CODEWITHSUNDEEP
java
GuruKulki
GuruKulki

Reputation: 26428

why we should not use static and abstract for a single method?

why we should not use static and abstract for a single method?

Upvotes: 3

Views: 3165

Answers (4)

JonH
JonH

Reputation: 33163

the static keyword is defined so that a method can be called by a class name rather then an object. that means the method has to have some sort of definition. but abstract means you do not have any details about what the method does, it is as it says **Abstract**. When you inherit or extend a class you can then define the method.

Think of an interface.

If you are asking about having a static method inside of an abstract class, that is a different story. An abstract class is essentially as mentioned an interface and contains just a template of say functions that you must later on implement by inheriting / extending the class. Once you extend that class the static method does not come along with it (that is by default unless the access modifier is public / protected).

Upvotes: 7

TofuBeer
TofuBeer

Reputation: 61536

The abstract keyword means that child classes must override the method - this is (one of the ways) Java supports polymorphism. If you want to make it so that subclasses cannot override the method you mark it final. So it would be impossible to have an "abstract final" method since they are the exact opposite of each other.

the static keyword implies final as well - all static method are also final. Thus it is impossible to have a method that is both static and abstract since you would be able to make a method that is abstract and final.

The reason for static being final is that it is bound to the class instead of the instance. That means that the compiler looks it up at compile time rather than runtime to determine which method to call. The reason what it is like that? Arbitrary decision that the designers of Java made - they could have allowed static method to be overridden but decided not to. I don't have any particular insight as to why the chose one over the other unfortunately.

Upvotes: 5

Drew Wills
Drew Wills

Reputation: 8446

As others have said, static+abstract is nonsense in Java. But there have been (rare) occasions where I've wished I could do just that.

The result I was looking for was basically to say that... "all concrete classes that extent this abstract class (or implement this interface) must provide a static method with this signature." This capability would allow these classes to provide meta-information about themselves.

Normally I have ended up with an instance method in these cases. If you stipulate that concrete implementations must support the default (no-arg) constructior, you can do...

MyInterface obj = MyClassThatImplementsMyInterface.newInstance();
obj.invokeTheMethodIWishWasBothStaticAndAbstract();

Upvotes: 0

KLE
KLE

Reputation: 24169

A static method is not inherited. Therefore, making it abstract is a nonsense.

Upvotes: 5

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