有人可以解释为什么我的打印方法不起作用吗？

Question

我试图调用getName，并getBalance从另一个名为类的方法Account在银行类我printbalances方法。但它不起作用，它在输入客户和余额后打印为空。有人可以解释为什么以及如何解决它吗？老实说，我不知道为什么它不起作用。

这是调用它的类：

class Bank {

    ArrayList<Account> accounts = new ArrayList<>();

    Scanner input = new Scanner(System.in);

    Scanner q;

    String name;

    double balance;

    private Account account = new Account(name, balance);

    public void enterCustomers() {

        System.out.println("Enter customer names or press q to quit entering names: ");

        while (true) {

            String name;

            double balance;

            System.out.print("Enter a customer name: ");

            name = input.next();

            if ("q".equals(name)) { //tried using == to break but wouldnt work so tried .equals since comparing strings and works

                break;

            }

    }

这是存储 get 方法的类：

class Account {

    private String name;

    private double balance;

    public Account(String name, double balance) {

        this.name = name;

        this.balance = balance;

    }

    public String getName() {

        return name;

    }

    //public void setName(String name) {

    //  this.name = name;

    //}

    public double getBalance() {

        return balance;

    }

    //public void setBalance(double balance) {

    //  this.balance = balance;

    //}

    public void deposit(double amount) {

        balance += amount;

    }

    public void withdrawal(double amount) {

        if (balance >= amount) {

            balance -= amount;

        } else {

            System.out.println(" Insufficient Balance. ");

        }

    }

}

它给我的输出是这样的：

Enter customer names or press q to quit entering names: 

Enter a customer name: john

Enter the opening balance : 200

Enter a customer name: mike

Enter the opening balance : 2

Enter a customer name: q

==========================

Opening account balance

==========================

Customer            Balance

==========================

null0.0

(1)deposit (2)withdraw (0)quit

我不知道为什么会null 0.0出现，有人可以解释为什么吗？

Answer 1

有没有更多的参考account？您可能会在某个时候覆盖它，因为它的名称null为0.0

Answer 2

现在你正在account像这样初始化：private Account account = new Account(name, balance);但是这里name和balance没有初始化，所以null默认情况下它们分别是和 零。看起来更像是您想打印特定Account对象的名称和余额，因此我会将其作为参数传递给printBalances：public void printBalances(Account account) {&nbsp; &nbsp; System.out.println("==========================");&nbsp; &nbsp; System.out.println("Customer&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Balance");&nbsp; &nbsp; System.out.println("==========================");&nbsp; &nbsp; System.out.println(account.getName() + " : " + account.getBalance());}或者，如果您想打印accounts ArrayList:public void printBalances() {&nbsp; &nbsp; System.out.println("==========================");&nbsp; &nbsp; System.out.println("Customer&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Balance");&nbsp; &nbsp; System.out.println("==========================");&nbsp; &nbsp; for(Account account : accounts) {&nbsp; &nbsp; &nbsp; &nbsp; System.out.println(account.getName() + " : " + account.getBalance());&nbsp; &nbsp; }}