Method Overriding:
The method overriding is the
process in which methods are implemented in subclasses with the same name and
type as that of the method present in their superclass.
Note: By method overriding Java implements runtime polymorphism
(“one interface, multiple methods”).
In the below program example
method overriding is implemented.
package blog.inheritance.Super1;
public class X
{
int a;
int b;
X(int a,int b)
{
this.a=a;
this.b=b;
}
void add()
{
System.out.println("am add method in
class X");
System.out.println("addition is "+(a+b));
}
}
package blog.inheritance.Super1;
public class Y extends X
{
int c;
int d;
Y(int a,int b,int c,int d)
{
super(a,b);
this.c=c;
this.d=c;
}
void add() // overridden method from class X
{
super.add();// call to superclass
add method
System.out.println();
System.out.println("am add methos in
class Y");
System.out.println("addition reult
"+(c+d));
}
public static void main(String[] args)
{
Y objY=new Y(20, 30, 40, 50);
objY.add();
}
}
Output:
add method in class X
addition is 50
am add methos in class Y
addition reult 80
Dynamic Method Dispatch:
It
is the mechanism by which a call to an overridden method is resolved at
runtime.
When call is made to an
overridden method, Java determines which version of the overridden method to be
invoked based on the type of the object being referred at the time of call
happens.
package blog.inheritance.Super1;
public class X
{
int a;
int b;
X(int a,int b)
{
this.a=a;
this.b=b;
}
void add()
{
System.out.println("am add method in
class X");
System.out.println("addition is "+(a+b));
}
}
package blog.inheritance.Super1;
public class Y extends X
{
int c;
int d;
Y(int a,int b,int c,int d)
{
super(a,b);
this.c=c;
this.d=c;
}
void add() // overridden method from class X
{
System.out.println("am add methos in
class Y");
System.out.println("addition reult
"+(c+d));
}
public static void main(String[] args)
{
Y objY=new Y(20, 30, 40, 50);
X objX=objY; // reference of object Y is assigned to variable of type
X.
objX.add(); // variable of type X is calling the method add
}
}
Output:
am add methos in class Y
addition reult 80
In the above example program you
can clear see that variable of type X which holds the reference to object Y is
calling the add () method. The version of the add () method that is invoked is
the version present in the class Y. The call to the overridden method is
resolved at the runtime based on the reference present in the variable objX,
which is of type X. The reference in the variable objX is pointing to the
object Y. So in the above example program add() method present in the class Y
is invoked.
