Object-oriented programming (OOP) Questionbank

Full details of the customers are stored as objects of the Customer class. This class is partially shown below:

public class Customer
{
private String memberId;
private String email; //email address (assume only 1 per customer)
public Customer(String a, String b)
{
memberId = a;
email = b;
}
public String getMemberId()
{
return memberId;
}
public String getEmail()
{
return email;
}
}

The objects can be accessed through the linked list allCustomerswhich is declared in the main (driver) class as follows:

LinkedList<Customer> allCustomers = new LinkedList<Customer>()

A smartphone app is being developed to manage tasks and reminders. The app uses classes such as Task, Reminder, and Event, which inherit from a base class ScheduleItem.

A generic Event class is defined as follows:

class Event
{
private String eventID;
private int numberOfRaces;
private Race$$ races;
private Race finals;
public Event(String ID, int numberOfRaces)
{
eventID = ID;
races = new Race$numberOfRaces$;
for(int i = 0; i < numberOfRaces; i++)
{
races$i$ = new Race();
}
finals = new Race();
}
public void addSwimmers()
{
// fills the qualifying heats with swimmers
}
public void fillFinals()
{
// fills the finals race with the best 8 from the qualifying heats
}
// more methods()
}

The Event class above assumes that the event has more than 8 swimmers and requires qualifying heats. However, an event with less than 9 swimmers has no qualifying heats, so the original Event class was inherited by a new class FinalsOnlyEvent.

An image processing software needs to perform operations on a collection of pixels.

An airline company is updating its reservation system, which includes classes like Seat, EconomySeat, and BusinessSeat. EconomySeat and BusinessSeat inherit from Seat.

In a text processing program, we need to count the occurrences of a specific character.

A company provides car parking services in large cities and needs a computer system to keep track of the number of vehicles using its parking areas.

When a vehicle arrives, its registration plate is recorded on the system and it is allocated a number that identifies where it should park. When the vehicle leaves, that space is made available for other vehicles to use.

Vehicles are identified by their unique registration plate, which is an alphanumeric code of eight characters (e.g. X1234567). This is clearly displayed on the vehicle.

A programmer created the classes ParkingAreaandVehicleto model the above situation.

public class ParkingArea {  
private Vehicle vehicles$$;  
private String name;  

ParkingArea(String name, int capacity) {  
    this.name = name;  
    if (capacity > 300) capacity = 300;  
    this.vehicles = new Vehicle$capacity$;  
}  

String getName() {  
    return name;  
}  
  
public int getCapacity() {  
    return vehicles.length;  
}  

public int findVehicle(String reg) {  
    //find where the vehicle is located in the array and  
    //return the index not yet written  
}  
}

public class Vehicle {  
private String registration;  
private byte colour;  
private boolean broken;  

public final static byte BLACK=1;  
public final static byte WHITE=2;  
public final static byte BLUE=3;  
public final static byte RED=4;  
public final static byte GREEN=5;  
private final static double ADMIN\_FEE = 3;  

public Vehicle() {}  

public Vehicle(String registration) {  
    this.registration = registration;  
}  
public Vehicle(String registration, byte colour) {  
    this.registration = registration;  
    this.colour=colour;  
}  
public void setBroken(boolean broken) {  
    this.broken=broken;  
}  
public void setColour(byte colour) {  
    this.colour=colour;  
}  
public boolean getBroken() {  
    return broken;  
}  
public String getRegistration() {  
    return registration;  
}  
public double pay(int hours) {  
    // code to return admin fee - only if applicable  
}  
}

A hotel chain has a loyalty scheme in which customers are awarded 1000 points for each day they stay in one of their hotels. With these points, customers can achieve one of three status levels: Gold, Silver or Bronze. The level will determine the extra services to which they are entitled.

The total number of points collected during the current year will determine which of the three status levels they are assigned for the following year: For example only the points collected in 2018 will determine the status level for 2019.

Occasionally, new customers receive additional bonus points as part of a promotion.

The Pointsclass keeps details of the points and status levels of each customer.

public class Points
{
private String memberId; // id of the hotel customer
private int totalPoints; // this year's points
private int bonusPoints; // any bonus points given to this year's new member
private String statusNow; // current(this year's)status
private String statusNextYear; // following year's status
private Visits$$ allVisits = new Visits$366$;//details of each visit
// during this year
int y; // number of visits this year
public Points(String id) // constructor for new member
{
memberId = id;
bonusPoints = 0;
y = 0;
statusNow = 'Bronze';
}

//constructor for new member given bonus points (valid for current year only)
public Points(String id, int bp)
{
memberId = id;
bonusPoints = bp; // multiples of 1000 - maximum number is 5000
y = 0;
statusNow = 'Bronze';
}

// all the accessor and mutator methods are present but not shown
public Visits getAllVisits(int v)
{
return allVisits$v$;
}
public void addVisit(Visits v) // adds a new Visit object to the array
{
allVisits$y$ = v;
y = y + 1;
}

isGold() {code missing}
calculateTotalPoints(){code missing}
daysMissing(){code missing}
}

The instance variables in the Pointsclass are preceded by the modifier private. The choice of modifier affects the way in which these variables are accessed or used.

The customers will be assigned one of three levels for the following year (Gold, Silver or Bronze) depending upon the current year’s total points as follows.

• Bronze = less than 10 000 points
• Silver = 10 000 or more but less than 50 000
• Gold = 50 000 or more.

In 2018, Tim became a member for the first time and was awarded a bonus of 1000 points. So far, in 2018, Tim has stayed three times at one of these hotels. The first visit lasted 2 days, the second visit lasted 1 day and the third visit lasted 6 days.

The different Pointsobjects are stored in an array which is declared globally in the main (driver) class as follows:Points[] allPoints = new Points[10000];

A text editor needs to implement an undo functionality using stacks.

A restaurant uses an object-oriented program to manage the cost of the food and drink consumed by customers. Everytime a table is occupied a Paymentobject is instantiated which will contain details of the items ordered. As each item is ordered, a FoodItemor a DrinkItemobject is added to the Paymentobject as appropriate.

public class Payment
{
private FoodItem[] fi = new FoodItem[100];
private int fiCount;
private static double foodTax = 0.2; // 20 % sales tax added to
// all food prices
private DrinkItem[] di = new DrinkItem[100];
private int diCount;
private static double drinkTax = 0.1; // 10 % sales tax added to
// all drink prices
public Payment()
{
fiCount = 0;
diCount = 0;
}
public DrinkItem getDi(int x)
{
return di[x];
}

// all other accessor and mutator methods are included

// addFoodItem() – this method adds a new FoodItem object
// addDrinkItem() – this method adds a new DrinkItem object

public static double findPrice(Item[] pl, String c)
{ //code missing }

// calculateBill() – This method returns the bill (the total value of
// the items consumed for a particular table)
}

public class FoodItem
{
private String itemCode;
private int quantity;

public FoodItem(String x, int y)
{
itemCode = x;
quantity = y;
}
// all accessor and mutator methods are included
}

The DrinkItemclass is defined in a similar way.

Whenever a Payment object is instantiated, the variables fiCount and diCount are initialized to 0 through the code in the constructor.