What is an Interface in Java and How Does it Work?

What is an Interface in Java?

An interface is a special type of abstract class used in object-oriented programming languages like Java.

In Java, an interface is defined as follows:

interface Interface {
    // Declare abstract methods
}

Unlike abstract classes, interfaces cannot implement methods. Instead, they define abstract methods that must be implemented in the classes that implement the interface. Here's an example of an interface:

interface Shape {
    void draw();
}

To use an interface, a class must implement it, which means it must provide implementations for all the abstract methods in the interface. Multiple classes can implement the same interface, and a class can implement multiple interfaces.

For example:

class Circle implements Shape {
    public void draw() { System.out.println("I'm a circle."); }
}

class Square implements Shape {
    public void draw() { System.out.println("I'm a square."); }
}

Now, you can use the Shape interface as follows:

Shape shape = new Circle();
shape.draw(); // Prints: I'm a circle.

Interfaces are used widely in Java for loose coupling and polymorphism. They allow classes to define common behaviors without explicitly specifying a concrete implementation. This promotes code reusability, flexibility, and extensibility.

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