Whats the difference between subClass sc = new subClass() and superClass sc = new subClass?

Question

class superClass {}

class subClass extends superClass{}

public class test
{

    public static void main()

{

    superClass sc1 = new subClass();
    subClass sc         


        

Answer 1

In both the cases, objects of subClass will be created, but the references will be different.

With the reference of superClass i.e sc1 , you won't be able to invoke the methods present in the subClass but not in the superClass. You will require casting to invoke the subClass methods.

Like :

class superClass {
   public void superClassMethod(){
   }
}

class subClass extends superClass{
   public void subClassMethod(){
   }
}

Now :

public class test
{
  public static void main(){

    superClass sc1 = new subClass();
    subClass sc2 = new subClass();
    //whats the difference between the two objects created using the above code?


    sc2.subClassMethod(); //this is valid

    sc1.subClassMethod(); // this is a compiler error, 
                          // as no method named subClassMethod
                          // is present in the superClass as the
                          // reference is of superClass type

   // for this you require a type cast

   (subClass)sc1.subClassMethod(); // Now this is valid

  }
}