Question: Can We Have Method Body In Interface?

Why Interface members 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..

CAN interface have a constructor?

No, you cannot have a constructor within an interface in Java. You can have only public, static, final variables and, public, abstract, methods as of Java7. From Java8 onwards interfaces allow default methods and static methods.

Can an interface be 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”.

Do you have to override interface methods?

The default methods are introduced in an interface since Java8. Unlike other abstract methods these are the methods can have a default implementation. 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.

CAN interface have methods?

Interfaces are declared using the interface keyword, and may only contain method signature and constant declarations (variable declarations that are declared to be both static and final ). All methods of an Interface do not contain implementation (method bodies) as of all versions below Java 8.

Can we declare constructor as final?

No, a constructor can’t be made final. A final method cannot be overridden by any subclasses. As mentioned previously, the final modifier prevents a method from being modified in a subclass.

CAN interface have concrete methods?

Concrete methods in interfaces The simplest form of this feature is the ability to declare a concrete method in an interface, which is a method with a body. A class that implements this interface need not implement its concrete method.

Why static methods are not allowed in interface?

Java interface static method is part of interface, we can’t use it for implementation class objects. … This is because it’s not allowed in java, since Object is the base class for all the classes and we can’t have one class level static method and another instance method with same signature.

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.

What is difference between abstract class and interface?

Abstract class and interface both are used to achieve abstraction where we can declare the abstract methods. Abstract class and interface both can’t be instantiated….Difference between abstract class and interface.Abstract classInterface8) A Java abstract class can have class members like private, protected, etc.Members of a Java interface are public by default.8 more rows

Is if a keyword in Java?

if: Java if keyword tests the condition. It executes the if block if condition is true. implements: Java implements keyword is used to implement an interface.

Can we have main method in interface?

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.

Is it possible to declare method of the interface as private?

As of Java 9, methods in an interface can be private. A private method can be static or an instance method, but it cannot be a default method since that can be overridden.

Can we override static method?

Can we Override static methods in java? We can declare static methods with the same signature in the subclass, but it is not considered overriding as there won’t be any run-time polymorphism. Hence the answer is ‘No’.