Question

• The InterestBearingAccount interface declares a single method addInterest(no parameters, void return type) that increases the balance by the interest rate that is appropriate for the particular account.
• An InterestCheckingAccount is an Account that is also an InterestBearingAccount. Invoking addInterest increases the balance by 3%.
• A PlatinumCheckingAccount is an InterestCheckingAccount. Invoking addInterest increases the balance by double the rate for an InterestCheckingAccount (whatever that rate happens to be).
• A NonInterestCheckingAccount is an Account but it is not an InterestBearingAccount. It has no additional functionality beyond the basic Account class.

Hi, this program is in Java language. I have the Account class mostly done (there are some error messages). The Account class that those two classes are referring to is an abstract class. Furthermore, I believe the InterestBearingAccount (which is an interface) is being implemented by the Account class.

For the InterestBearingAccount interface, I currently have it as: return balance + (currentBalance * 3.00); but it is showing an error.

I believe for the NonInterestBearingAccount, there is nothing that needed to be added to it?

Will you be able to show me how you would implement these four classes?

Thank you.

Answer 1

Note: The question didn't ask for account class so I haven't created one instead I have fulfilled the instruction with only three classes

Program

interface InterestBearingAccount {//Interface for interest-bearing
   public void addInterest();
}

class InterestCheckingAccount implements InterestBearingAccount {
   private String name;
   private int accNumber;
   private double balance;
   private double interestRate;

   public InterestCheckingAccount(String name, int accNumber, double balance, double interestRate) {
       this.name = name;
       this.accNumber = accNumber;
       this.balance = balance;
       this.interestRate = interestRate;
   }

   public double getBalance() {
       return balance;
   }

   public double getInterestRate() {
       return interestRate;
   }

   @Override
   public void addInterest() {//calculating interest
       balance += balance * (interestRate / 100);
   }

   @Override
   public String toString() {//for showing account details
       return "Name= " + name + ", Account Number= " + accNumber;
   }
}

class PlatinumCheckingAccount implements InterestBearingAccount {

   private String name;
   private int accNumber;
   private double balance;
   private double interestRate;

   public PlatinumCheckingAccount(String name, int accNumber, double balance, double interestRate) {
       this.name = name;
       this.accNumber = accNumber;
       this.balance = balance;
       this.interestRate = interestRate*2;//doubling the checking account interest rate
   }

   public double getBalance() {
       return balance;
   }

   @Override
   public void addInterest() {
       balance += balance * (interestRate / 100);
   }

   @Override
   public String toString() {
       return "Name= " + name + ", Account Number= " + accNumber;
   }
}

class NonInterestCheckingAccount {//simple account
   private String name;
   private int accNumber;
   private double balance;

   public NonInterestCheckingAccount(String name, int accNumber, double balance) {
       this.name = name;
       this.accNumber = accNumber;
       this.balance = balance;
   }

   public double getBalance() {
       return balance;
   }

   @Override
   public String toString() {
       return "Name= " + name + ", Account Number= " + accNumber;
   }
}

public class Test {// driver class
   public static void main(String[] args) {
      
       InterestCheckingAccount obj = new InterestCheckingAccount("Daniel", 123, 1250.36, 3);//3% rate
       //sending checking account interest rate
       PlatinumCheckingAccount obj2 = new PlatinumCheckingAccount("Samantha", 124, 5236, obj.getInterestRate());
       NonInterestCheckingAccount obj3 = new NonInterestCheckingAccount("John", 125, 9650);
      
       //showing results
       System.out.println("******Checking Account******");
       System.out.println(obj);
       System.out.println("Balance before interest: "+obj.getBalance());
       obj.addInterest();
       System.out.println("Balance after interest: "+obj.getBalance());
       System.out.println("------------------------------");
      
       System.out.println("******Platinum Checking Account******");
       System.out.println(obj2);
       System.out.println("Balance before interest: "+obj2.getBalance());
       obj2.addInterest();
       System.out.println("Balance after interest: "+obj2.getBalance());
       System.out.println("------------------------------");
      
       System.out.println("******Non Interest Checking Account******");
       System.out.println(obj3);
       System.out.println("Balance: "+obj3.getBalance());
       System.out.println("------------------------------");
   }
}

Output