CLASSES

Superinterfaces

8.1.4

8.1.4   Superinterfaces

The optional

implements

 clause in a class declaration lists the names of inter 

faces that are

direct superinterfaces

 of the class being declared:

Interfaces:

implements

InterfaceTypeList

InterfaceTypeList:

InterfaceType

InterfaceTypeList

 ,

InterfaceType

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

InterfaceType:

TypeName

Each

InterfaceType

 must name an accessible ( 6.6) interface type, or a compile 

time error occurs. All interfaces in the current package are accessible. Interfaces

in other packages are accessible if the host system permits access to the package

( 7.4.4) and the interface is declared

public

.

A compile time error occurs if the same interface is mentioned two or more

times in a single

implements

 clause, even if the interface is named in different

ways; for example, the code:

class Redundant implements java.lang.Cloneable, Cloneable {

int x;

}

results in a compile time error because the names

java.lang.Cloneable

 and

Cloneable

 refer to the same interface.

An interface type

I

 is a

superinterface

 of class type

C

 if any of the following

is true:

I

 is a direct superinterface of

C

.

C

 has some direct superinterface

J

 for which

I

 is a superinterface, using the

definition of  superinterface of an interface  given in  9.1.3.

I

 is a superinterface of the direct superclass of

C

, using this definition recur 

sively.

A class is said to

implement

 all its superinterfaces.

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