java 模拟多人从同一个账户上取钱的过程 假设账户上有10000元钱，3人从上面随机取（范围为100至300）元钱，如果取完了，就提示已经没钱了。

可以使用Java中的线程和同步机制来模拟多人从同一个账户上取钱的过程。以下是示例代码：

public class BankAccount {
    private int balance = 10000;

    public synchronized void withdraw(int amount, String threadName) {
        if (balance >= amount) {
            System.out.println(threadName + " withdraws $" + amount + " from the account");
            balance -= amount;
            System.out.println("Current balance: $" + balance);
        } else {
            System.out.println(threadName + " tries to withdraw $" + amount + " from the account, but there is not enough money");
        }
    }
}

public class WithdrawThread implements Runnable {
    private BankAccount account;
    private String threadName;

    public WithdrawThread(BankAccount account, String threadName) {
        this.account = account;
        this.threadName = threadName;
    }

    @Override
    public void run() {
        while (true) {
            int amount = (int) (Math.random() * 201 + 100);
            account.withdraw(amount, threadName);
            try {
                Thread.sleep((int) (Math.random() * 1000));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        BankAccount account = new BankAccount();
        Thread t1 = new Thread(new WithdrawThread(account, "Thread 1"));
        Thread t2 = new Thread(new WithdrawThread(account, "Thread 2"));
        Thread t3 = new Thread(new WithdrawThread(account, "Thread 3"));
        t1.start();
        t2.start();
        t3.start();
    }
}

在上面的代码中，BankAccount类代表银行账户，它有一个balance成员变量表示账户余额，还有一个withdraw方法表示从账户上取钱。这个方法是同步方法，使用synchronized关键字来确保在多线程环境下只有一个线程可以执行该方法。

WithdrawThread类代表取钱的线程，它持有一个BankAccount对象和一个线程名字。它的run方法会不断地从账户上取钱，直到账户上没有钱为止。取钱的金额是随机的，范围为100至300。取完钱后，线程会休眠一段随机时间，模拟取钱的时间。

Main类创建了一个BankAccount对象和三个WithdrawThread对象，并将它们都启动。这样就可以模拟多人从同一个账户上取钱的过程了。当账户上没有钱时，取钱的线程会收到提示并停止取钱。