DP Computer Science Questionbank

Define the term mutator method.

State one additional instance variable of type boolean which could be added to the class Race as indicated above.

With reference to both class UMLs provided above, distinguish between a class and an instantiation.

Many swimmers in the event have names that cannot be represented using basic character sets such as ASCII.

Describe one feature of modern programming languages that allows the wide range of students’ names to be represented correctly.

Outline one disadvantage of using aggregation in this context.

The same method identifier addSwimmers is used in both classes Race and Event.

Explain why this does not cause a conflict.

Outline how method overriding can help to create the new class FinalsOnlyEvent.

Construct the code fragment for the given situation that will copy swimmers and times into two parallel arrays named tempSwimmer and tempTime.

Outline one advantage of using aggregation in this context.

Construct code for the constructor of the class Swimmer that instantiates an object with parameters name and school. The event IDs should be set to “empty” and the times to 0.0

Outline two advantages of the OOP feature “inheritance”.

Sketch the resulting swimmer array in finals.

Construct the code fragment that will copy the names of the 8 fastest swimmers in ascending order of time from the array tempSwimmer to the array swimmers in the race finals.

Outline one reason why a linked list may be more suitable than a binary tree in this particular situation.

Construct the code needed to instantiate an object guests of the LinkedList class.

Define the term object reference.

Construct the code for the method penultimate() that returns the second to last element in the linked list guests. You may assume that guests is locally accessible.

Using the data provided in the diagram, trace the call recursive(0,'F'), clearly showing the levels of recursion.

Outline one reason why the use of a recursive method may be inappropriate for linked lists.

Due to unforeseen circumstances, schools may cancel their participation in an event at the last minute. Therefore, a method is needed to remove all the visiting students of one school from the linked list guests.

Construct the method removeSchool that takes the name of a school as parameter and removes all students of that school from the list guests.

State the implication of the use of the term static in the Payment class.

Outline an alternative method of initializing these variables that would not require the use of the code in the constructor.

The Payment class method addFoodItem() is passed a FoodItem object as a parameter.

Construct the method addFoodItem().

With reference to two examples from the classes in the resource, explain the benefits gained by the use of different data types.

Describe the purpose of the following statement:

private FoodItem[] fi = new FoodItem[100]

Construct statements, in code, that will print out the following: The number of drink items ordered by table 40.

State the output after this code is executed.

Construct statements, in code, that will print out the following: The item code of the third food item ordered by table 2.

The company that owns this restaurant also owns hotels, shops, and a car hire business. The programs that manage the finances of these different businesses include classes similar to the ones shown in this paper.

Explain how inheritance could be used as a tool to both improve the clarity of the design and to reduce the amount of code that needs to be written.

Construct the method findPrice(). You may assume that the item exists in the array.

When a customer wishes to pay the bill, the $\mathrm{calculateBill} ( )$ method is called. If the bill was for table 10 then the following call would be made:

double finalBill = tables[10].calculateBill(Item[] pl);

Construct the calculateBill() method. You should make use of any previously defined methods.

Construct a diagram showing the relationships between the Payment, FoodItem, DrinkItem, and Item classes. You do not need to include the names of attributes or methods.

By making reference to any of the classes from 12(a), describe two benefits that a programming team would gain from the use of encapsulation.

Construct the method changePrice().

The method palindrome() is called by boolean t = palindrome(word);
where word is a String variable.

Without writing code, describe the recursive method palindrome() that returns whether or not a word is a palindrome.

Outline one benefit that the use of either of these choices will have over the original array structures.

Explain how a binary tree structure would allow a more efficient search for the Item object.

Describe two disadvantages of using Object Oriented Programming (OOP).

State the relationship between the Flight object and the Arrival object.

Construct the method search implementing a linear search. Use the first compareWith() method in the Arrival object.

You may assume that an Arrival object with the given flightID exists in the array inbound.

Outline the use of data-hiding as a security feature in OOP.

Outline the general nature of an object.

Outline one advantage of using modularity in program development.

Construct a UML diagram to represent the Arrival object.

The Arrival object has two methods named compareWith.

Outline why calling the compareWith method does not cause a conflict.

Construct a method showDelayed() that outputs the IDs of all delayed flights in the array inbound that have not yet landed and that have an ETA before a given time t. The time t is passed as a String parameter.

When a flight is delayed, a method in FlightManagement is used to find and update the flight with the delay and to reorganize the array so that it remains sorted for the ETA.

Describe how this method would be implemented using the methods provided.

Sketch the resulting linked list when an airplane with ID RO225, STA 12:05 and delay 0 is added to this list.

In case of bad weather it is possible that one of the runways has to be closed and the two linked lists (runway1 and runway2) need to be merged using a method mergeLists() into one new linked list runway.

Construct the method public LinkedList<Arrival> mergeLists() that merges the two sorted linked lists in to one sorted linked list result which needs to be returned. You may assume that runway1 and runway2 are accessible to the method and do not need to be passed. The original two lists are allowed to become null as a result of the merging. 

In answering this question, you may use the following methods from the JETS LinkedList class, in addition to any method provided or developed in this exam paper.

addFirst(<object>)   // adds the object at the head of the list
addLast(<object>)    // adds the object at the tail of the list
getFirst()           // returns the head object in the list
getLast()            // returns the tail object in the list
removeFirst()        // removes and returns the head object
removeLast()         // removes and returns the tail object
size()               // returns the number of objects in the list
isEmpty()            // returns true if the list is empty

Define the term method signature.

Trace the call process(runway1,0) given the diagram of runway1 as drawn above. Copy and complete the following table.

