ANTLR4 grammar for a breakfast menu: https://craftinginterpreters.com/representing-code.html#rules-for-grammars

Breakfast.g4

grammar Breakfast;

breakfast  : ('toast' | 'biscuits' | 'English muffin' | protein) ('with' breakfast 'on the side')? ;
protein    : 'really'+ 'crispy bacon'
           | 'sausage'
           | ( 'scrambled' | 'poached' | 'fried' ) 'eggs' ;

WS : [ \t\r\n]+ -> skip ; // skip spaces, tabs, newlines

Main.java

package com.example.breakfast;

import com.example.breakfast.BreakfastParser.BreakfastContext;
import org.antlr.v4.runtime.CharStreams;
import org.antlr.v4.runtime.CommonTokenStream;

public class Main {
    public static void main(String[] args) {
        String source = "poached eggs with English muffin on the side";
        BreakfastLexer lexer = new BreakfastLexer(CharStreams.fromString(source));
        BreakfastParser parser = new BreakfastParser(new CommonTokenStream(lexer));
        BreakfastContext tree = parser.breakfast();
        TranslatingBreakfastVisitor visitor = new TranslatingBreakfastVisitor();

        System.out.println(visitor.visit(tree));
    }
}

TranslatingBreakfastVisitor.java

package com.example.breakfast;

import org.antlr.v4.runtime.tree.ErrorNode;
import org.antlr.v4.runtime.tree.ParseTree;
import org.antlr.v4.runtime.tree.RuleNode;
import org.antlr.v4.runtime.tree.TerminalNode;

public class TranslatingBreakfastVisitor implements BreakfastVisitor<String> {
    @Override
    public String visitBreakfast(BreakfastParser.BreakfastContext ctx) {
        StringBuilder sb = new StringBuilder();

        for (ParseTree child : ctx.children) {
            sb.append(child.accept(this));
        }

        return sb.toString();
    }

    @Override
    public String visitProtein(BreakfastParser.ProteinContext ctx) {
        StringBuilder sb = new StringBuilder();

        for (ParseTree child : ctx.children) {
            sb.append(child.accept(this));
        }

        return sb.toString();
    }

    @Override
    public String visitCrispiness(BreakfastParser.CrispinessContext ctx) {
        return "erg" + ", erg".repeat(Math.max(0, ctx.getChildCount() - 1));
    }

    @Override
    public String visitCooked(BreakfastParser.CookedContext ctx) {
        switch (ctx.getText()) {
            case "scrambled":
                return "roer";
            case "poached":
                return "gepocheerd ";
            case "fried":
                return "gefrituurd ";
            default:
                throw new IllegalStateException("Unexpected value: " + ctx.getText());
        }
    }

    @Override
    public String visitBread(BreakfastParser.BreadContext ctx) {
        switch (ctx.getText()) {
            case "toast":
                return "toast";
            case "biscuits":
                return "biscuit";
            case "English muffin":
                return "Engelse muffin";
            default:
                throw new IllegalStateException("Unexpected value: " + ctx.getText());
        }
    }

    @Override
    public String visit(ParseTree parseTree) {
        return parseTree.accept(this);
    }

    @Override
    public String visitChildren(RuleNode ruleNode) {
        return ruleNode.accept(this);
    }

    @Override
    public String visitTerminal(TerminalNode terminalNode) {
        switch (terminalNode.getText()) {
            case "with":
                return " met ";
            case "crispy bacon":
                return " knapperige bacon";
            case "eggs":
                return "ei";
            case "sausage":
                return "worst";
            case "on the side":
                return " erbij";
            default:
                throw new IllegalStateException("Unexpected value: " + terminalNode.getText());
        }
    }

    @Override
    public String visitErrorNode(ErrorNode errorNode) {
        return "(fout)";
    }
}

TranslatingBreakfastVisitor.kt

package com.example.breakfast

import com.example.breakfast.BreakfastParser.BreakfastContext
import com.example.breakfast.BreakfastParser.ProteinContext
import org.antlr.v4.runtime.ParserRuleContext
import org.antlr.v4.runtime.tree.ErrorNode
import org.antlr.v4.runtime.tree.ParseTree
import org.antlr.v4.runtime.tree.RuleNode
import org.antlr.v4.runtime.tree.TerminalNode

class TranslatingBreakfastVisitor : BreakfastVisitor<String> {
    override fun visit(tree: ParseTree): String {
        return tree.accept(this)
    }

    private fun visitChildren(ctx: ParserRuleContext): String {
        val sb = StringBuilder()

        ctx.children.forEach {
            sb.append(it.accept(this))
        }

        return sb.toString()
    }

    override fun visitBreakfast(ctx: BreakfastContext): String {
        return visitChildren(ctx)
    }

    override fun visitProtein(ctx: ProteinContext): String {
        return visitChildren(ctx)
    }

    override fun visitChildren(node: RuleNode): String {
        return node.accept(this)
    }

    override fun visitErrorNode(node: ErrorNode): String {
        return "(fout)"
    }

    override fun visitTerminal(node: TerminalNode): String {
        return when (val text = node.text) {
            "with" -> "met "
            "on the side" -> "erbij "
            "poached" -> "gepocheerde "
            "eggs" -> "eieren "
            "toast" -> "toast "
            "biscuit" -> "Amerikaans biscuit "
            "English muffin" -> "Engelse muffin "
            "really" -> "erg "
            "crispy bacon" -> "knapperige bacon "
            "sausage" -> "worst "
            "scrambled" -> "roer"
            "fried" -> "gefrituurde "
            else -> throw IllegalStateException("Unexpected value: $text")
        }
    }
}

Usage instructions

Prerequisites

• Java JDK
• Java JRE
• ANTLR 4.8 "complete" JAR

Compiling

java -jar antlr-4.8-complete.jar Breakfast.g4
javac -cp antlr-4.8-complete.jar Breakfast*.java

Parsing expressions with TestRig

% java --class-path ".:antlr-4.8-complete.jar" org.antlr.v4.gui.TestRig Breakfast breakfast -gui
poached eggs with English muffin on the side
^D

Using the generated parser and lexer from Java

mkdir -p com/example/breakfast
mv *.java com/example/breakfast
java -jar antlr-4.8-complete.jar -package com.example.breakfast -visitor -o com/example/breakfast Breakfast.g4
javac -cp antlr-4.8-complete.jar com/example/breakfast/*.java
java -cp ".:antlr-4.8-complete.jar" com.example.breakfast.Main