Question

我是java的新手，我决定编写一个简单的程序来练习IF。这是它应该做的：

向用户询问货币。
询问用户他想转移的金额。
计算佣金率并向用户显示详细信息。
要求用户确认;如果他输入“y”，程序应该打印“A”。如果他输入“n”，程序应打印“B”。

以下是代码：

import java.util.Scanner;

public class CommissionRate {

static String Confirm;
static byte CommissionRate=10;
static String Commission="1%.";
static double TotalCost;
static double MoneyAmount;
static byte CurrencyNum;
static char CurrencySign;
static Scanner sc = new Scanner(System.in);
public static void Currency(){

    System.out.println("Please choose your desired currnecy.");
    System.out.println("1.USD");
    System.out.println("2.EUR");
    System.out.println("3.GBP");
    System.out.println("4.CAD");
    System.out.println("5.CNY");
    System.out.println("6.JPY");
    CurrencyNum = sc.nextByte();
    if (CurrencyNum==1|CurrencyNum==4) {

        CurrencySign= '$';
    }
    else {

        if (CurrencyNum==2){

            CurrencySign='€';
        }
        else {
            if (CurrencyNum==3){

                CurrencySign='£';
            }
            else {
                if (CurrencyNum==5|CurrencyNum==6){

                    CurrencySign='¥';
                }
            }
        }
    }
}
public static void MoneyAmount() {

    System.out.println("Please enter the amount of money you would like to transfer :");
    MoneyAmount = sc.nextDouble();
    if (MoneyAmount>499 & MoneyAmount<10000){
        CommissionRate=5;
        Commission="0.5%.";
    }
    else{
        if (MoneyAmount>10000){
            CommissionRate= 3;
            Commission="0.3%.";
        }
    }
    TotalCost = MoneyAmount + MoneyAmount * CommissionRate/1000;
    System.out.println("Please confirm the transfer. ( y/n ) ");
    System.out.println("A transfer of "+MoneyAmount+CurrencySign+".");
    System.out.println("Commission rate is "+Commission);
    System.out.println("You need to pay " + TotalCost+"." );
    sc.nextLine();
    Confirm = sc.nextLine();
    if (Confirm=="y"){
        System.out.println("A");
    }
    else if (Confirm=="n") {
        System.out.println("B");
    }
}
}

首先，程序不会等待用户确认/中止传输，它将打印“B”。然后，我读了this并添加了“sc.nextLine（）”。然而，该程序只是忽略了最后的if和不打印任何东西。关于导致问题的原因以及如何解决问题的任何想法？

p.s。：这是我在运行程序时得到的结果：

Please choose your desired currnecy.
1.USD
2.EUR
3.GBP
4.CAD
5.CNY
6.JPY
2   // my input
Please enter the amount of money you would like to transfer :
120  // my input
Please confirm the transfer. ( y/n ) 
A transfer of 120.0€.
Commission rate is 1%.
You need to pay 121.2.
y  // my input

Answer 1

请尝试

if (Confirm.equals("y")){

和

else if (Confirm.equals("n"))

使用==比较对象引用而不是值。

Answer 2

尝试equals代替==，一次应为sc.nextLine();

Confirm = sc.nextLine();
if (Confirm.equals("y")){

而不是

 sc.nextLine();
    Confirm = sc.nextLine();
    if (Confirm=="y"){

应用程序忽略Scanner.nextLine（）方法后的输入

2 个答案: