001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 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 * <div>
029 * Checks whether file contains code.
030 * Java compiler is not raising errors on files with no code or all commented out.
031 * Files which are considered to have no code:
032 * </div>
033 *
034 * <ul>
035 * <li>
036 * File with no text
037 * </li>
038 * <li>
039 * File with single-line comment(s)
040 * </li>
041 * <li>
042 * File with a multi line comment(s).
043 * </li>
044 * </ul>
045 *
046 * @since 8.33
047 */
048@StatelessCheck
049public class NoCodeInFileCheck 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_KEY_NO_CODE = "nocode.in.file";
056
057    /** Line number used to log violation when no AST nodes are present in file. */
058    private static final int DEFAULT_LINE_NUMBER = 1;
059
060    @Override
061    public int[] getDefaultTokens() {
062        return getRequiredTokens();
063    }
064
065    @Override
066    public int[] getAcceptableTokens() {
067        return getRequiredTokens();
068    }
069
070    @Override
071    public int[] getRequiredTokens() {
072        return CommonUtil.EMPTY_INT_ARRAY;
073    }
074
075    @Override
076    public void finishTree(DetailAST ast) {
077        if (ast == null) {
078            log(DEFAULT_LINE_NUMBER, MSG_KEY_NO_CODE);
079        }
080    }
081}