带条件/锁的Java线程同步

Question

嘿伙计们，所以我遇到了一些麻烦。所以任务是模拟咖啡店。这是一个有5个座位的咖啡厅。如果您在空座位时到达，您可以立即就座。但是如果你在所有5个座位都已满的时候到达，这意味着所有的顾客都在一起喝咖啡，你必须等待整个派对离开（所有5个座位都免费）才能坐下来。

必须使用Threads强制执行此操作。客户数量作为命令行参数传入。

我在将custs Thread数组传递给start / run方法时遇到了一些麻烦。我不确定条件是否正确执行等待线程。如果我将customerThread类中的计数器更改为id，那么每次id为5的线程显示它时就会锁定它。

import java.io.*;
import java.util.Scanner;
import java.util.concurrent.locks.*;


public class CoffeeShop {


public static void main(String[] args)
{


    Scanner infile = new Scanner(args[0]);
    //Queue<Thread[]> CoffeeWaitingQueue = new LinkedList<Thread[]>();
    //Queue<CustomerThread> CoffeeDrinkingQueue = new LinkedList<CustomerThread>();


    if (args.length != 1) {
        printUsage();
    }


    int num = 0;
    try
    {
        num = Integer.parseInt(args[0]);
    }
    catch (NumberFormatException e)
    {
        printUsage();
    }


    System.out.println("Coffee Shop");
    System.out .println("---------------------------------------------------"
            + "---------------------------------------------+--------"
            + "-------------------------------------------------------------------");

    //Thread emp = new EmployeeThread();
    //emp.start();

    Thread[] custs = new Thread[num];
    int counter = custs.length;


    for (int i = 1; i < num; i++)
    {
        custs[i] = new CustomerThread(i);
        custs[i].start();
    }

    for (int i = 1; i < num; i++)
    {
        try {
            custs[i].join();
        }
        catch (InterruptedException e) {
        }
    }

    System.exit(0);
}

private static void printUsage() {
    System.out.println("Usage: java SandwichShop <num>");
    System.out.println("  <num>: Number of customers.");
    System.exit(-1);
}

public static void randomSleep(int max) {
    try {
        Thread.sleep((int) (Math.random() * max));
    }
    catch (InterruptedException e) {
    }
}
}

class CustomerThread extends Thread {

private final Lock lock = new ReentrantLock();
private final Condition condition = lock.newCondition();
int counter = custs.length;

private int id;

public CustomerThread(int id)
{
    this.id = id;
}

public void run()
{

    drinkCoffee();
    leaveShop();


}

private void drinkCoffee()
{
    //int num = 0;
    //int num = 1;
    //num = customers;
    //int counter = custs.length;


    try{
        lock.lock();
        if(counter<5){
            System.out.println("Customer is in seat " +counter);
            ++counter;
        }else if(counter==5)
        {
            System.out.println("Customer is in seat " +counter);
            System.out.println("Shop is now full");
            while (counter>0) {
                condition.await();
            }
            ++counter;
            System.out.println(" in "+""+counter);
        }
    }
    catch (InterruptedException E1)
    {

    }
    finally {
        lock.unlock();
    }
}

private void leaveShop()
{
    try{
        lock.lock();
        System.out.println("Customer " + counter + " has left the seat");
        --counter;
        if(counter==0)
        {
            condition.signal();
        }
    }

    finally {
        lock.unlock();
    }
}

}