INTERFACES

·         An interface must be declared with the keyword interface

·         Interfaces are by default abstract

      i.e.:

          public interface Comparable

      is the same as:

          public abstract interface Comparable

·         All methods are by default public abstract although it does not have to be mentioned. So, notice the following declarations are equal:

      public void method();

      public abstract void method();

     Because interface methods are abstract, they cannot be marked final, strictfp, native and private.

     e.g. private void method() is incorrect.

·         All variables are public static final by default

          pubic int x = 3;

      is the same as:

          public final static int x = 3;

      Because variables are final you have to declare and initialize them, you can’t have in the

      interface something like this:

          pubic int x;