Java interfaces are meant to specify fields and methods that are publicly available in classes that implement the interfaces. Therefore you cannot use the private and protected access modifiers in interfaces.
Can we use access modifiers in interface?
You cannot apply access modifiers to interface members. All the members are public by default. If you use an access modifier in an interface, then the C# compiler will give a compile-time error “The modifier ‘public/private/protected’ is not valid for this item.”.
CAN interface have private and protected methods?
2 Answers. Protected methods are intended for sharing implementation with subclasses. Interfaces have nothing to offer as far as implementation sharing goes, because they have no implementation at all. Therefore all methods on interfaces must be public.
Can protected be used in interface?
Because interfaces define public APIs. Anything that’s protected is an internal detail which does not belong in an interface. You can use abstract classes with protected abstract methods, but interfaces are restricted to public methods and public static final fields.
What is interface example?
An interface is a description of the actions that an object can do… for example when you flip a light switch, the light goes on, you don’t care how, just that it does. In Object Oriented Programming, an Interface is a description of all functions that an object must have in order to be an “X”.
Can we put a static method in interface?
Similar to Default Method in Interface, the static method in an interface can be defined in the interface, but cannot be overridden in Implementation Classes. To use a static method, Interface name should be instantiated with it, as it is a part of the Interface only.
Can an interface be final?
Making an interface final.
If you make a method final you cannot override it and, if you make a variable final you cannot modify it. … If you make an interface final, you cannot implement its methods which defies the very purpose of the interfaces. Therefore, you cannot make an interface final in Java.
Why is private not used in interfaces?
Private members don’t make sense in interface. Interface is a way to access a class with defined methods where you don’t need to see the inners of that class. Private members disagree to that. Members of a class that are declared private are not inherited by subclasses of that class.
Can we declare private variable in interface?
3 Answers. as you have declare variable in test interface with private and protected it will give error. if you do not specify the modifier the compiler will add public static final automatically. Having private or protected members in an interface doesn’t make sense conceptually.
Can we define method in interface?
Like a class, an interface can have methods and variables, but the methods declared in an interface are by default abstract (only method signature, no body). Interfaces specify what a class must do and not how. It is the blueprint of the class.
Can an interface contain a constructor?
Constructor in an interface
An Interface in Java doesn’t have a constructor because all data members in interfaces are public static final by default, they are constants (assign the values at the time of declaration).