Module Contact: Dr Taoyang Wu, 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 FOR NON-SPECIALISTS CMP-5020B 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-5020B Module Contact: Dr Taoyang Wu, CMP Copyright of the University of East Anglia Version 1

2 Page 2 SECTION A 1. (a) Consider the following Java variables: a local variable of data type int and name age; a field of data type boolean and name isfree; a field of data type char and name vowel; a field called names and consisting of an array whose elements are of type String; (i) Provide a declaration for each of the items above. (ii) Which of the above types are primitive types? (b) Distinguish between a class and an object in Java. [2 marks] (c) A static method called numberofitems has two parameters. The first one corresponds to the cost of one item of a product, and the second to the amount of money that is available to a customer 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. [5 marks] (ii) Give a Java code fragment that uses your method to determine the number of items that may be purchased for 70 given that the cost per item is 13.45, and prints out this value. 2. (a) (i) Give a Java statement to define a constant identifier representing the number of hours worked in a normal working week (37.5 hours). (ii) Suppose workershours is an array whose elements are of type double and represent the number of hours worked during a particular week. Write a fragment of Java code to determine the number of workers who worked overtime during that week. (b) Distinguish between an array and an ArrayList in Java. CMP-5020B Version 1

3 Page 3 (c) Let HireCar be a Java class. Give a Java statement to create an ArrayList of HireCar objects called carfleet. (d) Suppose that the HireCar class contains a method with the header public boolean isavailable() which returns true if this HireCar is currently available for hire and false otherwise. Give a fragment of Java code to determine the number of HireCar objects available for hire in carfleet. 3. Explain what is meant by each of the following terms in the context of Java programming: (a) Java virtual machine; (b) javadoc; (c) static method; (d) visibility modifier; (e) method overloading; (f) interface (e.g. the Comparable interface); (g) method overriding. [2 marks] [2 marks] [2 marks] CMP-5020B Version 1 TURN OVER

4 Page 4 4. (a) Give the structure of a class defining a new type of object. [5 marks] (b) For each member of a sports club the following data is held: name (e.g. "Mark Smith"); contact details; year of birth (e.g. 1985); year of joining the club (e.g. 2008); type of membership (either F for family or P for personal). Let Member be a Java class with fields for each of the above data items. In addition, the class Member includes a class variable to keep track of the total number of members, and two class constants, one for the family subscription rate (150 pounds) and the other for the personal subscription rate (100 pounds). (i) Write a skeleton declaration for the class Member, to include definitions for the above fields, class variable and class constants, but no constructors or other method definitions. Assume that a class called ContactDetails has already been written and is available. (ii) Write a constructor for the Member class, with explicit arguments to define the initial values of the instance variables corresponding to the five fields specified above. You are not required to include any data error-checking. CMP-5020B Version 1

5 Page 5 (iii) Assume that the class ContactDetails contains a method specified as follows: /** * A method to change the address in this ContactDetails newaddress the address to which the address in * this ContactDetails is to be changed. */ public void setaddress(string newaddress) Write a mutator method for the class Member to update the address of a member, given a String representing the member s new address. (iv) Write an accessor method to determine the subscription due for a member. CMP-5020B Version 1 TURN OVER

6 Page 6 SECTION B 5. (a) Write a brief explanation of each of the following kinds of error: (i) compile-time error; (ii) run-time error; (iii) logical error. (b) Consider the following Java code: abstract public class Employee { protected String name; protected String address; public Employee(String aname, String anaddress){ name = aname; address = anaddress; } public String tostring(){ String resultstring = "Name: " + name + "\n"; resultstring += "Address: " + address; return resultstring; } public abstract double monthlypay(); } (i) Using Employee as a base class, define a non-abstract derived class called HourlyEmployee which has two additional fields, one for the hours worked per month (an integer) and one for an hourly rate of pay ( a double). Make use of super in both the constructor and the tostring method for HourlyEmployee. [15 marks] (ii) Define a second non-abstract derived class of Employee called StaffEmployee which has just one additional field, for a staff employee s annual salary (a double); [13 marks] CMP-5020B Version 1

7 Page 7 6. (a) 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 the status of a LibraryBook. (ii) Write a constructor for the LibraryBook class with explicit arguments to define the instance variables corresponding to the author and title fields. (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.) [8 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. [5 marks] CMP-5020B Version 1 TURN OVER

8 Page 8 (b) Assume that we have the following classes: Vehicle, Car, Truck, Motorbike, FourDoor, TwoDoor and MoPed. Car, Truck and Motorbike are each subclasses of Vehicle. FourDoor and TwoDoor are subclasses of Car and MoPed is a subclass of Motorbike. (i) Draw the inheritance hierarchy for the above classes. (ii) Which of the following assignments are legal and why? (1) Vehicle v1 = new Motorbike(); (2) Truck t = new Vehicle(); (3) Vehicle v2 = new MoPed(); (4) Car c = new TwoDoor(); (5) v1 = c; [9 marks] END OF PAPER CMP-5020B Version 1