Java程序辅导

Friday 2/11
Announcements:
▪ Homework 1 due Today – submit to Sakai
▪ Lab 1 due Monday, 2/14 – submit to Sakai (instructions on 270 website)
▪ Poll – Have you used ArrayList<>??
▪ Quiz 1 next Friday, 2/18
▪ Summer Internship opportunity with Pacific Northwest National Labs [PLU-CS-group]
Next time
▪ Read Sections 1.4 and 1.5
➢ Difference between Interface, Abstract class, and Concrete class
➢ Casting and instanceof
Today:
▪ Questions on Reading Sections 1.2-1.3 or Homework
▪ UML Diagrams
▪ Superclass, subclass and Inheritance
▪ Overloading, Overriding, and Polymorphism
▪ Eclipse coding if time permits – create a class and subclass from a UML
UML Diagram
▪ Create UML Diagram for an Employee class
➢Data/Attributes/Fields
• id
• name
➢Operations/Methods
• Constructor
• getName, getId
• setName
• toString
Employee UML
▪ Create the Employee class using the Employee 
UML Diagram
UML
Superclass Subclass - Questions
For classes Employee and HourlyEmp
▪ What is the relationship between 
the classes (superclass, subclass) 
and what is inherited? 
▪ What is the main purpose of a 
constructor?
▪ What is significance of # visibility 
▪ What is a no-parameter (default) 
constructor?
▪ What is the relationship between 
superclass and subclass 
constructors?
▪ What is overriding?
▪ What is overloading?
▪ What is polymorphism?
Employee e1 = ??
e1.toString()
Employee Class
▪ What is the header for the 
Employee class?
▪ What is the header for the 
HourlyEmp class?
▪ What is the header for the 
SalariedEmp class?
▪ Suppose we have a class 
EmployeeTestMain with a main 
method. How do we create an 
array or an ArrayList to hold 
any type of employee?
Superclass variables subclass objects
Object o = new ?????
Animal a = new ?????
Cat c = (???????) a;
is-a
has-a
In-class Exercises
▪ Start Eclipse and Create a new Java Project: PracticeEmployee
▪ Create the class Employee
▪ Create the subclass HourlyEmp
▪ Create the subclass SalariedEmp (if time permits)
▪ Create the class EmployeeTestMain with a main method
▪ Create an Employee array or an ArrayList
▪ Add some Employees / HourlyEmp / SalariedEmp to the array