001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2022 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 * <p>
047 * Example:
048 * </p>
049 * <pre>
050 * public class Test {
051 *   public void myTest() {
052 *     int mid;
053 *     int high;
054 *     // ...
055 *
056 *     int lower, higher; // violation
057 *     // ...
058 *
059 *     int value,
060 *         index; // violation
061 *     // ...
062 *
063 *     int place = mid, number = high;  // violation
064 *   }
065 * }
066 * </pre>
067 * <p>
068 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
069 * </p>
070 * <p>
071 * Violation Message Keys:
072 * </p>
073 * <ul>
074 * <li>
075 * {@code multiple.variable.declarations}
076 * </li>
077 * <li>
078 * {@code multiple.variable.declarations.comma}
079 * </li>
080 * </ul>
081 *
082 * @since 3.4
083 */
084@StatelessCheck
085public class MultipleVariableDeclarationsCheck extends AbstractCheck {
086
087    /**
088     * A key is pointing to the warning message text in "messages.properties"
089     * file.
090     */
091    public static final String MSG_MULTIPLE = "multiple.variable.declarations";
092
093    /**
094     * A key is pointing to the warning message text in "messages.properties"
095     * file.
096     */
097    public static final String MSG_MULTIPLE_COMMA = "multiple.variable.declarations.comma";
098
099    @Override
100    public int[] getAcceptableTokens() {
101        return getRequiredTokens();
102    }
103
104    @Override
105    public int[] getDefaultTokens() {
106        return getRequiredTokens();
107    }
108
109    @Override
110    public int[] getRequiredTokens() {
111        return new int[] {TokenTypes.VARIABLE_DEF};
112    }
113
114    @Override
115    public void visitToken(DetailAST ast) {
116        DetailAST nextNode = ast.getNextSibling();
117
118        if (nextNode != null) {
119            final boolean isCommaSeparated = nextNode.getType() == TokenTypes.COMMA;
120
121            if (isCommaSeparated
122                || nextNode.getType() == TokenTypes.SEMI) {
123                nextNode = nextNode.getNextSibling();
124            }
125
126            if (nextNode != null
127                    && nextNode.getType() == TokenTypes.VARIABLE_DEF) {
128                final DetailAST firstNode = CheckUtil.getFirstNode(ast);
129                if (isCommaSeparated) {
130                    // Check if the multiple variable declarations are in a
131                    // for loop initializer. If they are, then no warning
132                    // should be displayed. Declaring multiple variables in
133                    // a for loop initializer is a good way to minimize
134                    // variable scope. Refer Feature Request Id - 2895985
135                    // for more details
136                    if (ast.getParent().getType() != TokenTypes.FOR_INIT) {
137                        log(firstNode, MSG_MULTIPLE_COMMA);
138                    }
139                }
140                else {
141                    final DetailAST lastNode = getLastNode(ast);
142                    final DetailAST firstNextNode = CheckUtil.getFirstNode(nextNode);
143
144                    if (TokenUtil.areOnSameLine(firstNextNode, lastNode)) {
145                        log(firstNode, MSG_MULTIPLE);
146                    }
147                }
148            }
149        }
150    }
151
152    /**
153     * Finds sub-node for given node maximum (line, column) pair.
154     *
155     * @param node the root of tree for search.
156     * @return sub-node with maximum (line, column) pair.
157     */
158    private static DetailAST getLastNode(final DetailAST node) {
159        DetailAST currentNode = node;
160        final DetailAST child = node.getLastChild();
161        if (child != null) {
162            currentNode = getLastNode(child);
163        }
164
165        return currentNode;
166    }
167
168}