
057    /**
058     * A key is pointing to the warning message text in "messages.properties"
059     * file.
060     */
061    public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma";
062
063    @Override
064    public int[] getAcceptableTokens() {
065        return getRequiredTokens();
066    }
067
068    @Override
069    public int[] getDefaultTokens() {
070        return getRequiredTokens();
071    }
072
073    @Override
074    public int[] getRequiredTokens() {
075        return new int[] {TokenTypes.VARIABLE_DEF};
076    }
077
078    @Override
079    public void visitToken(DetailAST ast) {
080        DetailAST nextNode = ast.getNextSibling();
081
082        if (nextNode != null) {
083            final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA;
084
085            if (isCommaSeparated
086                || nextNode.getType() == TokenTypes.SEMI) {
087                nextNode = nextNode.getNextSibling();
088            }
089
090            if (nextNode != null
091                    && nextNode.getType() == TokenTypes.VARIABLE_DEF) {
092                final DetailAST firstNode = CheckUtil.getFirstNode(ast);
093                if (isCommaSeparated) {
094                    // Check if the multiple variable declarations are in a
095                    // for loop initializer. If they are, then no warning
096                    // should be displayed. Declaring multiple variables in
097                    // a for loop initializer is a good way to minimize
098                    // variable scope. Refer Feature Request Id - 2895985
099                    // for more details
100                    if (ast.getParent().getType() != TokenTypes.FOR_INIT) {
101                        log(firstNode, MSG_MULTIPLE_COMMA);
102                    }
103                }
104                else {
105                    final DetailAST lastNode = getLastNode(ast);
106                    final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode);
107
108                    if (firstNextNode.getLineNo() == lastNode.getLineNo()) {
109                        log(firstNode, MSG_MULTIPLE);
110                    }
111                }
112            }
113        }
114    }
115
116    /**
117     * Finds sub-node for given node maximum (line, column) pair.
118     * @param node the root of tree for search.
119     * @return sub-node with maximum (line, column) pair.
120     */
121    private static DetailAST getLastNode(final DetailAST node) {
122        DetailAST currentNode = node;
123        final DetailAST child = node.getLastChild();
124        if (child != null) {
125            currentNode = getLastNode(child);
126        }
127
128        return currentNode;
129    }
130
131}