Can an abstract class have a constructor?

Question

Can an abstract class have a constructor?

If so, how can it be used and for what purposes?

Answer 1

Since an abstract class can have variables of all access modifiers, they have to be initialized to default values, so constructor is necessary. As you instantiate the child class, a constructor of an abstract class is invoked and variables are initialized.

On the contrary, an interface does contain only constant variables means they are already initialized. So interface doesn't need a constructor.