super keyword
super is a keyword that refers to the object of super class. Generally, we write sub class variables, constructors and methods in a class. Whenever data members of a class and formal parameters of a method or constructor is existing with same name then system will get confused to overcome this problem “super.” can be useful.
super class variables
class Test1 
{ 
int a=10; 
int b=20; 
}; 
class Test extends Test1 
{ 
int a=100; 
int b=200; 
void add(int a,int b) 
{ 
System.out.println(a+b); 
System.out.println(this.a+this.b); 
System.out.println(super.a+super.b);
} 
public static void main(String[] args) 
{ 
Test t=new Test(); 
t.add(1000,2000); 
} 
};
Output :
output:300,,3000,,30
Super class methods
class Parent 
{ 
void m1() 
{ 
System.out.println("parent class method"); 
} 
}; 
class Child extends Parent 
{ 
void m1() 
 { 
System.out.println("hi"); 
 } 
void m2() 
{ 
this.m1(); 
System.out.println("hello"); 
super.m1(); 
} 
public static void main(String[] arhs) 
{ 
Child c=new Child(); 
c.m2(); 
} 
};
Output :
output:hi,,hello,,parent class method
Super class constructors
class Test1 
{ 
Test1(int i,int j) 
{ 
System.out.println(i+j); 
} 
}; 
class Test extends Test1 
{ 
Test(int i) 
{ 
super(100,200); 
System.out.println(i); 
} 
public static void main(String[] args) 
{ 
Test t=new Test(10); 
} 
}
Output :
output:300,,10
Note :-
   inside the constructors it is possible to call only one constructor at a time that calling must be first statement of the constructor.