Thread: a superclass variable can reference a subclass but here why cant cv access ???

class A {
int i;
}

// Create a subclass by extending class A.
class B extends A {
int i; // this i hides the i in A

B(int a, int b) {
super.i = a; // i in A
i = b; // i in B
}

void show() {
System.out.println("i in superclass: " + super.i);
System.out.println("i in subclass: " + i);
}
}

class UseSuper {
public static void main(String args[]) {
B subOb = new B(1, 2);
A cv;
cv=subOb;
cv.show();


}
}

When posting code, please use the highlight tags. And please post the specific error you're talking about. I had to copy and paste this code just to know what you were asking. Make it easy for people to help you!

The reason that cv can't access the show() method is because show() is only defined for instances of B. Although cv happens to be an instance of B, there's no guarantee that that's the case when you try to call the show() method. You could also have defined cv as an instance of A, or some other class that extends A but doesn't have the show() method.

This example demonstrates the same concept:

class A {
 
	public static void main(String args[]) {
 
		String strString = "test";
		System.out.println(strString.charAt(0));
 
		Object objString = strString;
		System.out.println(objString.charAt(0));
 
	} 
}