Copy, from the accompanying website, the Book and Library classes and then implement a tester for the Library class. Make the changes to the StockItem class you considered in self-test question 4...

Copy, from the accompanying website, the Book and Library classes and then implement a tester for the Library class. Make the changes to the StockItem class you considered in self-test question 4 above, then: (a) Write a tester that adds five StockItem objects into a set. (b) Modify the tester so that the set is displayed using the toString method of Set. (c) Use the contains method of Set method to search for one of the stock items.