假設有一百張票由四個售票點同時在賣，請用多執行緒來程式設計此售票過程（請在程式設計中避免出現一張票號被列印多次以及出現0和負數票號的情況）。

程式碼如下：

package com.homework.lhh;

public class Ex02 {
    public static void main(String[] args) {
        Ticket ticket = new Ticket();
        GetTicket g1 = new GetTicket("售票點1", ticket);
        GetTicket g2 = new GetTicket("售票點2"
 
, ticket);
        GetTicket g3 = new GetTicket("售票點3", ticket);
        GetTicket g4 = new GetTicket("售票點4", ticket);

        g1.start();
        g2.start();
        g3.start();
        g4.start();
    }
}

class Ticket {
    private int ticketNum = 100;
    private int temp = 0;

    public int getTicketNum
 
() {
        return ticketNum;
    }

    public synchronized void getTicket() {
        if (ticketNum != 0) {
            ticketNum -= 1;
            temp++;
            try {
                Thread.sleep(100);
                System.out.println(Thread.currentThread().getName() + " 賣出了一張票，票號為 " + temp + "， 還剩 "
 
 + ticketNum + " 張票");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

class GetTicket extends Thread {

    private Ticket ticket;

    public GetTicket(String name, Ticket ticket) {
        super(name);
        this.ticket = ticket;
    }

    @Override
    public void run() {
        super.run();
        while (ticket.getTicketNum() != 0) {
            ticket.getTicket();
        }
    }
}