Are there any reasons to have an abstract class with every method in the class defined?

Question

It seems that an abstract class means the definition of the class is not complete and hence cannot be instantiated.

And I saw some simple Java code which has an abstract

Answer 1

You might have some classes that don't make sense in the context of your application but they do in the design. A silly example: Abstract class animal, implement born and die. You don't want an "animal". You want a Dog. This way you don't have to repeat the code each class you add. Now you can have Dog, Cat or whatever you want, this would be a good reason, anyway it's hard to find.