CSC 241- Exam 1 (October 4, 2002) Name:

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Consider the following Balance and bankAccount class skeletons for the first five questions:

public class Balance {
 private double amt;
 public Balance() {…}
 public void add(double a) {…}
 public void subtract(double a) throws negativeBalanceException {…}
 public double balance() {…}
}
 
public class bankAccount {
 private int accountNumber;
 private String name;
 private Balance b;
 public bankAccount(int an, String n) {…}
 public void deposit (double am) {…}
 public void withdrawal (double am) throws negativeBalanceException {…}
public double currentBalance() {…}
}
 

(20 Points) 1.

Examine the following code segments for legal and illegal uses of the classes Balance and bankAccount, their objects, and their components in an application that imports them. Assume that Balance x= new Balance(); and bankAccount y= new bankAccount(1234,"Jones"); already exist in an application. Clearly mark each as valid or invalid, when invalid, give a brief explanation.

1. y.name( )=new String("Smith");
2. if (x.amt = = y.currentBalance())
3. bankAccount t = new bankAccount(1,"Jones");
4. y.deposit(100.0);
5. y = new Balance( );
6. System.out.println("The current amount in Account is: " + y.currentBalance());
7. System.out.println("The name of the owner of the account is: " + y.name);
8. y.setAmount(100.0);
9. try {y.withdrawal(x);} catch (Exception e){}
10. try {x.subtract(10.0);} catch (Exception e){}

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(10 Points) 2. True/False:

a. String is a class in Java API.

b. int is a primitive type in Java like float or char.

c. java.awt is the package in Java API providing you with the graphical user interface components.

d. Applets run in a web browser.

e. The qualifier private put on a field or method allows it to be accessed outside of that class.

Here is the skeleton of the parkingLot class:

public class parkingLot {

public static final int capacity=100;

protected int carCount_;

protected String name_;

public parkingLot(String n) {…}

public int carCount () {…}

public String name () {…}

public void enter () throws parkingLotOverFlowException {…}

public void exit () throws parkingLotUnderFlowException {…}

public class parkingLotUnderFlowException extends Exception {…}

public class parkingLotOverFlowException extends Exception {…}

}

(30 Points) 3. INSIDE

I want you to add two methods to the parkingLot class. In each case think about the following before writing any code:

• Should the method be qualified as public, private, or protected?
• Should the method have a return type (a primitive or Object type) for a return value or does it need to be void?
• Does the method need any parameters; information sent to it by the caller?
• Should the method throw an exception?

1. Write a complete method named makeEmpty that makes the parkingLot empty. Write the post-condition for this method.

2. Write a method named empty that returns a boolean true if the parkingLot is empty and false otherwise.

(30 Points) 4. OUTSIDE

Assume that we are writing an application; you have no access to the protected components of a parkingLot. Answer the following:

a. Write a code segment that declares a parkingLot variable p_ and binds it with a new parkingLot named "SNYGG".

b. Write a code segment that increases the car count of p_ by 5. Think about how you can increase car count in this context.

c. Complete the method below that fills up a parkingLot to capacity. Use a while loop and as long as the parkingLot is not filled to capacity perform enter operations on it.

public static void fillUp (parkingLot p) {

}