The difference between interface and abstract class (ii)

Requirement One: Ordinary door

Version 1.0

Abstract class Door {    publicabstractvoid  open ();      Public Abstract void close ();} class extends Door {    @Override    publicvoid  open () {}    @Override      Public void close () {}}

Version 2.0

Abstract Interface Door {    publicabstractvoid  open ();      Public Abstract void close ();} class Implements Door {    publicvoid  open () {}    publicvoid  Close () {}}

Demand two: Alarm door

Version 1.0

Abstract classDoor { Public Abstract voidopen ();  Public Abstract voidClose ();  Public Abstract voidalarm ();}classNormaldoorextendsDoor {@Override Public voidopen () {} @Override Public voidclose () {} @Override Public voidalarm () {}}

Version 2.0

Abstract InterfaceDoor { Public Abstract voidopen ();  Public Abstract voidClose ();  Public Abstract voidalarm ();}classNormaldoorImplementsDoor { Public voidopen () {} Public voidclose () {} Public voidalarm () {}}

Version 3.0

Abstract classDoor { Public Abstract voidopen ();  Public Abstract voidclose ();}Abstract Interfacealarm{ Public Abstract voidalarm ();}classNormaldoorextendsDoorImplementsAlarm {@Override Public voidopen () {} @Override Public voidclose () {} Public voidalarm () {}}

Comments:

Ordinary door, version 1.0 If you add a non-abstract method, the subclass automatically has it and does not need to change the code (advantage)

Alarm door, Version 1.0 all sub-categories, to implement the alarm, but many doors do not need to alarm (disadvantage)

Alarm, version 2.0 because the interface added an alarm function, so that all the use of the interface has to change the code, or the compilation does not pass. Disadvantage

Among the alarms, version 3.0 is the right way to handle

Interface is the abstraction of behavior, ordinary Gate 2.0 and Alarm Gate 2.0 are not appropriate.

Abstract class is an abstraction of an object, so the normal gate 1.0 is appropriate.

The difference between interface and abstract class (ii)