Module Contact: Dr Geoff McKeown, CMP Copyright of the University of East Anglia Version 1

Transcription

1 UNIVERSITY OF EAST ANGLIA School of Computing Sciences Main Series UG Examination PROGRAMMING FOR APPLICATIONS CMP-4009B Time allowed: 2 hours Section A (Attempt all questions: 80 marks) Section B (Attempt one question: 40 marks) Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. CMP-4009B Module Contact: Dr Geoff McKeown, CMP Copyright of the University of East Anglia Version 1

2 Page 2 SECTION A 1. (a) Which of the following are not valid Java identifiers, and why? (i) ManUtd (ii) man.utd (iii) sumofxandy (iv) 5star (v) _321 (b) Explain what is meant by a static method in Java. [5 marks] (c) The body mass index (bmi) is a measure of the effect of weight on health. It is calculated by taking a person s weight in kilograms and dividing this value by the square of the person s height in metres. The following table gives the health interpretations corresponding to ranges of bmi. bmi bmi < 16 interpretation seriously underwieght 16 bmi < 18 underweight 18 bmi < 24 normal weight 24 bmi < 29 overweight 29 bmi < 35 seriously overweight bmi 35 obese Write Java code for the body of a static method with header public static String bodymassindex(double weight, double height) which, given double values representing a person s weight and height, returns the corresponding health interpretation. [12 marks]

3 Page 3 2. (a) In the following pair of Java expressions, a, b, c and d are integers, isunder is boolean and the value of the constant BOUND is 24. a - (b - c)* d isunder && (a > b) c % BOUND < BOUND/5 (i) Draw an evaluation tree for each of these expressions. [6 marks] (ii) Use these trees to evaluate each expression, assuming a has value 33, b has value 27, c has value 14, d has value 3 and isunder has value true. [4 marks] (b) (i) Give Java code to define an array of n elements of type char, called grades. (ii) Assuming the elements of the array grades have been assigned values of type char, give Java code to determine the number of elements equal to a and the number of elements equal to b. [7 marks] TURN OVER

4 Page 4 3. (a) Give the structure of a class defining a new type of object. [5 marks] (b) A class Television has the following fields: private TelevisionManufacturer supplier; private String code; private int screensize; // in inches private String type; // e.g. plasma screen (You may assume that the class TelevisionManufacturer is available). (i) Define a class variable, totaltvs, whose purpose is to keep track of the total number of Television objects constructed during execution of a program that uses the Television class. [2 marks] (ii) Declare a default constructor for the Television class. (iii) Declare an accessor method called getscreensize whose purpose is to return the value of the screensize field of this Television. (iv) Declare a mutator method that sets the type of this Television to a given value. (v) Declare a method to determine whether or not this Television has been supplied by a given manufacturer. You should assume that the class TelevisionManufacturer contains an equals method. [4 marks]

5 Page 5 4. (a) In the context of Java methods, distinguish between formal parameters and actual parameters. Give an example to illustrate your answer. [8 marks] (b) Explain what is meant by each of the following terms in the context of Java: (i) instance variable; (ii) method overloading; (iii) base class; (iv) method overriding. TURN OVER

6 Page 6 SECTION B 5. (a) (i) Distinguish between an array and an ArrayList in Java. [6 marks] (ii) Suppose that a class ClientDetails is used to represent information about a client of a business. Give a Java statement to create an ArrayList called clientlist to represent a list of ClientDetails. (iii) Give a Java statement to assign the first client details in clientlist to a ClientDetails variable, first. [2 marks] (iv) Give an assignment statement assigning the number of clients in clientlist to a variable portfoliosize. [2 marks] (v) Now let givenclient be a ClientDetails variable representing some client. Assuming that the ClientDetails class contains an equals method, write a code fragment to determine whether or not givenclient is in clientlist. [7 marks]

7 Page 7 (b) A class LibraryBook has four fields: title, author, classification and status. The first three of these fields are of type String whilst status is of a user-defined type called BookStatus. At any time during its existence the status of a LibraryBook object is one of the following: reference only, on-loan or available for lending. (i) Define an enum type for a LibraryBook s status. [4 marks] (ii) Write a constructor for the LibraryBook class with explicit arguments to define the instance variables corresponding to the author and title fields. [5 marks] (iii) Write a method for the LibraryBook class to set the status of this LibraryBook to reference only, provided its status has not already been set. If the status of this LibraryBook has already been set an IllegalAttemptToSetStatusException should be thrown. (You may assume that the IllegalAttemptToSetStatusException class is available.) [7 marks] (iv) Write a boolean method for the LibraryBook class that returns true if the status of this LibraryBook is reference only, and false otherwise. [4 marks] TURN OVER

8 Page 8 6. (a) Describe what is meant by each of the following terms in the context of Java programming: (i) inheritance; (ii) polymorphism; (iii) dynamic binding. [6 marks] [6 marks] (b) Consider the following class Customer: public abstract class Customer{ protected String customerid; protected String customeraddress; public Customer(String custid, String address){ customerid = custid; customeraddress = address; } /** this customer s percentage discount for any purchase */ public abstract int getdiscountrate(); public String tostring(){ String resultstring = "Customer ID: " + customerid + "\n"; resultstring += "Customer address: " + customeraddress; return resultstring; } }

9 Page 9 (i) Write Java code for a class BusinessCustomer that inherits from Customer and has an additional field for the name of the business (a String) and another additional field for a fixed percentage discount (an integer) that this business customer is given on all orders. Make use of super in both the constructor and the tostring method for BusinessCustomer. Your solution should include an implementation of the getdiscountrate() method to override the abstract method in the Customer class. [10 marks] (ii) Define a second derived class of Customer called EducationalCustomer which has just one additional field, for the name of the educational institution (a String). Each educational institution receives a fixed discount on all orders. The supplier has currently set this value at 25%. [10 marks] (iii) Suppose that customerrecords is an array whose elements are of type Customer. Consider the following Java code fragment : for (Customer c : customerrecords) System.out.println(c.getDiscountRate()); Explain how execution of this code would result in polymorphic behaviour. [5 marks] END OF PAPER