Question

(Java) Please describe how API's can be created using abstract classes, interfaces and regular classes.

Answer 1

Interfaces:

Interfaces won't have method implementation but only method declaration. All the methods in interfaces are pub;ic abstract (default). Some class has to inherit the interface and define the implementation of the method.

eg: Interface Car { void PrintColor(); void PrintNumberOfGears();}

Public class BlueCar implements Car

{

public void PrintColor() {System.out.println("Color is Blue");}

public void PrintNumberOfGears() {System.out.println("Number of Gears are 5");}

}

Abstract Class:

Abstract Methods are similar to normal classes but it can have abstract as well as concrete methods. Abstract methods has to be inherited and defined.

example : public abstract class Students

{

public void PrintMarks() {System.out.println("Printing Marks");} //concrete method

public abstract void PrintEmpId { } //abstract method

} //Note the abstract keyword

Regular Classes:

Regular classes cannot have abstract methods , but only concrete methods. See the above abstract class example and take only the concrete method. as an example.

eg: public class Employee{}

APIs are also methods. So all of the above discussed details are good for creating APIs