Can interface methods have parameters?

Can interface methods have parameters?

A Java interface is a bit like a Java class, except a Java interface can only contain method signatures and fields. A Java interface is not intended to contain implementations of the methods, only the signature (name, parameters and exceptions) of the method.

How do you implement another interface?

An interface can extend any number of interfaces but one interface cannot implement another interface, because if any interface is implemented then its methods must be defined and interface never has the definition of any method.

What is Interface implementation?

To declare a class that implements an interface, you include an implements clause in the class declaration. Your class can implement more than one interface, so the implements keyword is followed by a comma-separated list of the interfaces implemented by the class.

How many methods should be implemented in an interface?

At present, a Java interface can have up to six different types. Interfaces cannot be instantiated, but rather are implemented. A class that implements an interface must implement all of the non-default methods described in the interface, or be an abstract class.

CAN interface have private methods?

An interface can have private methods since Java 9 version. These methods are visible only inside the class/interface, so it’s recommended to use private methods for confidential code.

What is the purpose of the interface parameter?

The whole purpose of an interface is to specify methods that a class must define, that we can call: so they can be only public.

What are the two keywords for interface?

Interface methods are by default abstract and public. Interface attributes are by default public , static and final. An interface cannot contain a constructor (as it cannot be used to create objects)

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”.

Why is interface used?

Why do we use interface ? It is used to achieve total abstraction. Since java does not support multiple inheritance in case of class, but by using interface it can achieve multiple inheritance . It is also used to achieve loose coupling.

Is it compulsory to implement all methods of interface?

Yes, it is mandatory to implement all the methods in a class that implements an interface until and unless that class is declared as an abstract class. Implement every method defined by the interface.

CAN interface have methods?

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.

When to use interface with different method parameters?

An interface is supposed to be used as a way to abstract away the method calls from the implementation. My recommendation is to use the method with both parameters in the interface and just don’t use the ID argument in CLASSB or to not have an add method in the interface and just have different versions in each class.

Do you have to declare method parameters in interface declaration?

…for an method in an interface declaration, do you have to declare method parameters, or can they be left up to the class that implements the interface? You need to specify the method arguments in the interface, since these are part of the method signature.

How does an interface define an implementing class?

An interface defines a contract; an implementing class has to override all the methods of an interface. You are overloading the setSize method in your code because you are changing the parameters. Read the pages below on interfaces.

Is it bad to add a method to an interface?

Or, add both the original and overloaded method into the interface. This is a bad idea, it violates OO design and the idea behind an interface. An interface is supposed to be used as a way to abstract away the method calls from the implementation.