As I can understand here 'a1' reffed to a class B object which has 'a=200' as an attribute. Therefore I expected program will print 200. But why does this program prints 100 instead of 200?
class A{
int a=100;
}
class B extends A{
int a=200;
}
class Demo{
public static void main(String args[]){
A a1=new B();
System.out.println("a : "+a1.a); //Prints 100
}
}
By declaring a field in class B that has the same name as a field in its parent class A, you are essentially hiding that field. However, field access on a variable is done based on that variable's declared/static type.
In other words, fields are not polymorphic entities like methods are.
In this case, the variable a1 is declared as type A. The field accessed will therefore be the one in the parent class, A.
Some declarations may be shadowed in part of their scope by another declaration of the same name, in which case a simple name cannot be used to refer to the declared entity.B it's shadow a ? cause if they are in the same package A.a is in part of the scope or im confused?B.a is hiding the A.a. If you had a static field called c and a static method in the same class that declared a local variable c, that c would shadow the static c.Docs saying
Within a class, a field that has the same name as a field in the superclass hides the superclass's field, even if their types are different. Within the subclass, the field in the superclass cannot be referenced by its simple name. Instead, the field must be accessed through super
So in your case the field a of class B hidden by the super calss A
If you want to get the value,
class Demo{
public static void main(String args[]){
A a1=new B();
System.out.println("a : "+a1.a); //Prints 200
}
}
class A{
int a=100;
}
class B extends A{
public B() {
super.a=200;
}
}
