Defining an Interface

Purpose:

To declare the responsibilities of an implementation.

Mechanics:

<modifiers> interface
<interface name> {

/* Abstract methods and class
constants declared here */

}

Example:

public interface myInterface
{

int MY_CONSTANT = 10;

void myMethod();

}

Usage:

<modifiers> is an optional space-separated list of valid interface modifiers. All interfaces are implicitly abstract and inclusion of that modifier is optional.
<interface name>is any valid identifier which is unique to the current scope.
All methods declared in an interface are implicitly abstract and public.
All instance variables declared in an interface are implicitly public, static, and final, and therefore must include an initial value in the declaration.
Inlcusion of implicit modifiers is optional.
Variables may be declared of type <interface name> and defined to be of a class that implements the interface. Such references respond to all methods declared in the interface.

Restrictions:

A method declared in an interface cannot have a default implementation, nor can it be declared

private, protected,
static, final,

or synchronized. An instance variable declared in an interface is considered a class constant. It cannot be declared private, protected, or synchronized.

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