Java Essentials - Interfaces in java

Interfaces in Java

So now what is one interface? Interface will have only the function prototypes

And all the variables which will be defined under the interface with initialization

will be treated as a constant type of variable. So in case of interface, we don't write the function bodies

We'll be writing only the function prototypes. So that's why you can say that interfaces are going to contain only the abstract methods

So there is a special features. a special features of interface which is making it different from the class let us

suppose we're going to organize one party for our friends in that case we are hiring

or we are doing the food preparation outsource to one of the catarers so we are

making a menu that these are the items will be there in our respective menu so

whenever you were making a deal with the caterer so in that case we are telling

that we required food number one food number two food number three and say food

number four we are not mentioning what is the respective recipe to prepare those foods

that means we are defining only the function prototypes not defining the function

bodies now it will be the headache or it will be the responsibility of the respective caterer to make the food ready according to the recipe they might be knowing and they should present that that food in front of

us when the party will be on so that is a concept so that is here in case of interfaces we

will be writing different methods only the prototypes will be written not the respective method

bodies so let us suppose we are going to define one interface that is a bank account in that case

we're having some set of methods will be there what are the operations that you can

perform on the bank account that is the account balance check it is one

method depositing the depositing the money that is another method withdrawing the

money that is another method checking the current balance that is might be the

another method so you see we're having multiple different operations that you can

carry out on a bank account so whenever we define one interface against this bank account

will be mentioning this function prototypes without their respective bodies. So that is the concept of interface

An interface is a collection of abstract methods, that means only the prototypes will be there

A class can implement an interface and we will use the word implements remember implements keyword to use an interface That means to implement one interface in a class I require to use the keyword implements

We cannot instantiate an interface because the methods are not defined and it does not contain any constructor

Multiple inheritance concepts can be implemented using this interface concepts in Java

When a class is implementing an interface, all the methods which are present in the interface

must be defined in the respective implementing class. So let us go for one practical demonstration where we'll be showing all these concepts

into details, writing the codes, executing and all to clear your conception better

In this demonstration we shall discuss and we shall write code on interface in Java

So at first we are going for one interface. definition so my interface name is my interface one so public interface

my interface one I just defining two functions here from Java 1 onwards interface can also contain function with the function

bodies if they are of type default or static so let us define such functions here

Thank you. So in this way we have defined my interface one

Let us go on defining my interface 2 which will inherit it which will inherit my

interface 1 so I'm going to define another one