java interface vs abstract class stackoverflow

Java interface vs abstract class stackoverflow for free#
Java interface vs abstract class stackoverflow code#

So the class defines what the class is but the interface tells us things about it. A particular dog breed class, say a YorkshireTerrier, may be a descended of the parent dog class, but it is also implements IFurry, IStubby, and IYippieDog.

I like to think of interfaces as a way to characterize a class. In the best case that base class will save a lot of work. As a general guideline always provide an abstract base class implementation of an interface if for nothing else as an example of a way to implement the interface. That being said there certainly is a place for interfaces. I have not heard of even one case in which somebody regretted that they shipped a class. Many of them, including those who initially disagreed with the guidelines, have said that they regret having shipped some API as an interface. NET Framework, I have talked about this guideline with quite a few developers on our team.

Over the course of the three versions of the. As long you make the right modifications, which includes adding new functionality, you will be able to extend and evolve your code.

Java interface vs abstract class stackoverflow code#

With a class however, you can modify it and not break code that links to it. Once an interface is shipped, you don't get the chance to change it without breaking code that used that interface. NET specific, but the Framework Design Guidelines book argues that in general classes give more flexibility in an evolving framework. Things can be messy if you make a change to the base implementation for one guy and break the others.

Class derivations may come to depend on some base behavior (have intricate knowledge of parent implementation).Base classes normally indicate type hierarchy (IS A).Abstract Base classes can't be mocked easily like interfaces.Base classes can declare protected and public functions that can be accessed by derivations.Derivations do not need to do anything special Changing the base class is relatively easy.Even if could from multiple classes, it is usually a bad idea. Except C++, you can only derive from one class.

Java interface vs abstract class stackoverflow for free#

Allows you to add some default implementation that you get for free by derivation (From C# 8.0 by interface you can have default implementation).Interface implementations are decoupled / isolated from each other.Interfaces normally indicate a kind of behavior.You can use mock frameworks to mock out anything behind an interface Implementations have to implement all members. All implementations need to be recompiled/modified.

Modifying an interface is a breaking change.

Most languages allow you to implement multiple interfaces.

If you add a method to an interface it'll break all of it's implementations. On the other hand, interfaces are very hard to evolve. Interfaces enable safe, powerful functionality enhancements via the Interfaces allow the construction of nonhierarchical type Interfaces are ideal for defining mixins.

Well, Josh Bloch said himself in Effective Java 2d: Prefer interfaces over abstract classesĮxisting classes can be easily retrofitted to implement a new exceptions include C++) but be able to implement multiple interfaces, it allows you to construct objects in a strictly as required basis. Theoretically you can override them from a higher base class, but essentially an interface allows you to add on only the things you need into a class without the need for inheritance.Ĭonsequently, because you can usually only inherit from one abstract class (in most statically typed OO languages that is. Your Dog and Cat definitions should now look like: public class Dog : Mammal, IPettable The implementation for the above contract will not be the same between a cat and dog putting their implementations in an abstract class to inherit will be a bad idea. That's where an interface will be useful: public interface IPettable However, giraffes, rhinoceros, and hippos are not exactly animals that you can make pets out of. This will still be valid because at the core of the functionality Feed() and Mate() will still be the same. Now let's suppose there are other mammals, which we will usually see in a zoo: public class Giraffe : Mammal To define this you will have: public class Dog : Mammal This base class will probably have default methods such as:Īll of which are behavior that have more or less the same implementation between either species. Let us assume that you have an abstract class Mammal, for both of them: public abstract class Mammal Let's take your example of a Dog and a Cat class, and let's illustrate using C#:īoth a dog and a cat are animals, specifically, quadruped mammals (animals are waaay too general).