001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2024 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.api.TokenTypes;
026
027/**
028 * <div>
029 * Checks that long constants are defined with an upper ell. That is {@code 'L'}
030 * and not {@code 'l'}. This is in accordance with the Java Language Specification,
031 * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-3.html#jls-3.10.1">
032 * Section 3.10.1</a>.
033 * </div>
034 *
035 * <p>
036 * Rationale: The lower-case ell {@code 'l'} looks a lot like {@code 1}.
037 * </p>
038 *
039 * <p>
040 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
041 * </p>
042 *
043 * <p>
044 * Violation Message Keys:
045 * </p>
046 * <ul>
047 * <li>
048 * {@code upperEll}
049 * </li>
050 * </ul>
051 *
052 * @since 3.0
053 */
054@StatelessCheck
055public class UpperEllCheck extends AbstractCheck {
056
057    /**
058     * A key is pointing to the warning message text in "messages.properties"
059     * file.
060     */
061    public static final String MSG_KEY = "upperEll";
062
063    @Override
064    public int[] getDefaultTokens() {
065        return getRequiredTokens();
066    }
067
068    @Override
069    public int[] getAcceptableTokens() {
070        return getRequiredTokens();
071    }
072
073    @Override
074    public int[] getRequiredTokens() {
075        return new int[] {TokenTypes.NUM_LONG};
076    }
077
078    @Override
079    public void visitToken(DetailAST ast) {
080        if (ast.getText().endsWith("l")) {
081            log(ast, MSG_KEY);
082        }
083    }
084
085}