Question

I’m a beginner in Java programming and would like to understand what is the right way for working with polymorphic references here.

Suppose we have the following (abstract) code in C++:

List<Fruit*> lstFruit;
...
// collect apples here
while (...)
{
  Fruit* apple = new Apple("green");
  lstFruits.append(apple);
}
...
lstFruit[i]->doSomething(); // here is our virtual method

Java doesn’t let me create a List collection with references to a base class that is abstract. What should I do in this situation? My goal is to work with different objects of child classes universally, no matter what their class actually is.

Answer 1

You can create a generic collection with astract class:

List<Fruit> l = new ArrayList<Fruit>();
l.add(new Apple());
l.get(0).someFunctionOnFruit();