将参数传递给构造函数

Question

我从糟糕的代码中养成了糟糕的编码习惯，但是我正在努力解决这些问题。 我的主要问题是试图通过构造函数传递初始参数，我已经一年没有用 Java 编码了，所以让我知道所有错误！

public class AccountHolder {

     public static void main(String args[])
     {
        //Introduce scanner
           Scanner sc = new Scanner(System.in); //Used to take input from user
           System.out.println("Welcome to the bank program! Can you tell me your current balance?");

       input = sc.nextDouble();
       AccountHolder(input);
      }

        // Introduce private field members
        private static double annualInterestRate; //Constant to hold annual interest rate
        private static double fee; // Constant to hold the withdrawal fee
        private double balance; // variable to hold the balance
        private double rateUpdate; // variable to hold the value to update the rate
        private static double input; // variable to hold user input
        private double test; // variable to test whether or not user will drop below $100.

        // introduce a DecimalFormat object
        DecimalFormat twoPlace = new DecimalFormat("0.00"); // Used to keep values to 2 significant figures.

        // Introduce public methods

        public AccountHolder(double input) 
        {   
            balance = input;
        }

        public void deposit(double input)
        { 
            balance = balance + input;
            System.out.println("Your new balance is: $" + twoPlace.format(balance));
        }

        public void withdrawl(double input)
        {
            test = balance;
            balance = balance - input;

            if (balance < 100.0)
            {
                balance = balance + input;
                System.out.println("Your balance is not allowed to drop below $100.00. Please try again when you have more funds.");
            }

            if (test >= 500 && balance < 500)
            {
                balance = balance - fee;
                System.out.println("You have been charged an additional $50 for dropping below $500.00.");
            }

            System.out.println("Your new balance is: $" + twoPlace.format(balance));
        }



        public void monthlyInterest()
        {
            balance += balance * (annualInterestRate / 12.0);
        }

        public static void modifyMonthlyInterest(double rateUpdate)
        {
            annualInterestRate = rateUpdate;
            while (annualInterestRate <= 0 || annualInterestRate >= 1.0)
            {
                System.out.println("Error! Interest rates must be between 0 and 1. We need to keep our money!");
                annualInterestRate = sc.nextDouble();
            }

        }

        public String toString()
        {
            return String.format("$%.2f", balance);

        }



}

Answer 1

代替

AccountHolder(input);

你需要做

new AccountHolder(input);

当你缺少“new”时，它被解释为一个方法调用。 对于“new”，它被解释为对构造函数的调用。

PS：我想建议您查看变量的范围。 例如，您可以在“main”方法内定义“input”变量，而不是作为静态类变量。 这提高了代码的可读性。

Answer 2

这是你的构造函数：

public AccountHolder(double input) {   
        balance = input;
 }

并且您正在传递如下参数：

AccountHolder(input);

您缺少使用关键字new来实际创建该类的新实例...

喜欢

AccountHolder myHolder =  new  AccountHolder(input);