java - 如何设置 overdraw 限额

Question

我想做的是设置 overdraw 限额，即 -150 如果余额为 -150，用户将无法再提款。我的代码如下:

提现方式

public void Withdraw(double amount){


    if (amount + 5 > balance ){ //If amount and transaction fee is greater than balance then apply for overdraft
        System.out.println("Insufficent funds");
        System.out.println("Would you like to apply for an ovedraft?");
        System.out.println("1:Yes");
        System.out.println("2:No, return me back to menus");
        Choice = Option.nextLine();
        if (Choice.equalsIgnoreCase("1")){
         if((balance = balance - amount+5)<=-150){   //If balance is grater than 150 , apply for overdraft
             System.out.println("You have exceeded your Overdraft Limit, you will now be returned back to the menus");
         return;

        }
        else{ //if not exceeding bank balance
            balance -= amount + 5; 
            System.out.println("You have withdrawen £" + amount);
            System.err.println("You now have a balance of £" +balance);
            return; 
        }
    }
}

}

它们都在同一个类中，即“帐户”，现在发生的是消息确实发生了-(“您已经超过了 overdraw 限额，您现在将返回到菜单”)并返回到菜单但是当我去检查余额时，钱仍然被扣除并显示超过-150的余额，例如。 -190 我怎样才能使 -150 是限制而不是扣除更多。希望这个问题得到理解。

Answer 1

问题是:

if ((balance = balance - amount + 5) <= -150) {

这里的关键是 = .即在支票之前分配新金额。

这样的事情可能会避免这个问题。

    if (balance - amount - 5 < 0) {
        System.out.println("Insufficent funds");
        System.out.println("Would you like to apply for an ovedraft?");
        System.out.println("1:Yes");
        System.out.println("2:No, return me back to menus");
        Choice = Option.nextLine();
        if (Choice.equalsIgnoreCase("1")) {
            if (balance - amount - 5 <= -150) {
                System.out.println("You have exceeded your Overdraft Limit, you will now be returned back to the menus");
            } else { //if not exceeding bank balance
                balance -= amount + 5;
                System.out.println("You have withdrawen £" + amount);
                System.err.println("You now have a balance of £" + balance);
            }

请注意更明确的计算 ( if (balance - amount - 5 <= -150) )，它使用 <= 0 模拟数学和比较.这通常更容易理解。