Question

I have two classes: Teacher and Coordinator. Coordinator extends Teacher.

Basically I wanted to make an instance variable that could take in either a Teacher instance or Coordinator instance.

I know this is easily possible by just writing Teacher exp = new Teacher() or Teacher exp = new Coordinator(), however when I do this, I am only able to access Teacher methods and properties when I apply new Coordinator() or new Teacher() to the reference variable which is normal. My question is that is there another way where I only use one instance variable that can be assigned to Teacher OR Coordinator objects and use this variable to call any property/method of the object that was assigned to the object reference variable?

Answer 1

You can check if exp is a Coordinator then cast and call its function accordingly:

if(exp instanceof Coordinator) {
    ((Coordinator)exp).foo();
}

If you have several things you want to do, you can create a variable in a local scope and use it repeatedly:

if(exp instanceof Coordinator) {
    Coordinator expCoord = (Coordinator)exp;
    expCoord.foo();
    expCoord.bar();
    expCoord.baz();
}