Consider again the StockItem class from the programming exercises of Chap. 8. Here is the UML diagram: (a) Identify the purpose of a toString method and define an appropriate toString method for this...

Consider again the StockItem class from the programming exercises of Chap. 8. Here is the UML diagram: (a) Identify the purpose of a toString method and define an appropriate toString method for this class. (b) Identify the purpose of an equals method and define an appropriate equals method for this class. (c) Identify the purpose of a hashCode method and define an appropriate hashCode method for this class.