Question: Can An Interface Have A Constructor?

Can we override default method of interface?

If you have default method in an interface, it is not mandatory to override (provide body) it in the classes that are already implementing this interface.

In short, you can access the default methods of an interface using the objects of the implementing classes..

Can we have static methods 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 have a constructor C#?

An interface does not have a constructor so one can only create an object of an interface as a subtype. Use of interfaces as instance variables have to be as a subtype of the classes implementing the interface.

Which one is true for an interface?

An interface cannot have instance variables is true about interfaces. Explanation: An interface is similar to a class, but the main difference is that it can have only declaration and the implementation of the functions and procedures will be given by the class which is implementing the interface.

Can a constructor be final?

No, a constructor can’t be made final. A final method cannot be overridden by any subclasses. … In other words, constructors cannot be inherited in Java therefore, there is no need to write final before constructors.

Why are constructors not part of the interface?

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). There are no data members in an interface to initialize them through the constructor.

What happens when a constructor is defined for an interface?

What happens when a constructor is defined for an interface? Explanation: Constructor is not provided by interface as objects cannot be instantiated. 9. What happens when we access the same variable defined in two interfaces implemented by the same class?

What are the advantages of interface?

1) through interfaces we can implement multiple inheritance in java. 2) Interfaces function to break up the complex designs and clear the dependencies between objects. 3) Interfaces makes your application loosely coupled.

Can we create instance of an interface?

No, you cannot instantiate an interface. Generally, it contains abstract methods (except default and static methods introduced in Java8), which are incomplete. Still if you try to instantiate an interface, a compile time error will be generated saying “MyInterface is abstract; cannot be instantiated”.

CAN interface have main method?

Answer : Yes, we can provide different implementation of main() declared in an interface and classes implementing that interface by overriding method and can overload static main method if defined in an interface. Some more information regarding interface changes in Java 8.

When would you use an interface?

Use interface when you want to exactly implement all the abstract methods to the class implementaing the interface and no default body to a method can be provided. It is considered good style to store a reference to a HashSet or TreeSet in a variable of type Set.

Can abstract class have constructor?

Yes! Abstract classes can have constructors! Yes, when we define a class to be an Abstract Class it cannot be instantiated but that does not mean an Abstract class cannot have a constructor. Each abstract class must have a concrete subclass which will implement the abstract methods of that abstract class.

Why interface variables are static and final?

Interface variables are static because java interfaces cannot be instantiated on their own. The value of the variable must be assigned in a static context in which no instance exists. The final modifier ensures the value assigned to the interface variable is a true constant that cannot be re-assigned.

What can an interface contain?

Interfaces can contain instance methods, properties, events, indexers, or any combination of those four member types. Interfaces may contain static constructors, fields, constants, or operators.

Can main method be final?

Yes, we can declare the main () method as final in Java. The compiler does not throw any error. … The main use of the final method in Java is they are not overridden. We can not override final methods in subclasses.

Can we declare an interface as final?

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. Still if you try to do so, a compile time exception is generated saying “illegal combination of modifiers − interface and final”.

Why can’t we instantiate an interface?

You can’t instantiate an interface or an abstract class because it would defy the object oriented model. Interfaces represent contracts – the promise that the implementer of an interface will be able to do all these things, fulfill the contract.

How do we declare an interface class?

An interface is declared by using the interface keyword. It provides total abstraction; means all the methods in an interface are declared with the empty body, and all the fields are public, static and final by default. A class that implements an interface must implement all the methods declared in the interface.