Interfaces

An interface is a collection of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface.

An interface is similar to a class in the following ways:

• An interface can contain any number of methods.
• An interface is written in a file with a .java extension, with the name of the interface matching the name of the file.
• The bytecode of an interface appears in a .class file.
• Interfaces appear in packages, and their corresponding bytecode file must be in a directory structure that matches the package name.
  
  
  However, an interface is different from a class in several ways, including:
  • You cannot instantiate an interface.
  • An interface does not contain any constructors.
  • All of the methods in an interface are abstract.
  • An interface cannot contain instance fields. The only fields that can appear in an interface must be declared both static and final.
  • An interface is not extended by a class; it is implemented by a class.
  • An interface can extend multiple interfaces.
    
    
    
    
    
    
    FOR EXAMPLE::

    
    

    
    

    interface Animal {
    
     public void eat();
     public void travel();
    }

    
    public class MammalInt implements Animal{
    
       public void eat(){
          System.out.println("Mammal eats");
       }
    
       public void travel(){
          System.out.println("Mammal travels");
       } 
    
       public int noOfLegs(){
          return 0;
       }
    
       public static void main(String args[]){
          MammalInt m = new MammalInt();
          m.eat();
          m.travel();
       }
    }