Solved–Lab #3– Solution

Description

Objectives

To practice implementing inheritance in Java.

To learn about the Object superclass and the methods it contains.

Code quality

The code you submit should be easily readable, clean and well-commented. Commented-out sections of non-working code should be removed. Indentations and white spaces should be used to separate

logical blocks of the code. Variables, methods and classes should have descriptive names.

Every class and method should have a comment according to Javadoc format (see Zybook).

When overriding methods, use @Override compiler annotation.

Square and Object

1. Download your code from last week’s Rectangle class and use it in this exercise. Refer to Zybook for examples to how to implement inheritance in Java.

2. Add toString() method of the Rectangle class so that it displays the information about the Rectangle object in a user-friendly way (i.e. it informs the user about the fact that it is a rectangle, and about its dimensions).

3. Make another class, Square, that is a subclass of Rectangle. The Square constructor should only take one size argument. Think about what can be directly inherited from the Rectangle class and what needs to be overwritten.

4. Override the toString method of the Rectangle class so that it displays the information about the Square object in a user-friendly way and informs the user about the fact that the object is a square, and about its dimensions.

5. Make a separate class, SquareTester to test the functionality of the above class. Create a square, print out the information about it using toString method, calculate and display its area and perimeter.

6. Look online at http://docs.oracle.com/javase/8/docs/api/java/lang/Object.html to read about Java’s Object class. Every class in Java is a subclass of Object. Browse the various methods that the Object class de nes. Do not worry about understanding what every method does.

7. In the Square class, override the equals method. The default equals method only returns true if the two objects are the same. For the Square class, two squares should be equal if they have the same size. The equals method takes an

Object as its argument. If your Object parameter is Object obj, you can cast it to a Square by using code such as: Square s = (Square) obj;. Before doing this, you should make sure that your Object is indeed a Square. To do this, you can use the instanceof method. Finally, you can now test the equality of the sizes of the squares.

8. Now in the SquareTester class from above, make two rectangles of the same size and two squares of the same size. Test the rectangles for equality using == and equals. Now do the same for the squares. Print out the results.

Bank Account

1. Create a class BankAccount. An object of this class should have a person’s name and a balance, stored as a double. Create methods getName and getBalance, and create deposit and withdraw methods to add and subtract a speci ed amount from the balance. Furthermore, create a transfer method, that takes another BankAccount and a speci ed amount, and transfers that amount from the original BankAccount to the one that is given. Finally, create a toString method that gives the name and balance of the account.

2. Now create another class named SavingsAccount. This should be a subclass of BankAccount. A SavingsAccount should have an interest rate that is speci ed in its constructor. Furthermore, there should be a method, addInterest, that deposits interest into account, based on the account balance and interest rate.

3. Create another subclass of BankAccount named CheckingAccount. A CheckingAccount should keep track of the number of transactions made (deposits and withdrawals). Name this eld transactionCount. Also, the set fee for transactions is three dollars, so create a static final eld, TRANSACTION FEE, that is set to 3.0. Finally, create a method, deductFees, that deducts fees from the account balance based on the number of transaction. This method should reset the transactionCount to zero.

4. Now make a class BankAccountTest with a main method to test the above classes. Create a SavingsAccount with zero balance, a 1% interest rate, and a name of your choice. Also create a CheckingAccount with a $500 initial balance and a name of your choice. Deposit $1000 into the SavingsAccount. Withdraw $100 from the CheckingAccount. Now transfer $200 from the SavingsAccount to the CheckingAccount. Print out both accounts. Now add interest to the SavingsAccount and deduct fees from the CheckingAccount. Print out both accounts and make sure the balances are as expected.