Definations And Use :- Interface

What is Interface

An interface in java is a blueprint of a class.

Purposes of Interfaces

create loosely coupled software
support design by contract (an implementor must provide the entire interface)
allow for pluggable software
allow different objects to interact easily
hide implementation details of classes from each other
facilitate reuse of software
It is used to achieve total abstraction.

What is loosely coupled software

Tight coupling is when a group of classes are highly dependent on one another.

This scenario arises when a class assumes too many responsibilities, or when one concern is spread over many classes rather than having its own class.

Loose coupling is achieved by means of a design that promotes single-responsibility and separation of concerns.

A loosely-coupled class can be consumed and tested independently of other (concrete) classes.

Interfaces are a powerful tool to use for decoupling. Classes can communicate through interfaces rather than other concrete classes, and any class can be on the other end of that communication simply by implementing the interface.

Example of tight coupling:

class CustomerRepository {
    private readonly Database
    database;

    public CustomerRepository(Database database) {
        this.database = database;
    }

    public void Add(string CustomerName) {
        database.AddRow("Customer", CustomerName);
    }
}

class Database {
    public void AddRow(string Table, string Value) {
    }
}

class CustomerRepository {

private readonly Database

database;

public CustomerRepository(Database database) {

this.database = database;

}

public void Add(string CustomerName) {

database.AddRow("Customer", CustomerName);

}

class Database {

public void AddRow(string Table, string Value) {

}

Example of loose coupling:

interface IDatabase {
    void AddRow(string Table, string Value);
}

class CustomerRepository {
    private readonly IDatabase
    database;

    public CustomerRepository(IDatabase database) {
        this.database = database;
    }

    public void Add(string CustomerName) {
        database.AddRow("Customer", CustomerName);
    }
}

class Database extends IDatabase {
    public void AddRow(string Table, string Value) {
    }
}

interface IDatabase {

void AddRow(string Table, string Value);

}

class CustomerRepository {

private readonly IDatabase

database;

public CustomerRepository(IDatabase database) {