Question

Bank Accounts

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

• Using the Account class as a base class, write two derived classes called SavingsAccount and CheckingAccount. A SavingsAccount object, in addition to the attributes of an Account object, should have an interest variable and a method which adds interest to the account. A CheckingAccount object, in addition to the attributes of an Account object, should have an overdraft limit variable. Ensure that you have overridden methods of the Account class as necessary in both derived classes.

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

• The Bank class requires a method for opening accounts, and to deposit and withdraw from accounts specified by their account number. Account numbers are generated sequentially starting with 101.

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. • Be sure to test what you have done after each step.
• Use BankDemo.java to test your code.

Answer 1

package com.bank;
public class BankDemo
{
public static void main(String[] args)
{
Bank tinyBank = new Bank(10); // 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.printAccouns();
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.printAccouns();
}
}

----------
package com.bank;

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.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());
}

public void addInterest() {
}
}
---------------
/**
*
*/
package com.bank;

/**
* @author
*
*/
public class CheckingAccount extends Account {

int overDraftLimit;

/**
* @return the overDraftLimit
*/
public int getOverDraftLimit() {
return overDraftLimit;
}

/**
* @param overDraftLimit the overDraftLimit to set
*/
public void setOverDraftLimit(int overDraftLimit) {
this.overDraftLimit = overDraftLimit;
}

public CheckingAccount(int accNum, int b, int od) {
super(accNum);
super.deposit(b);
overDraftLimit = od;
// TODO Auto-generated constructor stub
}

}

---------
/**
*
*/
package com.bank;

/**
* @author
*
*/
public class SavingsAccount extends Account {

double interest;

/**
* @return the interest
*/
public double getInterest() {
return interest;
}

/**
* @param interest the interest to set
*/
public void setInterest(double interest) {
this.interest = interest;
}

public SavingsAccount(int accNum, int balance,double interest) {
super(accNum);
super.deposit(balance);
this.interest = interest;
// TODO Auto-generated constructor stub
}

}

----------
/**
*
*/
package com.bank;

/**
* @author
*
*/
public class Bank {

int accountNum = 100;
Account[] accounts = null;
int count = 0;

public Bank(int size) {
accounts = new Account[size];
}

public void openCheckingAccount(int i, int j) {
// TODO Auto-generated method stub
accounts[count++] = new CheckingAccount(accountNum++, i, j);
}

public void openSavingsAccount(int i, double d) {
// TODO Auto-generated method stub
accounts[count++] = new SavingsAccount(accountNum++, i, d);

}

public void deposit(int i, int j) {
// TODO Auto-generated method stub

for (int k = 0; k < count; k++) {
if (accounts[k].getAccountNumber() == i) {
accounts[k].deposit(j);
}
}

}

public void withdraw(int i, int j) {
// TODO Auto-generated method stub
for (int k = 0; k < count; k++) {
if (accounts[k].getAccountNumber() == i) {
if (accounts[k].getBalance() > j)
accounts[k].withdraw(j);
else
System.out.println("No sufficient balance");
}
}
}

public void printAccouns() {
// TODO Auto-generated method stub
for (int k = 0; k < count; k++) {

accounts[k].print();
;

}
}

public void addInterest(int i) {
// TODO Auto-generated method stub

for (int k = 0; k < count; k++) {
if (accounts[k].getAccountNumber() == i && accounts[k] instanceof SavingsAccount) {
double bal = accounts[k].getBalance();
double intRate = ((SavingsAccount) accounts[k]).getInterest();

double intrest = bal + ((bal * intRate) / 100);
accounts[k].deposit(intrest);
}
}

}

}

-------
Output
Acc 100: balance = 100.0
Acc 101: balance = 200.0
Acc 102: balance = 300.0
Acc 103: balance = 400.0
Acc 104: balance = 400.0
Acc 105: balance = 400.0

tinyBank.deposit(112,500)

tinyBank.withdraw(101,500)
No sufficient balance

tinyBank.withdraw(101,110)

tinyBank.addInterest(101)

tinyBank.addInterest(102)

tinyBank.withdraw(102,500)
No sufficient balance

tinyBank.withdraw(102,200)

Acc 100: balance = 100.0
Acc 101: balance = 180.04500000000002
Acc 102: balance = 100.0
Acc 103: balance = 400.0
Acc 104: balance = 400.0
Acc 105: balance = 400.0