Module Contact: Dr Gavin Cawley, CMP Copyright of the University of East Anglia Version 1

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1 UNIVERSITY OF EAST ANGLIA School of Computing Sciences Main Series UG Examination PROGRAMMING 1 CMP-4008Y 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-4008Y Module Contact: Dr Gavin Cawley, CMP Copyright of the University of East Anglia Version 1

2 Page 2 SECTION A 1. (a) How is (i) a constant identifier, (ii) a class variable defined in Java? Give an example in each case. (b) Explain what is meant by a static method in Java. [6 marks] A static method called numberofitems is to have two parameters, the first corresponding to the cost of one item of a product and the second to the amount of money a customer has available for purchasing items of this product. The method is to return the number of items that may be purchased for the given amount. (i) Write Java code for the method numberofitems. (ii) Give a Java code fragment that uses your method to determine the number of items that may be purchased for 100, given that the cost per item is The code fragment must also print out this value. (c) In the context of Java: (i) explain the differences between primitive data types and reference types; (ii) distinguish between a class and an object. 2. (a) Give a Java statement to create a boolean array called vacant of size 25. (i) How is the last element of vacant indicated? [1 mark] (ii) Write a fragment of code to determine the number of elements of vacant that are equal to true CMP-4008Y Version 1

3 Page 3 (b) In the context of Java methods, distinguish between formal parameters and actual parameters. Describe what happens when a method is invoked in Java. [5 marks] (c) A static method, maxdigit, has a single formal parameter, n, of type int. This parameter may be assumed to be positive (i.e. n > 0). The method is to return the value of the biggest digit in n. For example, maxdigit( ) would return 7. Write Java code for the method maxdigit. [7 marks] 3. (a) In the context of Java, what does inheritance mean? (b) Given the following class public class Building{ protected int numrooms; protected int numfloors; } write a class House that inherits from Building, has an extra field for the number of bedrooms and a method that sets the number of bedrooms. (c) Describe the relationship between Building and House in a UML class diagram. (d) Suppose a class called Street contains a public collection of objects of type House called houses, a further private String field called name and a constructor that takes the number of houses and the street name as arguments. Represent this relationship as a UML class diagram, then implement the class Street. [8 marks] CMP-4008Y Version 1 TURN OVER

4 Page 4 4. (a) Give the structure of a class defining a new type of object. [5 marks] (b) A class Car has the following fields: private String registration; private int doors; private String colour; private CarDealer supplier; (i) Define a class variable, totalcars, whose purpose is to keep track of the total number of Car objects constructed during execution of a program that uses the Car class. (ii) Define a constructor for this class which has a formal parameter corresponding to each field. (iii) Define an accessor method called getcolour whose purpose is to return the value of the colour field of the Car. (iv) Assume that the class CarDealer has a method with the header public Address getlocation() which returns the address of a CarDealer object. Define an accessor method for the class Car called getdealeraddress whose purpose is to return the address of the dealer who supplied this Car. (v) Assuming that an equals method is defined in the CarDealer class, define a method for the Car class that determines whether or not this Car has been supplied by a given CarDealer. CMP-4008Y Version 1

5 Page 5 SECTION B 5. (a) Define what is meant by an algorithm. [5 marks] (b) State what is meant by a recursive algorithm. (c) When defining a recursive algorithm, what rules must you adhere to? (d) When is a recursive algorithm tail recursive? [5 marks] (e) Consider the following algorithm Algorithm: stringreversal(s) Given a character string, s, to output a string consisting of the characters in s but in reverse order n := length of s if ( n = 1 ) then return s else headofs := substring of s in character positions 1 to 1 tailofs := substring of s in character positions 2 to n return concatenation of stringreversal( tailofs ) and headofs endif (i) Is this algorithm tail recursive? Justify your answer. (ii) Give a non-recursive algorithm for solving the string reversal problem. [10 marks] CMP-4008Y Version 1 TURN OVER

6 Page 6 (f) Define a Java class called Sorting that contains a single static method implementing the following algorithm for sorting an unsorted array of Comparable objects. [10 marks] Given an array a = [a 1,a 2,...,a n ] of items to be sorted into ascending order. k := 1 for i from 1 to n 1 do next := a i indexofnext := i for j from i + 1 to n do if ( a j < next ) then next := a j indexofnext := j endif endfor swap the positions of item a i and next in the array endfor (g) A class Name implements the Comparable interface. Suppose facebookfriends is an unordered array of Names. Write a Java statement that uses your sort method to sort this array. CMP-4008Y Version 1

7 Page 7 6. Consider the following Java code: abstract public class Policy { protected String policynumber; protected int yearstarted; public Policy(int year, String policyno){ yearstarted = year; policynumber = policyno; } public String tostring(){ String resultstring = "Policy number: " + policynumber + "\n"; resultstring += "Year taken out: " + yearstarted; return resultstring; } public abstract double getpremium(); } (a) Explain what is meant by a base class and by a derived class in Java. Explain the meaning of the Java reserved word super. (b) Explain the significance of the key words abstract and protected as used in the above code. [5 marks] (c) Explain what is meant by the term method-overriding in Java. Does the above code exhibit method-overriding? Justify your answer. [5 marks] (d) Using Policy as a base class, define a non-abstract derived class called BuildingPolicy which has an additional field, for the cost (a double) of rebuilding the insured building. The premium for a BuildingPolicy is given by multiplying the rebuilding cost by a rebuilding factor defined by a class constant ( a double) set to Make use of super in both the constructor and the tostring method for BuildingPolicy. [12 marks] CMP-4008Y Version 1 TURN OVER

8 Page 8 (e) Define a second derived class of Policy called ContentsPolicy which has two additional fields, contentsvalue and riskfactor, both of which are of type double.contentsvalue represents the total value of the contents of the building whose contents are being insured. The premium for a ContentsPolicy is given by multiplying 1% of the value of the contents by 1+ the risk factor. [8 marks] (f) Explain how inheritance supports polymorphism in Java. Illustrate your answer using the above example. [6 marks] END OF PAPER CMP-4008Y Version 1