Question

我无法弄清楚如何让我的main方法中的double balance1等于我的menu方法中的double acctBal。我将0分配给了acctBal，因为我不确定如何将它等同于任何balance1。我在我说的那条线旁边放了一些星号。

公共班级ATM {

public static Scanner kbd;

public static void main(String[] args) {
    String acctNum, acctPword;
    String balance;
    int x = 1;
    kbd = new Scanner(System.in);

    System.out.print("Enter your account number: ");
    acctNum = kbd.nextLine();

    System.out.print("Enter your account password: ");
    acctPword = kbd.nextLine();
    balance = checkID(acctNum, acctPword);
    double balance1 = Double.parseDouble(balance);
    System.out.println("You currently have $" + String.format("%.2f",balance1));*********************************

    while (balance.equals("error") && x <4){
        System.out.println("Wrong password try again.");
        System.out.print("Enter your account password: ");
        acctPword = kbd.nextLine();
        x++;
    }

    if (x == 4)
        System.out.println("Maximum number of attempts reached, Please try again later.");

    if (x == 1){
        menu();
    }

    kbd.close();
}

/**
 * Determines if acctNum is a valid account number, and pwd is the correct
 * password for the account.
 * @param acctNum The account number to be checked
 * @param pwd The password to be checked
 * @return If the account information is valid, returns the current account
 * balance, as a string. If the account information is invalid, returns
 * the string "error".
 */
public static String checkID(String acctNum, String pwd)
{
    String result = "error";

    // Strings a, b, and c contain the valid account numbers and passwords.
    // For each string, the account number is listed first, followed by
    // a space, followed by the password for the account, followed by a space,
    // followed by the current balance.
    String a = "44567-5 mypassword 520.36";
    String b = "1234567-6 anotherpassword 48.20";
    String c = "4321-0 betterpassword 96.74";

    if (acctNum.equals("44567-5") && pwd.equals("mypassword")){
        result = "520.36";
        return result;
    }

    if (acctNum.equals("1234567-6") && pwd.equals("anotherpassword")){
        result = "48.20";
        return result;
    }

    if (acctNum.equals("4321-0") && pwd.equals("betterpassword")){
        result = "96.74";
        return result;
    }

    return result;
}

public static void menu(){
    int x = 0;
    double acctBal = 0.0, deposit = 0.0, withAmnt = 0.0;**********this acctBal needs to equal balance1.

    System.out.println("1. Display Balance \n2. Deposit\n3. Withdraw\n4. Log Out");
    x = kbd.nextInt();
    switch(x){
    case 1:
        displayBalance(acctBal);
        break;
    case 2: 
        deposit(acctBal, deposit);
        break;
    case 3:
        withdraw(acctBal, withAmnt);
        break;
    case 4: 
        System.out.println("Have a nice day.");
        break;
    }


}

public static double deposit(double acctBal, double depAmnt){

    System.out.print("How much money would you like to deposit? $");
    depAmnt = kbd.nextDouble();
    acctBal = acctBal + depAmnt;
    System.out.println("Your balance is now at $" + String.format("%.2f", acctBal));
    return acctBal;
}

public static double withdraw(double acctBal, double withAmnt){

    System.out.print("How much money would you like to withdraw? $");
    withAmnt = kbd.nextDouble();

    if (acctBal <= 0){
        System.out.println("You do not have any money.");
        return acctBal;
    }

    if (acctBal < withAmnt){
        System.out.print("You do not have enough money.\nHow much money would you like to withdraw? $");
        withAmnt = kbd.nextDouble();
    }
    else{
        acctBal = acctBal - withAmnt;
    }

    return acctBal;
}

public static double displayBalance(double balance){
    System.out.println("Your balance is $" + String.format("%.2f", balance));
    return balance;
}

Answer 1

您可以更改menu()方法以接受参数（称为balance）并在调用main方法时传递menu()的值，例如：

public static void menu(double acctBal){
    double deposit = 0.0; //Other variables
}

并使用main从balance拨打电话，例如：

if (x == 1){
    menu(balance);
}

Answer 2

您的代码有问题，您不会处理checkID返回＆＃34;错误＆＃34;的情况。你不能分配＆＃34;错误＆＃34;到一些String，然后尝试从该String转换一个double。

次要修复

balance = checkID(acctNum, acctPword);
double balance1 = 0.0;

if (balance.equals("error"))
{
    // TODO: do something with invalid number.
}
else
{
    balance1 = Double.parseDouble(balance);
}
System.out.println("You currently have $" + String.format("%.2f",balance1));

从主程序获取数据

2 个答案: