.Open CS320/15 OOP and Java
.Table
.Row Prev 14	Data  Abstraction       Chapter 2  section 14 +  Chapter 11     lab14 C/C++ ADTs
.Row **	Project Deadline Phase 2        Phase 2 due in: changed EBNF and draft UML (10pts)
.Row 15	OO  Programming and Java        Chapter 2 section 17 +  Java  Handout +  Chapter 12	lab15 Java101
.Row Next 16	Concurrency and Java    Chapter 13  not sect'n 9        lab16 Java102
.Close.Table
.Open Preparation
 Study Chapter 2 section 17 on Java
  Study the Java Handout.
 Study the $Notes below.
 Study chapter 12 (not section 12) on OOP
 Check out my notes on Java
.See http://cse.csusb.edu/dick/samples/java.html
 Do the review Questions at the end of chapter 12
but don't do any questions on SmallTalk :-(.
 Hand in answers to 2 or more review questions.
.Close
.Open Notes
. Current Lab Examples Trigger Security Warnings -- Ignore
I have 98 Java files prepared over the years for this class .. and most or them
were compiled using an older, less secure Java compiler.  So your browser may
display a security warning.  I think the code is safe for your browser to download and
run.  You can, therefore, tell it to access them.  You can probably tell it to accept any
applet from my web site quite safely.

The problem may be that I have no easy and simple way of `signing` and applet with a
`certification` from a trusted authority.

. Object oriented designs are about messages
Objects compute things by sending messages.  Every message is like a function
call and goes from one object to another.  As a result you can draw a diagram
of an OO program that shows the sequence of calls to and from some objects.

Here is an example of part of a program that simulates a DiceGame that has
two Dice and throws them, and reads their values to work out a score:

.Image OODiceGame.gif [DiceGame creates Dice, Plays game by throwing and read their facevalues]

The code is in 
.See ./java/DiceGame.java
and
.See ./java/Die.java
, enjoy!

. There are No abstract objects -- just abstract classes
        All objects are constructed as an instance of a concrete class. 
        An animal is an abstraction... but each cat and dog
is a concrete example of an animal.
You point at a cat and a dog with the same finger... and
always be pointing at an animal.
        You can have variables that are declared to point at abstraction..... 
                      but can not construct abstract objects.
        You can have variables that are declared to point at abstraction..... 
                      and point them at concrete objects derived from the abstraction.

.Image 16/ole3.gif Abstract vs Concrete

Try out this program:
.See ./15.cpp

. Objects know how to do things -- Polymorphism
      Cats and dogs behave the same even if we change their names.
      Call a cat an animal.... and it still behaves like a cat.

. An object behaves the same however we refer to it. 
      In a non-object-oriented language the behavior depends on its
name.
      In an object-oriented language the behavior is determined by the
object.

.Open An example
       Base class Person and two extended classes Student and
Faculty.
       Each class defines an output function that displays the name of
the Person. 
      Students also display their GPA. 
      Faculty display their rank. 
.As_is       Person * pointer;
.As_is       Faculty dick;
.As_is       pointer = & dick;  
.As_is              pointer->output(); // name and rank
.As_is       Student jo;
.As_is       pointer = &jo; 
.As_is              pointer->output(); // name and GPA
.As_is       pointer = new Student(...); 
.As_is              pointer->output(); // name and GPA
.Close

. Polymorphism in C++
C++ is a hybrid language.  Polymorphism is an option.

The default is to cast objects.  In other words to change the
type of an object to a more abstract type.
This can result in programs that have bugs. 

If an object is assigned to another object of a more general (base) type,
the specific data is stripped away.
It behaves according to the general rules.

This happens with pass-by-value!

So in C++ always
.Set
 Use pass by reference and pass by constant reference
 Do not use rather pass by value. 
 Declare member functions to be virtual.
 Refer to objects via pointers.
.Close.Set
. Full Object-Orientation
Fully object-oriented languages (Java, SmallTalk, etc.) use late (dynamic)
binding by default and these errors are avoided. The cost is that the program
runs slower.
.Close Notes
. Class Work
.See http://www/dick/cs320/15q.html
. Lab Work
.See ./lab/15.html
. Next
.See ./16.html