Implementation of a state machine, an example of a traffic light

TrafficLight.java

package com.github.zjor;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import static com.github.zjor.Sandbox.State.GREEN;
import static com.github.zjor.Sandbox.State.RED;
import static com.github.zjor.Sandbox.State.RED_YELLOW;
import static com.github.zjor.Sandbox.State.YELLOW;
import static com.github.zjor.Sandbox.Transition.of;

/**
 * 🔴🟡🟢⚪
 */
public class Sandbox {

    public enum State {
        RED,
        YELLOW,
        RED_YELLOW,
        GREEN
    }

    public record Transition(State next, long delay) {
        public static Transition of(State next, long delay) {
            return new Transition(next, delay);
        }
    }

    private Map<State, Transition> transitions = new HashMap<>();

    {
        transitions.put(RED, of(RED_YELLOW, 2000L));
        transitions.put(RED_YELLOW, of(GREEN, 500L));
        transitions.put(GREEN, of(YELLOW, 1500L));
        transitions.put(YELLOW, of(RED, 500L));
    }

    private State state = RED;
    private ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();

    public void render(State state) {
        switch (state) {
            case RED -> System.out.print("\r[ \uD83D\uDD34⚪⚪ ]==|");
            case RED_YELLOW -> System.out.print("\r[ \uD83D\uDD34\uD83D\uDFE1⚪ ]==|");
            case GREEN -> System.out.print("\r[ ⚪⚪\uD83D\uDFE2 ]==|");
            case YELLOW -> System.out.print("\r[ ⚪\uD83D\uDFE1⚪ ]==|");
        }
    }

    public void start() {
        executorService.schedule(() -> tick(), 0, TimeUnit.MILLISECONDS);
    }

    public void tick() {
        var t = transitions.get(state);
        render(state);
        state = t.next;
        executorService.schedule(() -> tick(), t.delay, TimeUnit.MILLISECONDS);
    }

    /*
    (state, condition) -> (action, state')

    red -> red_yellow -> green -> yellow

    (state, delay, state')
     */

    public static void main(String[] args) {
        (new Sandbox()).start();
    }

}