You cannot declare a variable in the interface. Variables, properties and methods can't be declared in the interface.
It is not possible to instantiate an interface in java. The class that implements any interface must implement all of the methods of that interface, otherwise the class should be declared abstract.
Any interface can be extended, but cannot be implemented. If there are two or more same methods in two interface and a class implements both interface, then implementation of the method is enough.
inf2 has to provide the implementation of all the methods of interfaceinf1, because interfaceinf2 extendsinf1.
Can I create object for interface?
You can't instantly create an interface. Most of the methods are incomplete, except for the default and static methods introduced in Java8.
Is it possible to create an object with an interface? It is not possible to say yes. An object is created from the code you have shown.
An interface is nothing more than a contract. By allowing a class to implement an interface, you can make sure that the class follows the contract. At the intermediate language level, IPerson is an abstract class containing virtualmember stubs that only has a signature.
The implementor class will have to use logic in order to get the skeleton to work. There isn't a way to create an instance of the interface because the abstract class doesn't have a constructor.
When a class implements an interface, only the instance side of the class is checked, so you can describe methods in an interface that are implemented in the class. The constructor is not included in this check because it is in the static side.
There is a comparable interface. This interface can be used to sort a collection if the class implements it. The interface should be declared using the interface keyword. It is used to provide a lot of information.
All methods in an interface are declared with an empty body and all fields are public, static and final by default. All methods declared in the interface must be implemented by the class that implements it. Implementation of interface use is carried out with the use of the keyword.
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CAN interface have final variable?
All classes try to access and modify the interface variable when one interface is implemented by many classes. It leads to inconsistent changing of data and affects every other class. The access modifier needs to be declared with the final.
If one of the implementing classes changed the value of the interface, there will be confusion among the other implementing classes. Because interface can't be instantiate, the declaring variable inside the interface will be static and final.
There are similarities between theinterfaces. There is only one interface and all the objects are associated with it. It is not possible for each object that implements the interface to have their own copy of the interface since the interface only exists one time as a Class.
There is only one instance of each variable, that's what it means. The variables are shared by all of the classes that use the interface. The final public static variables are here.
I think interface variable are static because of that. As we can't have objects of interface, we should use class level variables and avoid using object level member variables.
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CAN interface have a constructor?
No, we can't have a definition in an equation. There will be a method in that interface. The implementation of a method in an interface will be provided by the implementing class and the method body will be public.
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Can we have members in interface?
Members other than interface members can be contained in the File Info class. You can only access interface members through the instance of an interface type, when you implement an interface explicitly.
Only the member interface can be privatepertained within a directly enclosing class declaration.