Question

In Java

Create an interface GainsInterest that contains two method signatures with public access modifiers for compound daily and interestAccrued that both return BigDecimal.

Create an abstract Account class and a SavingsAccount that derives from it using best programming practices. Define an account balance that is set in the constructor of SavingAccount and passed to the constructor of the Account. SavingsAccount should implement GainsInterest, but you do not need to provide implementation for those methods beyond defining the method inside in the class and returning BigDecimal.ZERO.

Answer 1

GainsInterest interface:

import java.math.BigDecimal;

public interface GainsInterest {
   //Two abstract methods
   BigDecimal compoundDaily();
   BigDecimal interestAccrued();
}

Account class:

public abstract class Account {
//Define an account balance
   Double accountBalance;
  
   //constructor of Account class
   Account(Double accountBalance){
       this.accountBalance = accountBalance;
   }
}

SavingsAccount class:

import java.math.BigDecimal;

public class SavingsAccount extends Account implements GainsInterest{

   //constructor of SavingAccount
   SavingsAccount(Double accountBalance) {
       //passing to the constructor of the Account.
       super(accountBalance);
   }

   //implementing GainsInterest methods
   @Override
   public BigDecimal compoundDaily() {
       return BigDecimal.ZERO;
   }

   @Override
   public BigDecimal interestAccrued() {
       return BigDecimal.ZERO;
   }
}