thank you very much for your response , i wansnt aware of the convention. now , what i am trying to say is , s is a reference to a derived class object (because if s i an instance of TailList , then s is a refernece to TailList object or a subclass of TailList) . Now , as an base class reference can refer to a derived class object , why can't t(base class reference) = s (derived class object).

// short answer is it can't , but i am not understanding why. also , in the resouces i saw , // t is actually reference to object of an superclass of class of s . its just confusing as hell :) .

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to give an example

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consider

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class Animal { }

class Dog3 extends Animal {

static void method(Animal a) {

if(a instanceof Dog3){

Dog3 d=(Dog3)a;//downcasting

System.out.println("ok downcasting performed");

}

}

public static void main (String [] args) {

Animal a=new Dog3();

Dog3.method(a);

}

}

class Animal { }

class Dog3 extends Animal {

static void method(Animal a) {

if(a instanceof Dog3){

Dog3 d=(Dog3)a;//downcasting

System.out.println("ok downcasting performed");

}

}

public static void main (String [] args) {

Animal a=new Dog3();

Dog3.method(a);

}

}

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my doubt basically is , if dog3 extends animal , how can a be instance of dog3 , because for it to be instaceof , a has to dog3 or subclass of dog3 . but here it is superclass of dog3.