001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2026 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 all numerical literal prefixes, infixes, and suffixes are written
030 * using lowercase letters (for example prefixes : {@code 0x, 0b},
031 * infixes : {@code e, p}, suffixes : {@code f, d}).
032 * This convention follows the
033 * <a href="https://cr.openjdk.org/~alundblad/styleguide/index-v6.html#toc-literals">
034 * OpenJDK Style Guide</a>.
035 * </div>
036 *
037 * <p><b>ATTENTION:</b></p>
038 *
039 * <p>This check ignores the {@code L} suffix for long literals,
040 * as using an uppercase {@code L} is a widely accepted and recommended
041 * practice to avoid confusion with the digit {@code 1}.</p>
042 *
043 * @since 13.2.0
044 */
045@StatelessCheck
046public class NumericalPrefixesInfixesSuffixesCharacterCaseCheck extends AbstractCheck {
047
048    /**
049     * A key is pointing to the warning message text in "messages.properties" file.
050     */
051    public static final String MSG_PREFIX = "numerical.literal.prefix";
052
053    /**
054     * A key is pointing to the warning message text in "messages.properties" file.
055     */
056    public static final String MSG_INFIX = "numerical.literal.infix";
057
058    /**
059     * A key is pointing to the warning message text in "messages.properties" file.
060     */
061    public static final String MSG_SUFFIX = "numerical.literal.suffix";
062
063    /**
064     * Creates a new {@code NumericalPrefixesInfixesSuffixesCharacterCaseCheck} instance.
065     */
066    public NumericalPrefixesInfixesSuffixesCharacterCaseCheck() {
067        // no code by default
068    }
069
070    @Override
071    public int[] getDefaultTokens() {
072        return getRequiredTokens();
073    }
074
075    @Override
076    public int[] getAcceptableTokens() {
077        return getRequiredTokens();
078    }
079
080    @Override
081    public int[] getRequiredTokens() {
082        return new int[] {TokenTypes.NUM_LONG, TokenTypes.NUM_INT,
083            TokenTypes.NUM_FLOAT, TokenTypes.NUM_DOUBLE,
084        };
085    }
086
087    @Override
088    public void visitToken(DetailAST ast) {
089        final String text = ast.getText();
090        final boolean isHex = text.startsWith("0x");
091        if (text.startsWith("0X") || text.startsWith("0B")) {
092            log(ast, MSG_PREFIX);
093        }
094        else if (!isHex && text.contains("E") || text.contains("P")) {
095            log(ast, MSG_INFIX);
096        }
097        else if ((text.endsWith("F") || text.endsWith("D")) && (!isHex || text.contains("p"))) {
098            log(ast, MSG_SUFFIX);
099        }
100    }
101
102}