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://www.oracle.com/technetwork/java/javase/documentation/codeconventions-141270.html">
036 * the SUN Code conventions chapter 6.1</a> recommends that
037 * declarations should be one per line.
038 * </p>
039 * <p>
040 * An example of how to configure the check is:
041 * </p>
042 * <pre>
043 * &lt;module name="MultipleVariableDeclarations"/&gt;
044 * </pre>
045 */
046@StatelessCheck
047public class MultipleVariableDeclarationsCheck extends AbstractCheck {
048
049    /**
050     * A key is pointing to the warning message text in "messages.properties"
051     * file.
052     */
053    public static final String MSG_MULTIPLE = "multiple.variable.declarations";
054
055    /**
056     * A key is pointing to the warning message text in "messages.properties"
057     * file.
058     */
059    public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma";
060
061    @Override
062    public int[] getAcceptableTokens() {
063        return getRequiredTokens();
064    }
065
066    @Override
067    public int[] getDefaultTokens() {
068        return getRequiredTokens();
069    }
070
071    @Override
072    public int[] getRequiredTokens() {
073        return new int[] {TokenTypes.VARIABLE_DEF};
074    }
075
076    @Override
077    public void visitToken(DetailAST ast) {
078        DetailAST nextNode = ast.getNextSibling();
079
080        if (nextNode != null) {
081            final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA;
082
083            if (isCommaSeparated
084                || nextNode.getType() == TokenTypes.SEMI) {
085                nextNode = nextNode.getNextSibling();
086            }
087
088            if (nextNode != null
089                    && nextNode.getType() == TokenTypes.VARIABLE_DEF) {
090                final DetailAST firstNode = CheckUtil.getFirstNode(ast);
091                if (isCommaSeparated) {
092                    // Check if the multiple variable declarations are in a
093                    // for loop initializer. If they are, then no warning
094                    // should be displayed. Declaring multiple variables in
095                    // a for loop initializer is a good way to minimize
096                    // variable scope. Refer Feature Request Id - 2895985
097                    // for more details
098                    if (ast.getParent().getType() != TokenTypes.FOR_INIT) {
099                        log(firstNode, MSG_MULTIPLE_COMMA);
100                    }
101                }
102                else {
103                    final DetailAST lastNode = getLastNode(ast);
104                    final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode);
105
106                    if (firstNextNode.getLineNo() == lastNode.getLineNo()) {
107                        log(firstNode, MSG_MULTIPLE);
108                    }
109                }
110            }
111        }
112    }
113
114    /**
115     * Finds sub-node for given node maximum (line, column) pair.
116     * @param node the root of tree for search.
117     * @return sub-node with maximum (line, column) pair.
118     */
119    private static DetailAST getLastNode(final DetailAST node) {
120        DetailAST currentNode = node;
121        DetailAST child = node.getFirstChild();
122        while (child != null) {
123            final DetailAST newNode = getLastNode(child);
124            if (newNode.getLineNo() > currentNode.getLineNo()
125                || newNode.getLineNo() == currentNode.getLineNo()
126                    && newNode.getColumnNo() > currentNode.getColumnNo()) {
127                currentNode = newNode;
128            }
129            child = child.getNextSibling();
130        }
131
132        return currentNode;
133    }
134
135}