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;
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.utils.CommonUtil;
026
027/**
028 * <p>
029 * Checks whether file contains code. Files which are considered to have no code:
030 * </p>
031 * <ul>
032 * <li>
033 * File with no text
034 * </li>
035 * <li>
036 * File with single line comment(s)
037 * </li>
038 * <li>
039 * File with a multi line comment(s).
040 * </li>
041 * </ul>
042 * <p>
043 * To configure the check:
044 * </p>
045 * <pre>
046 * &lt;module name="NoCodeInFile"/&gt;
047 * </pre>
048 * <p>
049 * Example:
050 * </p>
051 * <p>
052 * Content of the files:
053 * </p>
054 * <pre>
055 * // single line comment // violation
056 * </pre>
057 * <pre>
058 * /* // violation
059 *  block comment
060 * *&#47;
061 * </pre>
062 * <p>
063 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
064 * </p>
065 * <p>
066 * Violation Message Keys:
067 * </p>
068 * <ul>
069 * <li>
070 * {@code nocode.in.file}
071 * </li>
072 * </ul>
073 *
074 * @since 8.33
075 */
076@StatelessCheck
077public class NoCodeInFileCheck extends AbstractCheck {
078
079    /**
080     * A key is pointing to the warning message text in "messages.properties"
081     * file.
082     */
083    public static final String MSG_KEY_NO_CODE = "nocode.in.file";
084
085    /** Line number used to log violation when no AST nodes are present in file. */
086    private static final int DEFAULT_LINE_NUMBER = 1;
087
088    @Override
089    public int[] getDefaultTokens() {
090        return getRequiredTokens();
091    }
092
093    @Override
094    public int[] getAcceptableTokens() {
095        return getRequiredTokens();
096    }
097
098    @Override
099    public int[] getRequiredTokens() {
100        return CommonUtil.EMPTY_INT_ARRAY;
101    }
102
103    @Override
104    public void finishTree(DetailAST ast) {
105        if (ast == null) {
106            log(DEFAULT_LINE_NUMBER, MSG_KEY_NO_CODE);
107        }
108    }
109}