1. Inheritance & Polymorphism

2. Specialization & Generalization
The is-a relationship
The dog is a mammal
The cat is a mammal
Dog and cat specialize mammal
Mammal generalize dog and cat
To extract the common parts
In C#, the specialization relationship is typically implemented using inheritance.

3. Example Inheritance_demo Use : for inheritance Access modifiers
Private, protected, public
Override inherited methods
new vs virtual-override
Overload vs overwrite
Observe the which method is called

4. Exercise 13
Please develop a Dog and a Cat class derives from mammal class and specialize them respectively
The mammal class is given as the next slide

5. class Mammal {
protected string speciesName = "Mammal";
public Mammal(string speciesName)
this.speciesName = speciesName; }
public void Sound()
Console.WriteLine("The sound of {0} => hmm...hmm...", speciesName);

6. The root of all classes - Object
Every thing is an object of Object in C# !!

7. Example (5-4)
bad naming

8. Exercise 14
What will the message be if you don’t override the toString() in example 5-4?
To understand why and when we need to do this.

9. Polymorphism The way you look at things Dog aDog = new Dog();
A dog is just a dog
A dog is a mammal
That dog is a hound
Dog aDog = new Dog();
Mammal aMammal = (Mammal) aDog;
ex13

10. Boxing & Un-Boxing
The conversion between value types and reference types
stack vs heap
Boxing is implicit
Un-Boxing is explicit

11. Boxing & Un-Boxing (5-5)
implicit
explicit

12. Interfaces
An interface is a contract that guarantees to a client how a class will behave
Doing nothing but putting a constraint on the implementing class
Ex:

13. Example 8-1
Constructor
Methods
Property

14. Arrays
An array is an indexed collection of objects, all of the same type
Phone book (exercise 10)
myFriend1, myFriend2, … , myFriend100 ?
Expression :

15. Example (ArrayDemo) The phone book exercise can be improved further
Array size
static void Main(string[] args) {
PersonalData[] myFriends = new PersonalData[2];
myFriends[0] = new PersonalData();
myFriends[0].Name = "Mandy Tsai";
myFriends[0].Phone = " ";
myFriends[0].display();
PersonalData.Counter++;
myFriends[1] = new PersonalData("Claire"," ");
myFriends[1].display(); }
Array indexer

16. Exercise 15
Please try to declare and initialize an integer array from 0 to 100
myArray[0] = 0;
myArray[1] = 1; …
myArray[100] = 100;
and prints them out …

17. Some useful stuff Length property System.Array.Sort()
myArray.Lngth
System.Array.Sort()
System.Array.Sort(myArray,0,101);
System.Array.Reverse()
System.Array.Reverse(myArray,0,101);
The foreach loop
foreach(int i in myArray)

18. Multi-dimensional array & ArrayList
You can cast a multi-dimensional array simply by
int[,] myArray = new int[6,8];
ArrayList is used to provide you an array with dynamic size
Using System.Collections;
Add(), Insert()
Remove(), RemoveAt()
Count (property)

19. Example (ex15_modified_2)
ArrayList myArray = new ArrayList();
for(int i = 0; i < 101; i++)
myArray.Add(i); {
if(i != 0 && i%10 == 0)
Console.WriteLine();
Console.Write(myArray[i]+"\t"); }
Console.WriteLine("\n\n");
It is not necessary to provide the size of your array
Add values into our array