Java Polymorphism Part 2

Java/J2ee Programming Training
Polymorphism

Classification: Restricted
Agenda
• Poly- many
• morphism –forms.
• An entity existing in more than one form.
• methods,
• objects.

Polymorphism
• polymorphism
• static polymorphism
• entity exists in more than one form physically
• implemented in java using method overloading concept
• dynamic polymorphism
• type of the object is decided at run time
• implemented using
• method overriding
• polymorphic arguments, return types
• abstract classes
• interfaces.

Polymorphism
• Method overloading
• method physically exists in more than one form.
• method with the same name but different signature list.
• signature of the method should differ atleast
• number of arguments
• data type of arguments
• order of arguments.
• which function to invoke is decided at compile time( early binding )

Static Polymorphism
public void add( int a, int b)
Differs in Number of arguments
public void add( int a , int b)
public void add( int a, int b, int c )
Differs Datatype of arguments
public void add ( int a , int b)
public void add( int a, float b)
Differs in Order of arguments
public void add( float a, int b)

{
System.out.println( “sum = “+(a + b) );
}
public void add( int a, int b, int c)
{
System.out.println( “sum = “+(a + b +c ) );
}
{
}
{
}
public static void main(String args[] ) {
int a = 10; int b = 20;
add( a, b);
}

{
}
{
}
int a = 10; int b = 20; int c = 30
add( a, b, c );
}
number of
argument
s varies

{
}
{
}
{
}
int a = 10; float b = 30.5;
add( a, b);
}
datatype of
arguments varies

{
}
{
}
{
}
float a = 10; int b = 30.5;
add( a, b);
}
order of arguments
varies

Polymorphism
• public void add( int a , int b )
• public int add( int a , int b)
• return type is not taken into consideration
• public void add( int a , int b )
• private int add( int a , int b)
• access specifier is not taken into consideration

DynamicPolymorphism
• Method overriding
• functions have the same signature but different logic
• methods inherited from the base class are overridden in child class.
• access specifier can be more friendly.
• supports late binding principle

public class Employee
{
private String uname,email;
public void register()
{
System.out.println(“Enter uname”);
uname = sc.next();
System.out.println(“Enter email”);
email =sc.next();
}
}
public class Employee2 extends Employee
{
private String biometrics;
{
super.register();
System.out.println(“scan finger”);
biometrics =“finger pattern”;
}
}
Employee
String uname
String email
+ void register()
Employee2
String uname
String email
+ void register()

public class Employee
{
private String uname,email;
{
System.out.println(“Enter uname”);
uname = sc.next();
System.out.println(“Enter email”);
email =sc.next();
}
}
public class Employee2 extends Employee
{
private String captcha;
{
super.register();
System.out.println(“Enter Image”);
captcha=“ABc123”;
}
}
Employee
String uname
String email
+ void register()
Employee2
String uname
String email
+ void register()

Shape
String name;
int dim1;
int dim2;
Rectangle
String name;
int dim1;
int dim2;
+ void details()
+void area();
Triangle
String name;
int dim1;
int dim2;
+void details();
+void area();
+ void details()
{
S.o.p (name +” “ + dim1 + “ “ +dim2 );
}
+void area()
{
S.o.p (“area = “ + dim1 * dim2);
}
+ void details()
{
S.o.p (name +” “ + dim1 + “ “ +dim2 );
}
+void area()
{
S.o.p (“area = “ +0.5f * dim1 * dim2);
}
+ void details()
{
S.o.p (name +” “ + dim1 + “ “ +dim2 );
}
+void area()
{
S.o.p (“area = “ +0.5f * dim1 * dim2);
}
+ void details()
{
S.o.p (name +” “ + dim1 + “ “ +dim2 );
}
+ abstract void area();

Animal
String name;
int height;
int weight;
Cat
String name;
int height;
int weight;
+ void details()
+void makeNoise();
Dog
String name;
int height;
int weight;
+void details();
+void makeNoise();
+ void details()
{
S.o.p (name +” “ + height+ “ “ +weight);
}
+void makeNoise()
{
S.o.p (“cat meow meow“);
}
+ void details()
{
}
+void makeNoise()
{
S.o.p(“Dog’s bow”);
}
+ void details()
{
}
+void makeNoise()
{
S.o.p (“whattype of noise????”);
}
+ void details()
{
}
+ abstract void makeNoise();

Animal
String name;
int height;
int weight;
Cat
String name;
int height;
int weight;
+ void details()
+void area();
Dog
String name;
int height;
int weight;
+void details();
+void area();
+ void details()
{
}
+void makeNoise()
{
S.o.p (“cat meow meow“);
}
+ void details()
{
}
+void makeNoise()
{
}
+ void details()
{
}
+void area()
{
S.o.p (“whattype of noise????”);
}
+ void details()
{
}
+ abstract void makeNoise();
Animal is an abstract
class
Cat is
concrete
Dog is
concrete
Concrete
method
Concrete
method

Abstract
• Animal is an abstract class.
• We can create an object of abstract class.
• Animal animal = new Animal();
• Objects have well defined behavior.
• Object has well defined behavior, makeNoise() method in animal
class doesn’t have behavior.
• jvm doesn’t know about the object behavior and prohibits
creating the object.

Abstract Classes
• Animal animal = new Animal();
What type of
Animal…dog..or
cat…??
do animal make same
type of Noise????
Then let us not
create the object
of Animal…make
Animal class
abstract.

a.makeNoise()
Dog
String name;
int height;
int weight;
String xxx;
+void makeNoise()
{
S.o.p(“Dog’s
bow”);
}
Cat
String name;
int height;
int weight;
String yyy;
+void makeNoise()
{
S.o.p(“cats
meow”);
}
Animal
String name;
int height;
int weight;
+void
makeNoise()Animal a = new Dog();

a.makeNoise()
Dog
String name;
int height;
int weight;
String xxx;
+void makeNoise()
{
S.o.p(“cats meoww”);
}
Cat
String name;
int height;
int weight;
String yyy;
+void makeNoise()
{
}
Animal
String name;
int height;
int weight;
+void makeNoise()Animal a = new Cat();

Dog
String name;
int height;
int weight;
String xxx;
+void makeNoise()
{
S.o.p(“cats meoww”);
}
Cat
String name;
int height;
int weight;
String yyy;
+void makeNoise()
{
}
Animal
String name;
int height;
int weight;
+void makeNoise()
+void playSound( Animal a )
{
a.makeNoise();
}

Dog
String name;
int height;
int weight;
String xxx;
+void makeNoise()
{
S.o.p(“Dog meoww”);
}
Cat
String name;
int height;
int weight;
String yyy;
+void makeNoise()
{
S.o.p(“Cat meow”);
}
Animal
String name;
int height;
int weight;
+void makeNoise()
+void playSound( Animal a )
{
a.makeNoise();
}

Interfaces
• Interfaces – prototype
• all methods declared in an interface are by default abstract
• member variables are static and final

<<Employee>>
public static final int MIN_LEAVE= 1;
public static final int MAX_LEAVE = 30;
abstract void applyLeave();
abstract void cancelLeave();
EmpFileSystem
public String filename;
public int MAX_SIZE;
+ void applyLeave()
{
//code for applyLeave
}
+ void cancelLeave()
{
}
EmpDatabaseSystem
public String dbName;
public String url
+ void applyLeave()
{
//code for applyLeave
}
+ void cancelLeave()
{
}

Thank You

Java Polymorphism Part 2

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Java Polymorphism Part 2