ANTLR is a powerful parser generator for multiple programming languages including Java.

ANTLR contains 2 major modules:

• Runtime - For building and executing parsers/lexers generated in Java.
• Tool (The Parser Generator) - For generating parsers/lexers Java class.

ANTLR Tool Source Code files are provided in the distribution packge (antlr4-4.10.1.zip). You can download them at ANTLR Website.

You can also browse the source code below:

⏎ org/antlr/v4/tool/LabelElementPair.java

/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.tool;

import org.antlr.runtime.BitSet;
import org.antlr.v4.parse.ANTLRParser;
import org.antlr.v4.tool.ast.GrammarAST;

public class LabelElementPair {
    public static final BitSet tokenTypeForTokens = new BitSet();
    static {
        tokenTypeForTokens.add(ANTLRParser.TOKEN_REF);
        tokenTypeForTokens.add(ANTLRParser.STRING_LITERAL);
        tokenTypeForTokens.add(ANTLRParser.WILDCARD);
    }

    public GrammarAST label;
    public GrammarAST element;
    public LabelType type;

    public LabelElementPair(Grammar g, GrammarAST label, GrammarAST element, int labelOp) {
        this.label = label;
        this.element = element;
        // compute general case for label type
        if ( element.getFirstDescendantWithType(tokenTypeForTokens)!=null ) {
            if ( labelOp==ANTLRParser.ASSIGN ) type = LabelType.TOKEN_LABEL;
            else type = LabelType.TOKEN_LIST_LABEL;
        }
        else if ( element.getFirstDescendantWithType(ANTLRParser.RULE_REF)!=null ) {
            if ( labelOp==ANTLRParser.ASSIGN ) type = LabelType.RULE_LABEL;
            else type = LabelType.RULE_LIST_LABEL;
        }

        // now reset if lexer and string
        if ( g.isLexer() ) {
            if ( element.getFirstDescendantWithType(ANTLRParser.STRING_LITERAL)!=null ) {
                if ( labelOp==ANTLRParser.ASSIGN ) type = LabelType.LEXER_STRING_LABEL;
            }
        }
    }

    @Override
    public String toString() {
        return label.getText()+" "+type+" "+element.toString();
    }
}

⏎ org/antlr/v4/tool/LabelElementPair.java

Or download all of them as a single archive file:

File name: antlr-tool-4.10.1-sources.jar
File size: 347718 bytes
Release date: 2022-04-15
Download 

⇒ Donwload antlr4-4.10.1.zip

⇐ ANTLR Runtime Source Code

⇑ Download and Review ANTLR Parser Generator

⇑⇑ FAQ for ANTLR Parser Generator