001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2017 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;
026
027/**
028 * <p>
029 * Checks if array initialization contains optional trailing comma.
030 * </p>
031 * <p>
032 * Rationale: Putting this comma in make is easier to change the
033 * order of the elements or add new elements on the end. Main benefit of a trailing
034 * comma is that when you add new entry to an array, no surrounding lines are changed.
035 * </p>
036 * <p>
037 * The check demands a comma at the end if neither left nor right curly braces
038 * are on the same line as the last element of the array.
039 * </p>
040 * <pre>
041 * return new int[] { 0 };
042 * return new int[] { 0
043 *     };
044 * return new int[] {
045 *     0 };
046 * </pre>
047 * <pre>
048 * {
049 *     100000000000000000000,
050 *     200000000000000000000, // OK
051 * }
052 *
053 * {
054 *     100000000000000000000,
055 *     200000000000000000000,
056 *     300000000000000000000,  // Just this line added, no other changes
057 * }
058 * </pre>
059 * <p>
060 * If closing brace is on the same line as training comma, this benefit is gone
061 * (as the Check does not demand a certain location of curly braces the following
062 * two cases will not produce a violation):
063 * </p>
064 * <pre>
065 * {100000000000000000000,
066 *     200000000000000000000,} // Trailing comma not needed, line needs to be modified anyway
067 *
068 * {100000000000000000000,
069 *     200000000000000000000, // Modified line
070 *     300000000000000000000,} // Added line
071 * </pre>
072 * <p>
073 * If opening brace is on the same line as training comma there's also (more arguable) problem:
074 * </p>
075 * <pre>
076 * {100000000000000000000, // Line cannot be just duplicated to slightly modify entry
077 * }
078 *
079 * {100000000000000000000,
080 *     100000000000000000001, // More work needed to duplicate
081 * }
082 * </pre>
083 * <p>
084 * An example of how to configure the check is:
085 * </p>
086 * <pre>
087 * &lt;module name="ArrayTrailingComma"/&gt;
088 * </pre>
089 * @author o_sukhodolsky
090 */
091@StatelessCheck
092public class ArrayTrailingCommaCheck extends AbstractCheck {
093
094    /**
095     * A key is pointing to the warning message text in "messages.properties"
096     * file.
097     */
098    public static final String MSG_KEY = "array.trailing.comma";
099
100    @Override
101    public int[] getDefaultTokens() {
102        return getRequiredTokens();
103    }
104
105    @Override
106    public int[] getAcceptableTokens() {
107        return getRequiredTokens();
108    }
109
110    @Override
111    public int[] getRequiredTokens() {
112        return new int[] {TokenTypes.ARRAY_INIT};
113    }
114
115    @Override
116    public void visitToken(DetailAST arrayInit) {
117        final DetailAST rcurly = arrayInit.findFirstToken(TokenTypes.RCURLY);
118        final DetailAST previousSibling = rcurly.getPreviousSibling();
119
120        if (arrayInit.getLineNo() != rcurly.getLineNo()
121                && arrayInit.getChildCount() != 1
122                && rcurly.getLineNo() != previousSibling.getLineNo()
123                && arrayInit.getLineNo() != previousSibling.getLineNo()
124                && previousSibling.getType() != TokenTypes.COMMA) {
125            log(rcurly.getLineNo(), MSG_KEY);
126        }
127    }
128}