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Interfaces

 Locked after Sunday, February 3, 2019 11:30 PM EST.

1. Explain Java interface and its use in a few sentences. 
2. Write the code of one Java interface with one method.
3. Also write two Java classes that will implement the method of this interface, but each class will implement this method from the interface differently. Simply put System.out.println inside each method with different output to demonstrate different implementation.
4. Write a few sentences explaining your code and the expected result/output.

Answer 1

1. An Interface in Java is just like a class except, it only have static constants and abstract methods. Interface is a way to achieve total abstraction in Java. It is also known as the blueprint of a class. Since we cannot achieve multiple inheritance in Java using classes, interfaces are used to achieve multiple inheritance. All the methods of an interface are implicitly public and abstract.

To implement an interface in our class we use the term "implements" between class_name and interface_name.

2. *********Java Code for Interface with one method***********

interface Pet{

public void pet_sound();

}

*********************************

3. *************Code for 2 classes implementing same method from interface Pet****************

interface Pet{    //defining interface

public void pet_sound();    //abstract method

}

class Dog implements Pet {      //using Pet interface

public void pet_sound(){

System.out.println("The dog Barks: bow bow");

}

}

class Cat implements Pet {    //using Pet interface

public void pet_sound(){

System.out.println("The cat says: mews mews");

}

}

//to demonstrate the different implementations

class MainClass {
public static void main(String[] args) {
    Dog mydog = new Dog(); // Create a Dog object

    Cat mycat = new Cat(); // Create a Cat object

    mydog.pet_sound();

    mycat.pet_sound();
}
}

*******************************************************************

4. The Code is explained using the //comments.

The demonstrated output of the code is shown below: