红绿灯路口

/*
 * Leetcode Problem 1279: Traffic Light Controlled Intersection
 *
 * Problem Statement:
 * There is an intersection with a traffic light. The traffic light can be in one of three states: green, yellow, or red. Given a series of cars arriving at the intersection,
 * each with an arrival time and direction, implement a system that controls the traffic light to avoid collisions and ensure cars proceed safely.
 *
 * Approach using Java Streams:
 * 1. Use a blocking queue to manage car arrivals and traffic light state changes.
 * 2. Process car entries in a stream to simulate concurrent processing.
 */

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.stream.IntStream;

class TrafficLightStream {
    private final AtomicBoolean isNorthSouthGreen = new AtomicBoolean(true);
    private final BlockingQueue<Car> queue = new LinkedBlockingQueue<>();

    // Car class
    static class Car {
        private final int carId;
        private final int direction;

        public Car(int carId, int direction) {
            this.carId = carId;
            this.direction = direction;
        }

        public int getDirection() {
            return direction;
        }
    }

    public void processCars() {
        queue.forEach(car -> {
            synchronized (this) {
                while ((isNorthSouthGreen.get() && (car.getDirection() == 2 || car.getDirection() == 3)) ||
                       (!isNorthSouthGreen.get() && (car.getDirection() == 0 || car.getDirection() == 1))) {
                    try {
                        wait();
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                    }
                }
                System.out.println("Car " + car.carId + " from direction " + car.getDirection() + " is passing.");
                isNorthSouthGreen.set(!isNorthSouthGreen.get());
                notifyAll();
            }
        });
    }

    public void addCar(Car car) {
        queue.add(car);
    }
}

public class MainStream {
    public static void main(String[] args) {
        TrafficLightStream trafficLight = new TrafficLightStream();
        IntStream.range(1, 3).forEach(i -> trafficLight.addCar(new TrafficLightStream.Car(i, i % 4)));
        trafficLight.processCars();
    }
}