小弟，最近学习java自定义异常，就是搞不明白怎么回事？希望那位高手给我编写个示例看看，最好是存款的示例，当存款为负数时候，给出异常，在此我先谢过了……

class balanceInsufficientException extends Exception {
    public balanceInsufficientException() {
        super("余额不足");
    }
}

class CashWithdraw {
     private double money = 100.0;
    public void withdraw(double value) throws balanceInsufficientException {
        if((money - value)<0) {
            throw new balanceInsufficientException();
        }
        money -= value;
    }

}

public class Test {
    public static void main(String... a) throws Exception {
        CashWithdraw cw = new CashWithdraw();
        cw. withdraw(50);
        cw. withdraw(60);
    }
}