设计一个java程序，能够让多个用户同时从4个销售点完成100张票的购票操作。

这个问题涉及到多线程编程和同步问题，可以采用Java的并发包来实现。以下是一个基本的程序框架：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class TicketSellingSystem {
    public static void main(String[] args) {
        // 创建销售点
        TicketBox[] ticketBoxes = new TicketBox[4];
        for (int i = 0; i < 4; i++) {
            ticketBoxes[i] = new TicketBox(i + 1, 100);
        }

        // 创建线程池
        ExecutorService executorService = Executors.newFixedThreadPool(10);

        // 创建用户购票任务
        for (int i = 1; i <= 10; i++) {
            executorService.execute(new User(i, ticketBoxes));
        }

        // 关闭线程池
        executorService.shutdown();
    }
}

class User implements Runnable {
    private int id;
    private TicketBox[] ticketBoxes;

    public User(int id, TicketBox[] ticketBoxes) {
        this.id = id;
        this.ticketBoxes = ticketBoxes;
    }

    @Override
    public void run() {
        // 随机选择一个销售点购票
        int index = (int) (Math.random() * ticketBoxes.length);
        TicketBox ticketBox = ticketBoxes[index];

        // 购买1张票
        if (ticketBox.sell(1)) {
            System.out.println("User " + id + " bought 1 ticket from TicketBox " + ticketBox.getId());
        } else {
            System.out.println("User " + id + " failed to buy ticket from TicketBox " + ticketBox.getId());
        }
    }
}

class TicketBox {
    private int id;
    private int total;
    private int sold;

    public TicketBox(int id, int total) {
        this.id = id;
        this.total = total;
        this.sold = 0;
    }

    public synchronized boolean sell(int count) {
        if (sold + count > total) {
            return false;
        }
        sold += count;
        return true;
    }

    public int getId() {
        return id;
    }
}

程序中创建了4个销售点（`TicketBox`对象），每个销售点都有100张票。创建了10个用户（`User`对象），每个用户随机选择一个销售点进行购票操作。购票操作使用`synchronized`关键字进行同步，确保多个用户不会同时购买同一张票。最后，使用线程池来管理并发任务，确保多个用户同时购票。