在如下Java代码片段中，`Bank`类定义了`deposit`和`withdraw`方法，其中`withdraw`方法可能会抛出自定义异常`BankException`。在`operate`方法中，如果先执行两次`deposit`操作，再执行两次`withdraw`操作，若初始账户余额为0，且两次`withdraw`操作分别尝试取款500和1000，则程序运行的结果会是什么？ ```java class BankException extends Exception { public BankException(String message) { super(message); } } class Bank { private double balance; public Bank(double initialBalance) { this.balance = initialBalance; } public double getBalance() { return balance; } public void setBalance(double balance) { this.balance = balance; } public void deposit(double amount) { this.setBalance(this.getBalance() + amount); System.out.println("存款金额："+amount+"，现有余额："+this.getBalance()); } public double withdraw(double amount) throws BankException { if (amount <= this.getBalance()) { this.setBalance(this.getBalance() - amount); System.out.println("取款金额：" + amount + "，现有余额：" + this.getBalance()); } else { BankException be = new BankException("余额不足，操作失败！"); throw be; } return this.getBalance(); } } public class Main { public static void main(String[] args) { try { operate(); } catch (BankException e) { System.err.println(e.getMessage()); } } public static void operate() throws BankException { Bank bank = new Bank(0); bank.deposit(300); bank.deposit(500); bank.withdraw(500); bank.withdraw(1000); System.out.println("任务完成！"); } } ```