类运算符错误数组：所需的意外类型：找到的变量：值

Question

I have an array of the BankAccount class and nested classes, including AccountInfoPrv with the method getAcctBalance(). The error occurs at the last line, where I call the BankAccount method getAccountInfoPrv() which then goes into the AccountInfoPrv class to call getAcctBalance(). It returns whatever value is there at index i, i've tested this without the operator in main method and it returns the value perfectly.. i'm not sure what i did wrong here.

Also, there is a lot of other code involved in this method but i tried to simply it with just this for loop.

  public static void withdrawal(Scanner kybd, BankAccount[] 
  account, int num_accts)
 {

 double amountToWithdraw;
 amountToWithdraw = kybd.nextDouble();

 for(int i=0; i<num_accts; i++)
 account[i].getAccountInfoPrv().getAcctBalance() -= 
 amountToWithdraw;
 }

Expected to subtract withdrawal amount from the value of account[i] and set account[i] to the new value.

Output: Error: unexpected type required: variable found : value

Answer 1

What you are trying to do over here is modify the "Value" returned by the getter method. In order to perform any such operation on the value returned by getter method, you would

1. First need to store it into a variable,
2. and modify its value,
3. and then call the setter to set the updated value in the object.

ie

balance = account[i].getAccountInfoPrv().getAcctBalance();
balance -= amountToWithdraw;
account[i].getAccountInfoPrv().setAcctBalance(balance);

In case of non-primitive type, calling setter explicitly is not required as it would get updated via reference.

Answer 2

Here you try to change from a getter (the method) it is not allowed. Try

account[i].getAccountInfoPrv().setAcctBalance(account[i].getAccountInfoPrv().getAcctBalance() - amountToWithdraw);