1. CS240: Advanced Programming Concepts
Week 5
Thursday

2. Inheritance Continued…
Scope
Private
“Mine”
Cannot be seen/accessed by any other class – including subclasses
Use public/protected methods to access…
Protected
Visible within the package…
Visible to subclasses outside of the package – but only for instances of the subclass type
Public
“Everyone’s”

3. Interface Variables
Interfaces CAN have variables but they must/will be public, static, and final
Note: this is implicit – it happens without you invoking the keywords…

4. Abstract Methods In interfaces… In Classes
This is basically our default practice…
In Classes
If a method is declared but not defined (i.e. no {}) then it is treated as abstract.
If one or more methods in a class are abstract the class itself must be declared abstract
public abstract class <ClassName> …

5. Static / Default Methods in Interfaces
Static methods
Not originally included in the language – considered a violation of the interface paradigm
Now OK
Enables “Interface Evolution” – discuss…
Default methods
Provided as a means of “offering” a default method to implementing classes
Also Enables graceful “Interface Evolution”
Makes it possible to add methods to an interface without breaking compilation of older code
Prevents runtime errors when running previously compiled older code

6. Method Conflicts
When a class implements two interfaces that have a method naming conflict the implementer must de-conflict the methods (i.e. by implementing the method and calling one of the interfaces’ version)
If a naming conflict arises when a class implements an interface and extends a superclass the superclass is dominant…

7. Static Factory Methods…
Factory methods “manufacture” objects of a particular class
Can be static methods – no need for an instance to call them ( i.e. getInstance() )
Discuss
Sometimes you don’t want your constructor to be public…
Utility Class
Singleton

8. Project 1: Super Asteroids
Deliverables:
Design Document: October 11th (6% of your total grade)
Working Program: October 27th (24% of your total grade)
Code Evaluation: October 27th (6% of your total grade)