INTERFACES

Interface Body and Member Declarations

9.1.4

9.1.3   Superinterfaces

If an

extends

 clause is provided, then the interface being declared extends each

of the other named interfaces and therefore inherits the methods and constants of

each of the other named interfaces. These other named interfaces are the

direct

superinterfaces

 of the interface being declared. Any class that

implements

 the

declared interface is also considered to implement all the interfaces that this inter 

face

extends

 and that are accessible to the class.

ExtendsInterfaces:

extends

InterfaceType

ExtendsInterfaces

 ,

InterfaceType

The following is repeated from  4.3 to make the presentation here clearer:

InterfaceType:

TypeName

Each

InterfaceType

in the

extends

 clause of an interface declaration must

name an accessible interface type; otherwise a compile time error occurs.

A compile time error occurs if there is a circularity such that an interface

directly or indirectly extends itself.

There is no analogue of the class

Object

 for interfaces; that is, while every

class is an extension of class

Object

, there is no single interface of which all

interfaces are extensions.

The

superinterface

relationship is the transitive closure of the direct super 

interface relationship. An interface

K

 is a superinterface of interface

I

 if either of

the following is true:

K

 is a direct superinterface of

I

.

There exists an interface

J

 such that

K

 is a superinterface of

J

, and

J

 is a

superinterface of

I

, applying this definition recursively.

Interface

I

 is said to be a

subinterface

of interface

K

 whenever

K

is a superinter 

face of

I

.

9.1.4   Interface Body and Member Declarations

The body of an interface may declare members of the interface:

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