Question

Look at the Account class below and write a main method in a different class to briefly experiment with some instances of the Account class.

Using the Accountclass as a base class, write two derived classes called SavingsAccountand CurrentAccount.ASavingsAccountobject, in addition to the attributes of an Account object, should have an interest variable and a method which adds interest to the account. ACurrentAccount object, in addition to the instance variables of an Account object, should have an overdraft limit variable. Ensure that you have overridden methods of the Accountclass as necessary in both derived classes.

Now create a Bankclass, an object of which contains an array of Account objects. Accounts in the array could be instances of the Account class, the SavingsAccountclass, or the CurrentAccount class. Create some test accounts (some of each type).

Write an update method in the bankclass. It iterates through each account, updating it in the following ways: Savings accounts get interest added (via the method you already wrote); CurrentAccounts get a letter sent if they are in overdraft.

The Bank class requires methods for opening and closing accounts, and for paying a dividend into each account.

Hints:

• Note that the balance of an account may only be modified through the deposit(double) and withdraw(double) methods.

• The Account class should not need to be modified at all.

-----------------------------------------------------------------------

Account.java :

/**

A class for bank accounts.

This class provides the basic functionality of accounts.

It allows deposits and withdrawals but not overdraft

limits or interest rates.

@author Stuart Reynolds ... 1999

*/

public class Account

{

private double bal;//The current balance

private int accnum;//The account number

public Account(int a)

{

bal=0.0;

accnum=a;

}

public void deposit(double sum)

{

if (sum>0)

bal+=sum;

else

System.err.println("Account.deposit(...):"

+"cannot deposit negativeamount.");

}

public void withdraw(double sum)

{

if (sum>0)

bal-=sum;

else

System.err.println("Account.withdraw(...): "

+"cannot withdraw negativeamount.");&nbsõbpx.øi5/p>

}

public double getBalance()

{

return bal;

}

public double getAccountNumber()

{

return accnum;

}

public String toString()

{

return "Acc "+ accnum + ": " + "balance = " + bal;

}

public final void print()

{

//Don't override this,

//override the toStringmethod

System.out.println(toString() );

}

}

Answer 1

// Account.java

public class Account {
   private double bal; // The current balance
   private int accnum; // The account number
  

   public Account(int accNo,double bal) {
       this.bal = bal;
       accnum = accNo;

   }

   public void deposit(double sum) {
       if (sum > 0)
           bal += sum;
       else
           System.out.println("Account.deposit(...): "
                   + "cannot deposit negative amount.");
   }

   public void withdraw(double sum) {
       if (sum > 0)
           bal -= sum;
       else
           System.out.println("Account.withdraw(...): "
                   + "cannot withdraw negative amount.");
   }

   public double getBalance() {
       return bal;
   }

   public int getAccountNumber() {
       return accnum;
   }

   public String toString() {
       return "Acc " + accnum + ": " + "balance = " + bal;
   }

   public final void print() {
       // Don't override this,
       // override the toString method
       System.out.println(toString());
   }

}

===================================

// SavingsAccount.java

public class SavingsAccount extends Account {
// Declaring instance variables
   private double annualInterest;

   // Parameterized constructor
   public SavingsAccount(int accNO, double balance, double rate) {
       super(accNO, balance);
       this.annualInterest = rate;
   }

   public double getAnnualInterest() {
       return annualInterest;
   }

   public void setAnnualInterest(double annualInterest) {
       this.annualInterest = annualInterest;
   }

   @Override
   public void deposit(double amt) {

       super.deposit(amt);

   }

   @Override
   public void withdraw(double amt) {
       if (getBalance() > amt)
           super.withdraw(amt);
   }

   public double monthlyInterestRate() {
       return annualInterest / 12;
   }

   public double getMonthlyInterest() {
       return getBalance() * (monthlyInterestRate() / 100);
   }

   public void addInterest() {
       super.deposit(getMonthlyInterest());

   }

   @Override
   public String toString() {
       return super.toString() + " Annual Interest: " + annualInterest;
   }

}

===================================

// CheckingAccount.java

public class CheckingAccount extends Account {
   private double creditLimt;

   // Parameterized constructor
   public CheckingAccount(int accNO, double balance, double creditLimit) {
       super(accNO, balance);
       this.creditLimt = creditLimit;
   }

   // Implementing the deposit method
   @Override
   public void deposit(double amt) {
       super.deposit(amt);
   }