Without using a sorting algorithm, construct the method add(Arrival newArrival) that inserts a newArrival in the sorted array inbound. You may assume that newArrival has been instantiated and that the array inbound is not full.

Evaluate the use of dynamic linked lists to static arrays when managing arriving airplanes.

Outline an advantage of using a library.

Distinguish between a class and an instantiation. You must make reference to the UML provided.

Define the term identifier.

State the code fragment that instantiates an array line of 20 Cart objects.

Explain one advantage of the OOP feature “inheritance” with reference to this scenario.

Define the term inheritance.

Outline two reasons why the use of multiple programming teams in different locations may be problematic when developing an integrated software solution.

Outline why the variable active in the UML of the class POSline was defined as a boolean data type.

Describe two advantages of using libraries of classes.

State the relationship between the POSsystem and POSline objects.

Construct the method public void joinLine(Cart newCart) that adds a newCart to line in the next empty array location. You may assume that line is not full.

Construct the code for a method split (part of the class POSsystem), that takes an existing, non-empty POSline as a parameter. It should copy every second cart from the original line into a new line. Afterwards it should delete every second cart from the original line.

An example call in POSsystem would be: POSline number2 = split(number1), where number1 is an existing POSline.

You may use any method declared or developed.

Draw a diagram to show the relationship between the objects POSsystem, POSline and Cart. You are not required to draw a complete UML diagram.

Construct the method public Cart leaveLine(int n) that removes the cart at position n from line by shifting down all the array entries bigger than n, before returning the indicated Cart object. You may assume that a cart exists at position n.

As a result of the simulation, the company has decided to create a new POS system for their supermarkets.

There have been discussions about adapting existing open source code when developing modules of the new POS system.

Describe two ethical issues that may arise if modules of the new POS system are developed from open source code.

Define the term object reference.

Using object references, construct the method public Cart removeFirst() that removes the first CartNode object from list. The method must return the Cart object in that node or null if list is empty.

Sketch the linked list list after running the following code fragment where cart1, cart2, cart3, cart4 and cart5 have been instantiated as objects of the class Cart.

POSlist queueList = new POSlist()
queueList.addLast(cart2);
queueList.addLast(cart1);
queueList.addLast(cart4);
queueList.removeFirst();
queueList.addLast(cart5);
queueList.addLast(cart3);
queueList.removeFirst();

Outline one feature of the abstract data structure queue that makes it unsuitable to implement customers waiting in line.

Using object references, construct the method public Cart leaveList(int n) that removes the nth CartNode object from list. The method must return the Cart object in that node.

You may assume that the nth CartNode object exists in the list.
You may use any method declared or developed.

Explain the importance of using coding style and naming conventions when programming.

Outline one effect of using the modifier static when declaring a variable.

Describe the relationship between the classes Vehicle and ParkingArea.

Construct code to create an instance of the Vehicle class that has a registration of X1234567.

Outline why it is necessary to use the keyword this in the setBroken method of the Vehicle class.

Construct code that sets the colour of the object created in part (i) as black.

Outline why searching for the registration plate in a binary tree would be faster than looking for it in the two-dimensional array.

Construct a UML diagram that shows the relationships between the ParkingArea, Vehicle, Motorbike and Car classes. There is no need to include the attributes or methods of each class.

Identify the steps that would be involved in taking the data from this two-dimensional array and creating a binary search tree.

A stack can be implemented using an array or a singly linked list.

Compare the use of these two data structures for creating a stack.

Outline two differences between inheritance and aggregation.

Construct the staffRemoveCar method.

Construct the method pay in the Vehicle class that returns the admin fee stored in the variable AdminFee if the vehicle has stayed for five hours or less; otherwise, it returns 0.

Construct the method pay in the Car class, where it uses the vehicle method pay but adds the charge for the amount of time spent in the parking area.

The array vehicles[] in the ParkingArea class is used to store instances of the Car or Motorbike class.

Outline why Vehicle is a valid type for this array.

Describe, without writing code, any changes required to the addVehicle method and the ParkingArea class to make the new voucher scheme work.

Identify three other tests you might perform on the completed code to prove that it functions correctly.

The removeVehicle method of the ParkingArea class searches in the array for a Vehicle object with a specified registration plate, then removes it by setting that array index to null.

The method returns a reference to the Vehicle object that has been removed from the array, or null if no matching registration plate was found.

Construct the removeVehicle method.

With the use of two examples other than private, outline how the choice of this modifier affects the way in which these variables are accessed or used.

With reference to the two methods with the same name in the Points class, explain the OOP feature that makes it possible to successfully implement either of these methods.

State the output given by the following statement:

System.out.println(allPoints[2].getMemberId());

State the output given by the following statement:

System.out.println(allPoints[1].getAllVisits(1).getDays());

Construct the method calculateTotalPoints(), in the Points class, which will calculate and return the total number of points awarded so far in the current year.

State the output given by the following statement:

System.out.println(allPoints[0].getBonusPoints());

State how an individual object can be identified using this array.

Construct a UML diagram for the Visits class.

The attribute statusNow is assigned its correct value at the beginning of every year for existing members. It cannot be changed during the year.

Construct the method isGold() in the Points class, which will return whether the current status is “Gold”.

Copy and complete the following table to show the output when the method is called by: recursionEx(3);

Construct the method goldMails() that will return an ArrayList containing the email addresses of all current “Gold” members. You should make use of any previously defined methods.

Identify two essential features of a recursive algorithm.

Explain what would happen if the method was called by recursionEx(-3).

Identify three features which should be included in either program code or UML diagrams to help programmers understand and modify programs in the future.