What is the difference between this() and super()?
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Answer Posted / b.h srinath
This is a keyword that refers to the present/current class.
Usage of this:
1)it can be used to invoke constructor
syntax:this();
example: public sample
{
this(20);
this.display();
}
It is mandatory that,when we are calling constructor through
'this' it must be first statement in that method or constructor.
2)It is used to access data members
example:
this.len=len;
this bth=bth;
3)It is used to access member methods
example:
this.getvalue();
this.setvalue();
super() keyword:
super is a keyword that refers to super class from a subclass.
That means super can refer to super class
i)super class instance variable
example:System.out.println(super.a);
program: class A
{
int a = 30;
}
class B extends B
{
void show()
{
int a=10;
System.out.println("The a Value in super
class is"+super.a);
System.out.println("The a Value in super
class is"+a);
}
public static void main(String[] args)
{
B b=new B();
b.show()
}
}
ii)super class methods
example:super.setvalue();
program:
class one
{
int x,y,s;
one()
{
System.out.println("First went to one default const of super
class");
}
void show(int a,int b)
{
x=a;
y=b;
System.out.println("\n superclass value X is"+x);
System.out.println("\n superclass value Y is"+y);
}
void gets()
{
s=x+y;
}
}
class two extends one
{
int a,b,c;
two()
{
System.out.println("\n second came to default const of
child class");
}
void show()
{
super.gets();
System.out.println("\n baseclass value is"+s);
}
}
class intmet
{
public static void main(String args[])
{
two t=new two();
t.show(2,3);
t.show();
}
}
iii)super class constructor
example:super(a);
super(a,b) and so on
program:
class one
{
int x;
one()
{
System.out.println("First went to one default const of super
class");
}
one(int x)
{
System.out.println("\nas the supre(a)is referd one parameter
const is printed");
this.x=x;
}
void show()
{
System.out.println("\none parameter const value is"+x);
}
}
class two extends one
{
int x,a;
two()
{
System.out.println("\n second came to default const of
child class");
}
two( int a,int b)
{
super(a);
System.out.println("\ntwo const");
x=b;
}
void show()
{
System.out.println("\ntwo parameter const value is"+x);
super.show();
}
}
class const1
{
public static void main(String args[])
{
two t=new two();
two t1=new two(2,3);
t1.show();
}
}
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