Java Language Tutorial => Declaring and Implementing an Interface

Example

Declaration of an interface using the interface keyword:

public interface Animal {
    String getSound(); // Interface methods are public by default
}

Override Annotation

@Override
public String getSound() {
    // Code goes here...
}

This forces the compiler to check that we are overriding and prevents the program from defining a new method or messing up the method signature.

Interfaces are implemented using the implements keyword.

public class Cat implements Animal {

    @Override 
    public String getSound() {
        return "meow";
    }
}

public class Dog implements Animal {

    @Override
    public String getSound() {
        return "woof";
    }
}

In the example, classes Cat and Dog must define the getSound() method as methods of an interface are inherently abstract (with the exception of default methods).

Using the interfaces

Animal cat = new Cat();
Animal dog = new Dog();

System.out.println(cat.getSound()); // prints "meow"
System.out.println(dog.getSound()); // prints "woof"

PDF - Download Java Language for free

Previous Next

Java Language

Fastest Entity Framework Extensions

Example

Got any Java Language Question?

Java Language

Java Language Interfaces Declaring and Implementing an Interface

Fastest Entity Framework Extensions

Example

Got any Java Language Question?