Java，在 do-while 循环结束时不注册用户输入

Question

我有这个代码:

import java.util.*;

public class MyAccount {
    public static double balance = 0.0;

    public static double deposit(double deposit){
        return balance += deposit;
    }
    //public void setBalance(double balance){
    //  this.balance = balance;
    //}
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String redo = "";
        do{
        System.out.println("What do you want to do today?");
        String answer= in.nextLine();
        if(answer.equals("deposit")){
            System.out.println("How much do you want to deposit?");
            double money = in.nextDouble();
            deposit(money);
        }
        System.out.println("Your balance is " + balance);
        System.out.println("Anything else(Y or N)?");
        redo = in.nextLine().toUpperCase();
        } while(redo.equals("Y"));
    }
}

该程序直到最后都运行良好。如果我将钱存入其中并到达“还有其他(Y 或 N)吗？”这一行。之后我无法输入任何内容；即使我有 redo串在那里。不过如果我不存钱，我可以输入redo的东西并且可以让程序循环。我该如何修复它，以便即使我存入一些东西它也会循环？

Answer 1

原因有点棘手。这是因为在调用in.nextDouble()之后，用户的\n仍然在输入流中，这样redo就会当您调用 redo = in.nextLine().toUpperCase() 时等于空字符串。要修复它，请添加 in.nextLine() ，如下所示:

    if(answer.equals("deposit")){
        System.out.println("How much do you want to deposit?");
        double money = in.nextDouble();
        in.nextLine();
        deposit(money);
    }

或者另一种选择是:

    if(answer.equals("deposit")){
        System.out.println("How much do you want to deposit?");
        double money = Double.parseDouble(in.nextLine());
        deposit(money);
    }