Establish a basic form for all the derived classes. To express only the interface, and not a particular implementation.
| position | ease | box | interval | due |
|---|---|---|---|---|
| front | 2.5 | 0 | 0 | 2021-01-23T15:52:20Z |
Classes have abstract methods (or not).
abstract class Basic {
abstract void f();
}
Derived classes of abstract classes must implemente abstract methods. If not, the derived class is still abstract class.
abstract class Base2 extends Basic {
int f() { return 111; }
abstract void g();
// f still not implemented
}
Allow almost all Java Access Control modifiers, except private abstract (no sense for it);
whereas Java Interface only allow public methods.