Inheritance

First, consider the following class:
public class State{ private String name,capital; private double populationInMillions; public State( String stName, String stCap, double popMil ){ name = stName; capital = stCap; populationInMillions = popMil; } public String getCap(){ return capital; } public String getName(){ return name; } public double getPop(){ return populationInMillions; } public String toString(){ // SWEET NEW METHOD! return capital + ", " + name + " : " + populationInMillions + " million"; } }
tias.java (quick review 1D array & constructors)
What are our options if we want to include more info with state objects such as two letter postal abbreviation and more?

Approach Pro's Con's
parallel arrays "backward compatible"
(ie, doesn't break other clients) A very good thing! responsibility for keeping indices "matched up"
get source code for State.java & modify to add new instance variables (& methods to access) we know how to do it
NOT backward compatible
(Serious bummer!)
Might not have access to source
It might be handy if our Fish had a method to center itself on a coordinate location.
finny.moveCenterTo( 50, 150 );

cut-n-paste a new class with additional instance variables & methods
we know how to do it
backward compatible yea!
Tedious and repetitive
If good stuff gets added to other class; we'll have to keep copying
OR..... use INHERITANCE
backward compatible yea!
Another learning opportunity!
Insight into how all the libraries are built!
Syntax to learn and keep straight
public class USA extends State{ protected String abbr; public USA( String _name, double _pop, String _cap, String _abbr){ super( _name, _cap, _pop ); abbr = _abbr; } public String getAbbr() { return abbr; } // What about our beautiful new toString() method??? // want to OVER RIDE the toString method of my superclass public String toString(){ String result = super.toString(); result = result + " (" + abbr + ")" ; return result; } }
More Notes

Approach	Pro's	Con's
parallel arrays	"backward compatible" (ie, doesn't break other clients) A very good thing!	responsibility for keeping indices "matched up"
get source code for `State.java` & modify to add new instance variables (& methods to access)	we know how to do it	NOT backward compatible (Serious bummer!) Might not have access to source It might be handy if our Fish had a method to center itself on a coordinate location. finny.moveCenterTo( 50, 150 );
cut-n-paste a new class with additional instance variables & methods	we know how to do it backward compatible *yea!*	Tedious and repetitive If good stuff gets added to other class; we'll have to keep copying
OR..... use INHERITANCE	backward compatible *yea!* Another learning opportunity! Insight into how all the libraries are built!	Syntax to learn and keep straight