Multiton and observer design patterns_week 3 solution

This exercise will test your knowledge of the multiton and observer design patterns. You will also learn about regular expressions. SET-UP Import the Netbeans project folder named 'AJP-P3-2012-2013-STUDENT'. Open it up. You have been given a set of unit tests. Initially, there will be LOTS of syntax errors in these unit tests. This is expected. The errors will disappear as you write the required classes.
INSTRUCTIONS FOR BRONZE TASK In the src folder of your new project, in the package named uk.ac.tees.bronze.username create a file called Share.java. This class represents one stock market share in a company. Your class should satisfy the following criteria. • The Share class should have a price instance variable that records the price of the share on the stock market in pounds and pence. There should be a setter (mutator) and getter (accessor) method for this instance variable. • Your class will be an implementation of the multiton design pattern. This means that there will only ever be one unique Share instance per named key. • Instances of the class should be kept in a map. • The key to the map will be the unique three letter name of the company e.g. BBC, AXA. This name is always capitalised. • A call to the static method Share.getInstance() that passes a three letter string, all capitals, should succeed i.e. the getInstance() method will return a Share object. • A call to the static method Share.getInstance() that passes an empty string should fail i.e. the getInstance() method will return null. • A call to the static method Share.getInstance() that passes a null should fail i.e. the getInstance() method will return null. • A call to the static method Share.getInstance() that passes a string containing something other than a three latter string, all capitals, should fail i.e. the method will return null. • If the getInstance() method is called for a company that is not currently in the map, create a new Share object with a default value of 1.00 and add it to the map. • If the getInstance() method is called for a company that is already in the map, return the pre-existing Share object. The unit tests I have provided will guide your solution. You will probably need to use regular expressions when checking the validity of the company name. Read about them here: http://docs.oracle.com/javase/tutorial/essential/regex/ Make sure that your solution to the BRONZE task does not have any CheckStyle errors. You cannot pass this task if your code contains CheckStyle errors.
INSTRUCTIONS FOR SILVER TASK In the src folder of your new project, in the package named uk.ac.tees.silver.username create a file called Share.java. This class represents one stock market share in company X. Your class should satisfy the following criteria. • The Share class should have a price instance variable that records the price of the share in company X in pounds and pence. There should be a setter (mutator) and getter (accessor) method for this instance variable. The default value for this variable is 1.00. • Your Share class will be part of an implementation of the observer design pattern. • The state of a Share object (i.e. it's price) is watched by other objects who implement the ShareWatcher interface. When the unit price of this share changes, these watchers should be informed. The Share class should maintain a list of all ShareWatcher objects who have registered as interested. There should be two methods for list management – addShareWatcher(ShareWacther sw) and removeShareWatcher(ShareWatcher sw). • The ShareWatcher interface defines one method – updatePrice(double price). • There are two concrete implementations of the ShareWatcher interface – StockBroker and BankManager. You must write these classes. Both concrete implementations should have an instance variable called portfolio, which records the number of shares currently owned. This instance variable should have an accessor method. • When the updatePrice() method is called in a StockBroker object, that object must make purchase decisions. A StockBroker object will buy shares when the price drops below 2.00. A stock broker will sell shares when the price rises above 3.00. A stock broker buys shares in blocks of 500. These values are passed to the constructor of the StockBroker object. When buying/selling shares, the instance variable of this object should be updated. • When the updatePrice() method is called in a BankManager object, that object must make purchase decisions. A BankManager object will buy shares when the price drops below 1.00. A stock broker will sell shares when the price rises above 4.00. A stock broker buys shares in blocks of 100. These values are passed to the constructor of the BankManager object. When buying/selling shares, the instance variable of this object should be updated. The unit tests I have provided will guide your solution. Make sure that your solution to the SILVER task does not have any CheckStyle errors.
INSTRUCTIONS FOR GOLD TASK In the src folder of your new project, in the package named uk.ac.tees.gold.username, change your solution to the SILVER task so that • Fields and methods that are shared by BankManager and StockBroker are moved into ShareWatcher, which changes from an interface to an abstract class. • In the ShareWatcher class, declare a new instance variable called balance, which records the current financial status of the ShareWatcher object. To calculate the balance variable, simple calculate: Total expenditure on shares – total income from selling shares For example, if I bought 100 shares at 1.20, and sold them at 3.10, my balance should be 190.00. Note that a balance can be a minus figure. • Modify the BankManager class so that a BankManager object never exceeds a balance of -500.00 • Modify the StockBroker class so that a StockBroker object never has a portfolio of more than 3000 shares. The unit tests I have provided will guide your solution. Make sure that your solution to the GOLD task does not have any CheckStyle errors.