During the exam

You are not allowed to access any previously written documents or code files from your home drive or the web. If you do, it will be considered plagiarism.

As in a normal examination, communication between candidates during the laboratory exam is strictly forbidden.

Any candidate who experiences a hardware or software problem during the examination should summon an invigilator at once.

Overview

This exam consists of two parts: part 1 requires you to write a Python program, and part 2 requires    you to write a Java program. The instructions, allocated marks, and submission instructions are given below for each part. Note that each part has a total of 24 marks allocated for correctness, as               indicated; in addition, 1 mark for each part will be allocated for appropriate coding style                       (commenting, formatting, variable names, etc).

Part 1: Python

You should write the code for each task below in the same python source file, as indicated below. You should then submit your source file through Moodle as described at the end.

Python Task 1a : tkinter GUI and Database

Create a program that should display the following screen [4 marks]:

The programme should save the valid usernames and passwords in a database called Users when the Save button is clicked. [4 marks]

It should clear all the windows when the Clear button is clicked. [2 marks]

If a user clicks the button “Display”, the system should display all usernames and passwords saved in the database. [3 marks]

Python Task 1b: Username and password validation

The system should not save duplicated usernames. If a user enters a username, the system should   check if the username already exists in the database. If the username already exists in the database, the system should display a suitable message. [5 marks]

The password should meet the following criteria:

a)   The password should have a minimum of 8 characters.

b)   The password should include numbers.

If the password does not meet BOTH criteria, the system should reject it with a message saying that it does not meet the requirements. [6 marks]

Python submission

Ensure your submission file is named exactly as it is supposed to (i.e. your_name_python_task.py) Go to your moodle account, and submit your file at the appropriate submission link:

Moodle > Programming and System Design > Lab Exam > Python Submission

Part 2: Java

Your task is to develop classes to model a world involving Citizens and Traders, where Citizens are    able to exchange gems for Goods including bread, wool, armour, weapons, and building materials.    All of those goods are provided by Traders in exchange for gems. Every Trader supports one or more Trades, where a Trade includes the following information:

-     The price in gems

-     The specific goods that are for sale

-      How much of that goods is available for the price

The following is an example of a Trade:

-     Trade 1 gem for 3 Bread

Every Citizen has an amount of gems along with an amount of Goods of each type (which may be zero). When a Citizen successfully executes a Trade, the following happens:

-     The relevant amount of gems is removed

-     The relevant amount of Goods is added

For example, if a Citizen initially has 5 gems and an empty inventory, after executing the above  trade, they would have 4 gems and 3 Bread in their inventory. If a Citizen does not have enough gems to complete a trade, they cannot execute it.

Trades are provided by Traders. When a new Trader is created, they only have one Trade available.   Each time a Trader makes a trade with a Citizen, a new (randomly-chosen) Trade is added to their      set. So if a Trader starts with the sample Trade above, after three successful trades with Citizens, the Trader might have the following Trades in their list:

-     Trade 1 gem for 3 Bread

-     Trade 2 gems for 1 Helmet

-     Trade 1 gem for 1 Bread

-     Trade 2 gems for 4 Wool

(Note that this trader has two Trades for the same item of Goods – Bread. This is not a problem in the system – you do not need to check for duplicates.)

Java Task 1: Goods (3 marks)

Note about implementation: all classes created in this exam should be put in the trading package.

You must create an enumerated type Goods with the following values:

BREAD, COAL, FISH, HELMET, IRON, PAPER, SHIELD, SWORD, WOOD, WOOL

Java Task 2: Trade (7 marks)

You must create a class Trade representing a single trade, including the following properties:

•    gems: the number of gems involved in the trade (an integer)

•    amount: the amount of goods involved in the trade (an integer)

•    goods: the type of goods involved in the trade (an object of type Goods)

For example, the trade “1 gem for 3 BREAD” would be represented as:

-     gems: 1

-      amount: 3

-     goods: Goods.BREAD

The Trade class should have a public constructor that initialises all of the fields, and should also include the following methods:

•    A complete set of get methods, but no set methods

•    Appropriate implementations of equals() and hashCode() – note that equality should be based on the values of all three fields.

•    An implementation of toString() that produces a string representation of the Trade similar to the example above (“1 gem for 3 BREAD”).

Not that you can use automatically-generated code for the get methods and equals()/hashCode(), but you will need to write the toString() method by hand to meet the specification.

Java Task 3: Citizen (6 marks)

Next, create a class Citizen representing a citizen in the game. The internal details of this class are up to you; here is the required behaviour.

The constructor for Citizen should take a single parameter, an integer representing the number of gems, and should create a new Citizen with that many gems and an empty inventory.

Citizen should have the following public methods:

-      public int getGems() – returns the current amount of gems

-      public int getAmount (Goods goods) – returns the current amount of the indicated Goods    type in the inventory. Should return 0 if the Citizen does not have any of the indicate Goods.

-      public boolean executeTrade (Trade trade) – should check whether the given trade is possible (i.e., whether the Citizen has enough gems)

o If the amount of gems is not enough, return false and do not change anything

o Otherwise, update the amount of gems and the inventory based on the details of the Trade and return true