java编写一个基于图形用户界面的火车票购票模拟系统。该系统主界面包括三个售票窗口区域，以及两个按钮： “开始售票” 和“退出系统”。点击“开始售票”按钮，三个窗口同时开始售票（启动三个线程同时售票），三个售票窗口动态的显示正在售票及剩余票量信息。若票全部售完（总票量在代码中自行指定），将弹出消息框，提示“车票已售完”，点击“退出系统”按钮时，系统退出。

好的，以下是一个示例Java代码，使用Java Swing库来实现该系统：

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.concurrent.atomic.AtomicInteger;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class TicketSystem {
    private JFrame frame;
    private JLabel label1;
    private JLabel label2;
    private JLabel label3;
    private JButton startButton;
    private JButton quitButton;
    private AtomicInteger ticketsSold;
    private int totalTickets;
    private boolean isSelling;

    public TicketSystem(int totalTickets) {
        this.totalTickets = totalTickets;
        this.ticketsSold = new AtomicInteger(0);
        this.isSelling = false;
        createUI();
    }

    private void createUI() {
        frame = new JFrame("火车票购票模拟系统");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        label1 = new JLabel("售票窗口1: 0/" + totalTickets);
        panel.add(label1);
        label2 = new JLabel("售票窗口2: 0/" + totalTickets);
        panel.add(label2);
        label3 = new JLabel("售票窗口3: 0/" + totalTickets);
        panel.add(label3);
        startButton = new JButton("开始售票");
        startButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                startSelling();
            }
        });
        panel.add(startButton);
        quitButton = new JButton("退出系统");
        quitButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                quit();
            }
        });
        panel.add(quitButton);
        frame.getContentPane().add(panel, BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }

    private void startSelling() {
        if (!isSelling) {
            isSelling = true;
            Thread t1 = new Thread(new TicketSeller(1));
            Thread t2 = new Thread(new TicketSeller(2));
            Thread t3 = new Thread(new TicketSeller(3));
            t1.start();
            t2.start();
            t3.start();
        }
    }

    private void updateUI(int window) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                if (window == 1) {
                    label1.setText("售票窗口1: " + ticketsSold + "/" + totalTickets);
                } else if (window == 2) {
                    label2.setText("售票窗口2: " + ticketsSold + "/" + totalTickets);
                } else {
                    label3.setText("售票窗口3: " + ticketsSold + "/" + totalTickets);
                }
            }
        });
    }

    private void quit() {
        int result = JOptionPane.showConfirmDialog(frame, "确定退出系统吗？", "退出", JOptionPane.YES_NO_OPTION);
        if (result == JOptionPane.YES_OPTION) {
            System.exit(0);
        }
    }

    private class TicketSeller implements Runnable {
        private int window;

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

        @Override
        public void run() {
            while (ticketsSold.get() < totalTickets) {
                // 模拟售票过程
                // ...
                // 更新票数
                ticketsSold.incrementAndGet();
                // 更新界面
                updateUI(window);
            }
            JOptionPane.showMessageDialog(frame, "车票已售完");
            isSelling = false;
        }
    }

    public static void main(String[] args) {
        TicketSystem system = new TicketSystem(100);
    }
}

上述代码中的 `TicketSeller` 类实现了售票线程，通过 `AtomicInteger` 类来实现线程安全的票数计数。在售票过程中，通过 `SwingUtilities.invokeLater` 方法来更新界面。在点击“退出系统”按钮时，弹出确认对话框，确认后退出程序。