Java编写一个图形界面的火车票售票程序，有三个窗口用来显示售票及余票信息，两个按钮，分别为 开始售票 和 退出系统 点击开始售票按钮 三个窗口同时进行售票 票售完时 弹出消息框 提示已售完 点击 退出系统按钮 系统退出

好的，以下是一个简单的Java程序，实现了你要求的功能：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class TrainTicketSystem extends JFrame implements ActionListener {
    private JLabel lblTicket1, lblTicket2, lblTicket3;
    private JButton btnStart, btnExit;
    private int ticket1 = 100, ticket2 = 100, ticket3 = 100;

    public TrainTicketSystem() {
        setTitle("火车票售票程序");
        setSize(400, 150);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new GridLayout(2, 3));

        lblTicket1 = new JLabel("车次1余票：" + ticket1);
        add(lblTicket1);
        lblTicket2 = new JLabel("车次2余票：" + ticket2);
        add(lblTicket2);
        lblTicket3 = new JLabel("车次3余票：" + ticket3);
        add(lblTicket3);

        btnStart = new JButton("开始售票");
        btnStart.addActionListener(this);
        add(btnStart);

        add(new JLabel());
        add(new JLabel());

        btnExit = new JButton("退出系统");
        btnExit.addActionListener(this);
        add(btnExit);

        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == btnStart) {
            new Thread(new TicketSeller(1)).start();
            new Thread(new TicketSeller(2)).start();
            new Thread(new TicketSeller(3)).start();
        } else if (e.getSource() == btnExit) {
            System.exit(0);
        }
    }

    private class TicketSeller implements Runnable {
        private int trainNo;

        public TicketSeller(int trainNo) {
            this.trainNo = trainNo;
        }

        public void run() {
            while (true) {
                synchronized (this) {
                    if (trainNo == 1 && ticket1 > 0) {
                        ticket1--;
                        lblTicket1.setText("车次1余票：" + ticket1);
                    } else if (trainNo == 2 && ticket2 > 0) {
                        ticket2--;
                        lblTicket2.setText("车次2余票：" + ticket2);
                    } else if (trainNo == 3 && ticket3 > 0) {
                        ticket3--;
                        lblTicket3.setText("车次3余票：" + ticket3);
                    } else {
                        JOptionPane.showMessageDialog(null, "车次" + trainNo + "已售完");
                        break;
                    }
                }
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) {
        new TrainTicketSystem();
    }
}

这个程序采用了多线程的方式进行售票，每个车次对应一个线程。点击开始售票按钮时，会启动三个线程去售票，当某个车次票已售完时，会弹出消息框提示。点击退出系统按钮时，程序会退出。