Lesson 18 - Abstract class, comparing and operators in Kotlin
In the previous lesson, Type casting and object hierarchy in Kotlin, we learned about type casting and created an object hierarchy with a common ancestor in Kotlin. In today's tutorial, we're going to continue with that project.
Abstract class
An abstract class is a class whose instance doesn't make sense. Mainly
because it's too vague, e.g. our Animal class. The point is to call
on specific Animal descendants, e.g. a dog, so we won't actually
instantiate the Animal class directly ever. In
other words, it's better to prevent any instantiation of the class overall. To
do that, we simply add the abstract modifier before the
Animal class:
abstract class Animal(var weight: Int) { // . . .
The program works the same as before, but if we try to create an instance of
the Animal class, we'll get an error:
// this code won't work animals += Animal(10)
Other than preventing instantiation, abstract classes can do several other things
...End of the preview...
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