We learn about the importance of “Interface” feature of OOP:
In Java, an interface is a way to achieve abstraction. It’s like a blueprint of a class, defining a set of methods that any class implementing the interface must provide. Think of it as a contract that a class agrees to follow.
Interface declaration
An interface is declared using the interface keyword. It can have abstract methods (methods without a body) and constant variables.
/**
* This only has the skeleton, you must implement the method in the target class
* @author azmeer
*/
public interface Animal {
void makeSound(); // Abstract method
String getName(); // Another abstract method
}Interface implementation
A class implements an interface using the implements keyword. The class must provide concrete implementations (with a body) for all methods declared in the interface.
/**
*
* @author azmeer
*/
public class Dog implements Animal{
@Override
public void makeSound() {
System.out.println("Woof! Woof!");
}
@Override
public String getName() {
return "Dog";
}
}Another class using the ‘Animal’ interface.
/**
* Must override the interface methods and implement here
* @author azmeer
*/
public class Cat implements Animal {
@Override
public void makeSound() {
System.out.println("Meow");
}
@Override
public String getName() {
return "Cat";
}
}Tester
/**
* Make objects out of class for testing
* @author azmeer
*/
public class W11aInterface1 {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
System.out.println("Java Interface tester");
Dog tommy = new Dog();
tommy.makeSound();
System.out.println(tommy.getName());
Cat poosa = new Cat();
poosa.makeSound();
System.out.println(poosa.getName());
}
}