使用从一个类到另一个类的方法

Question

我在使用最后一种方法时遇到麻烦。我被告知，我必须在我的bank类的monthFee方法中使用BankAccount.class中的adjust方法，但无法弄清楚。我尝试了多种不同的方法，但无法正常工作。我们需要用月费调整帐户余额。

  

Bank.java:33：错误：BankAccount类中的方法Adjust不能为   适用于给定的类型； BankAccount.adjust（）; ^
  必需：两次发现：无参数原因：实际和正式   参数列表的长度1错误不同

     

Bank.java:33：错误：不能取消引用double Fee.adjust（）; 1个   错误

     

Bank.java:33：错误：找不到符号bank.BankAccount.adjust（）;   符号：可变BankAccount位置：类型的可变银行   BankAccount [] 1个错误

BankAccount.class

public class BankAccount {

String owner; // owner of account
int accountNumber; // integer account number
double balance = 0.0; // account balance
double amount; // adjusted amount to balance
String balanceFmt = "%.2f"; // string format for 2 decimal places

public BankAccount(String owner, int accountNumber) { //Constructor for the bank account
   this.owner = owner;
   this.accountNumber = accountNumber;
}

public double adjust(double amount) { //method to adjust balance
   this.balance += amount;
   return balance;
}
public String toString() { // method to print out account info
   return owner + " owns the account " + accountNumber + " with the balance of $" + String.format(balanceFmt,balance);

}
public double getBalance() { // method to get balance of accounts
   return balance;   
}
}

Bank.class

public class Bank {

BankAccount bank[];

public Bank() { // constructor for making a 10 account array
   bank = new BankAccount[10];
}

public void addAccount(BankAccount accounts) { // add account for giving numbers to accounts
   for(int i = 0; i < bank.length; i++) {
      if(bank[i] == null) {
         bank[i] = accounts;
         break;
      }
   }
}

BankAccount getAccount(int i) { //obtain account from BankAccount class
   return bank[i];
}

public void printAccounts() { //prints out account statuses
   for(int i = 0; i < bank.length; i++) {
      if(bank[i] != null) {
      System.out.println(bank[i]);
      }
   }
}

public void monthlyFee(double fee) { //monthly fee for bank accounts
   for(int i = 0; i < bank.length; i++) {
      if(bank[i] != null) {
      } //I have tried BankAccount.adjust() and couldn't work, bank[i].adjust() nothing seems to work
   }
}
}

BankTest.class

public class BankTest { 
/*
 * test - set up a bank and add accounts
 */

public static void main(String[] args) {
// Code to test Bank and BankAccount classes
int errors = 0;
double fee = -2.95;

Assignment assignment = new Assignment();
assignment.homework("Homework 2a");

System.out.println("\nCreate bank1");
Bank bank1 = new Bank();
System.out.println("\nOne account");
BankAccount bankAccount1 = new BankAccount("Joe Mac", 1234);
bankAccount1.adjust(1000.0);
bank1.addAccount(bankAccount1);
bank1.printAccounts();
System.out.println("\nTwo accounts");
BankAccount bankAccount2 = new BankAccount("Sally Ride", 2345);
bankAccount2.adjust(2000.0);
bank1.addAccount(bankAccount2);
bank1.printAccounts();
System.out.println("\nThree accounts");
BankAccount bankAccount3 = new BankAccount("Pat Armstrong", 3456);
bankAccount3.adjust(3000.0);
bank1.addAccount(bankAccount3);
bank1.printAccounts();
System.out.println("\nMonthly Fee");
bank1.monthlyFee(fee);
bank1.printAccounts();
System.out.println("\nErrors:");

if (bank1.getAccount(0).getBalance() != 997.05) {
    errors += 1;
    System.out.println("Balance for account at index 0 does not match $997.05");
}
if (bank1.getAccount(1).getBalance() != 1997.05)
{
    errors += 1;
    System.out.println("Balance for account at index 1 does not match $1997.05");
}
if (bank1.getAccount(2).getBalance() != 2997.05)
{
    errors += 1;
    System.out.println("Balance for account at index 2 does not match $2997.05");
}
if (errors == 0)
    System.out.println("No errors found!!!");
}
}

非常感谢您的帮助和指导。谢谢。

Answer 1

简单：检查测试代码时，发现调用 adjust（）方法时，它传递一个双精度值！

您的其他代码（导致错误的代码）在调用该方法时似乎未传递任何双精度值！

Answer 2

似乎您忘记了传递费用参数来调整（）方法。以下代码可以很好地工作

 public void monthlyFee(double fee) { //monthly fee for bank accounts
    for(int i = 0; i < bank.length; i++) {
      if(bank[i] != null) {
        System.out.println(bank[i].adjust(fee));
      } //I have tried BankAccount.adjust() and couldn't work, bank[i].adjust() nothing seems to work
    }
  }

创建bank1

一个帐户 Joe Mac拥有帐户1234，余额为$ 1000.00

两个帐户 Joe Mac拥有帐户1234，余额为$ 1000.00 Sally Ride拥有帐户2345，余额为$ 2000.00

三个帐户 Joe Mac拥有帐户1234，余额为$ 1000.00 Sally Ride拥有帐户2345，余额为$ 2000.00 Pat Armstrong拥有帐户3456，余额为$ 3000.00

月费 997.05 1997.05 2997.05 Joe Mac拥有帐户1234，余额$ 997.05 Sally Ride拥有帐户2345，余额为$ 1997.05 Pat Armstrong拥有帐户3456，余额为$ 2997.05

错误：

未找到错误！