Interface Definition

An interface definition looks like this:

interface InterfaceName
{
  constant definitions

  method declarations (without implementations).
}

A method declaration is simply an access modifier, a return type, and a method signature followed by a semicolon.

This looks somewhat like a class definition. But no objects can be constructed from it. However, objects can be constructed from a class that implements an interface. A class implements an interface by doing this:

class SomeClass extends SomeParent implements interfaceName
{

}

A class always extends just one parent but may implement several interfaces.