1. CS-434: Object-Oriented Programming Using Java Week 2
Dr. Jesús Borrego
Adjunct Faculty
Regis University

2. Class Outline Review of Homework 1 and 2 Key Terms
Inheritance, overloading, visibility polymorphism, constructors
Classes, Interfaces, Packages
Sample Program – in class
Homework 3 - Individual
Questions?

3. Review of Homework 1 Create a use case diagram for a library
Include actors, use cases, and relations between users and use cases
Prefer use of Visio
More details in WorldClass (Case Study_Library Application)

4. Review of Homework 2 Create a Hello World program using NetBeans
Capture screen where it shows the package and results
Submit to WorldClass before week 2

5. Key Terms Constructor - Constructor Inheritance - Herencia
Interface – Interfaz
Overloading – Sobrecargar
Package – Paquete
Polymorphism - Polimorfismo

6. Packages A package is a container for classes and other code artifacts
A package contains functionally related items
A package is a namespace
Collection of uniquely defined terms
A main Java API package is called “java”
It is empty but it is used to aggregate other packages

7. Package java java.applet java.awt java.beans java.io Example:
java.util.concurrent.locks
Package java has nested package java.util  that has a java.util.concurrent  that one has java.util.concurrent.locks

8. Visibility
Data types and classes contained in a package are visible to all items in the package
Data types and classes contained in other packages are not visible to others
To access items in other packages, we have to import them:
packageb.ClassB b = new packageb.ClassB();
To avoid this, import the package
import packageb.ClassB;

9. Resolving Ambiguity
If a class appears in two or more packages and we import them, the compiler does not know which one to access
import packageX;
import packageY;
We want class A, but which one?
package1.ClassA aaa = new packageX.classA();
Resolve ambiguity by using Fully Qualified Names (FQN)
packageX
classA
packageY
classA

10. Access Modifiers - Public
Can be applied to class or data members and methods within a class to denote the access is given across package boundaries
package domain;
public class Book {
public void checkOut() {…} … }

11. Access Modifiers - Default
Default – no modifier: Can be applied to class or data members and methods within a class to denote the access is NOT given across package boundaries
Only accessible in the package in which they are defined
package domain;
class Book {
public void checkOut() {…} … }

12. Access Modifiers - Private
Can be applied to data members and methods (but not to classes) within a class to denote the access is restricted to members of the same class
Only accessible in the package in which they are defined
package domain;
public class Book {
private String isbn;
public void getIsbn() {
return isbn; } …

13. Access Modifiers - Protected
Can be applied to data members and methods (but not to classes) within a class to denote the access is restricted to members of the same class and derived classes
package domain;
public class LibraryItem{
protected void setHashCode () {…}
… }
public class Book extends LibraryItem{
public LibraryItem() { …
setHashCode(); }

14. Method Overloading Sometimes we want to use the same name for a method
To differentiate, the methods must have at least one of:
Different number of parameters
Type of parameters
Order of parameters
Return type is a differentiator, so it cannot be used to overload methods

15. Static Fields and Methods
Data members and methods are instance members and therefore ‘non-static’
They are created every time a class is instantiated
Sometimes it is desirable not to instantiate data members (such as constants)
In this case, we use ‘static’
public static final double PI =

16. Inheritance
A class extends another class and acquires properties and behavior of class being extended

17. Inheritance
A class extends another class and acquires properties and behavior of class being extended
package domain;
public class Book extends LibraryItem {
// properties and behavior of Book go here }
public class Audio extends LibraryItem {
// properties and behavior of Audio go here
public class Periodical extends LibraryItem {
// properties and behavior of Periodical go here

18. Class Constructors
A constructor is a method that gets invoked when a class is created
The constructors must have the same name as the enclosing class, and are declared with no return value
Constructors can be overloaded by providing different argument profiles
The constructor with no arguments is the default constructor

19. Default Constructor Characteristics
If no constructor is provided, Java provides a default
If you define at least one constructor, Java does not provide the default
Constructors are useful to initialize newly created object’s data members
Using default parameters, or arguments in the constructor call
Can call other constructors of the same or base class

20. Overriding Methods
Overriding occurs when a method in a base class is redefined in a derived class
To override a method, the signature of both must match identically

21. Abstract Classes
An abstract class is never intended to be instantiated as an object
It is intended to be a base class that provides methods and together form an API
Classes that inherit the abstract class can override its base behavior and these can also be instantiated as objects
These are called templates

22. Inner classes and Anonymous classes
Every Java class should be defined as a public class, in its own file, where the file matches the name of the class, and has a suffix .java
Java also supports Inner Classes
Anonymous classes are also inner classes defined within the context of another class, but do not have a name

23. Inner classes

24. Activity 1 – YouTube Videos
Live Chat 3
Activity 1 – YouTube Videos
YouTube contains videos on creating applications and test cases
Some examples:

25. Activity 2 – Java Program
Demonstrate input and output
Demonstrate use of array manipulation
Demonstrate use of loops
Demonstrate use of random numbers
Create a class file
Create a main that invokes the class

26. Program details The program reads values into an array
It will find the longest word in the array
Demonstrates passing of parameters
Displays the longest word

27. Homework 3
This individual task is to be performed on the Library application
Create and test (using JUnit) a Book class for the Library application project
In addition to properties of author and isbn, with setters/getters, the Book should override Object’s base method “boolean equals(Object)” and have a “boolean validate()” method
Zip up your NetBeans project, and submit to WorldClass before Week 3

28. JUnit Tutorial
Working with JUnit in NetBeans tutorial: T0Z6Zs
Many more in both English and Spanish

29. Questions?