   // Implementing the withdraw method
   @Override
   public void withdraw(double amt) {
       if (getBalance() >= amt)
           super.withdraw(amt);
   }

   @Override
   public String toString() {
       return super.toString() + " Credit Limt: " + creditLimt;
   }

}

=====================================

// Bank.java

public class Bank {
   private int limit;
   private Account accounts[] = null;
   private int cnt;
   private static int NEXTACCNO = 101;

   public Bank(int limit) {
       this.limit = limit;
       accounts = new Account[limit];
       this.cnt = 0;
   }

   public void openSavingsAccount(double bal, double rate) {
       if (cnt != limit) {
           accounts[cnt] = new SavingsAccount(NEXTACCNO, bal, rate);
           NEXTACCNO++;
           cnt++;
       }
   }

   public void openCheckingAccount(double bal, double creditLimit) {
       if (cnt != limit) {
           accounts[cnt] = new CheckingAccount(NEXTACCNO, bal, creditLimit);
           NEXTACCNO++;
           cnt++;
       }

   }

   public void printAccounts() {
       for (int i = 0; i < cnt; i++) {
           System.out.println(accounts[i]);
       }

   }

  
   public void deposit(int accNo,double amt)
   {
       int indx=-1;
       for(int i=0;i        {
           if(accounts[i].getAccountNumber()==accNo)
           {
               indx=i;
           }
       }
       if(indx!=-1)
       {
           accounts[indx].deposit(amt);
       }
   }
   public void withdraw(int accNo,double amt)
   {
       int indx=-1;
       for(int i=0;i        {
           if(accounts[i].getAccountNumber()==accNo)
           {
               indx=i;
           }
       }
       if(indx!=-1)
       {
           accounts[indx].withdraw(amt);
       }
   }
  
   public void addInterest(int accNo)
   {
       int indx=-1;
       for(int i=0;i        {
           if(accounts[i].getAccountNumber()==accNo)
           {
               indx=i;
           }
       }
       if(indx!=-1 && (accounts[indx] instanceof SavingsAccount))
       {
           ((SavingsAccount)(accounts[indx])).addInterest();
       }  
   }
}

====================================

// BankDemo.java

public class BankDemo
{
public static void main(String[] args)
{
Bank tinyBank = new Bank(3); // create Bank that can hold 3 accounts
tinyBank.openCheckingAccount(100,20); // balance=100 credit limit = 20
tinyBank.openSavingsAccount(200, 0.05); // balance=200 interest=5%
tinyBank.openCheckingAccount(300,30); // balance=300 credit limit = 30
tinyBank.openSavingsAccount(400,0.05); // balance=400 interest=5%);
tinyBank.openCheckingAccount(400,40); // balance=400 credit limit = 40
tinyBank.openSavingsAccount(400,0.05); // balance=400 interest=5%);

tinyBank.printAccounts();
  
System.out.println("\ntinyBank.deposit(112,500)");
tinyBank.deposit(112,500);

System.out.println("\ntinyBank.withdraw(101,500)");
tinyBank.withdraw(101,500);
System.out.println("\ntinyBank.withdraw(101,110)");
tinyBank.withdraw(101,110);
System.out.println("\ntinyBank.addInterest(101)");
tinyBank.addInterest(101);

System.out.println("\ntinyBank.addInterest(102)");
tinyBank.addInterest(102);
System.out.println("\ntinyBank.withdraw(102,500)");
tinyBank.withdraw(102,500);
System.out.println("\ntinyBank.withdraw(102,200)");
tinyBank.withdraw(102,200);

System.out.println();
tinyBank.printAccounts();

}
}

=====================================

Output:

Acc 101: balance = 100.0 Credit Limt: 20.0
Acc 102: balance = 200.0 Annual Interest: 0.05
Acc 103: balance = 300.0 Credit Limt: 30.0

tinyBank.deposit(112,500)

tinyBank.withdraw(101,500)

tinyBank.withdraw(101,110)

tinyBank.addInterest(101)

tinyBank.addInterest(102)

tinyBank.withdraw(102,500)

tinyBank.withdraw(102,200)

Acc 101: balance = 100.0 Credit Limt: 20.0
Acc 102: balance = 0.008333333333325754 Annual Interest: 0.05
Acc 103: balance = 300.0 Credit Limt: 30.0