What is the use of an interface?

An interface is a guarantee that a class will have certain methods. This is useful when passing arguments to methods. In code terms it will allow a method to accept arguments based on the interface rather than being restricted to objects of a certain type. For example:

       public void methodFoo (Set<Strings> someStrings) {
           doSomething(someStrings);
      }

This method is able to accept any argument that implements the Set interface (and then do something with it). That means it can take a TreeSet as well as HashSet. If had to do something similar without using interfaces we would have to duplicate code. The above example would turn into something like this:

      public void methodFoo (TreeSet<Strings> someStrings) {
          doSomething(someStrings);
      }

     public void methodFoo (HashSet<Strings> someStrings) {
         doSomething(someStrings);
     }

If you wanted more types of sets you would have to have more methods.

Hope this help!

Jiten;

Welcome to Treehouse!

Great question. A Java interface is a bit like a class, except a Java interface can only contain method signatures and fields. An Java interface cannot contain an implementation of the methods, only the signature (name, parameters and exceptions) of the method.

Take a look at the official documentation and post back if you need more information.

Happy coding,

Ken