9.1

Interface Declarations

INTERFACES

9.1   Interface Declarations

An interface declaration specifies a new reference type:

InterfaceDeclaration:

InterfaceModifiers

opt

 interface

Identifier

ExtendsInterfaces

opt

InterfaceBody

A compile time error occurs if the

Identifier

naming an interface appears as the

name of any other class or interface in the same package. A compile time error

also occurs if the

Identifier

 naming an interface appears as the name by which a

class or interface is to be known via a single type import declaration ( 7.5.1) in

the compilation unit containing the interface declaration. In the example:

class Point { int x, y; }

interface Point { void move(int dx, int dy); }

a compile time error occurs because a

class

 and an

interface

 in the same pack 

age cannot have the same name.

9.1.1   Scope of an Interface Type Name

The

Identifier

 specifies the name of the interface and has as its scope the entire

package in which it is declared. This is the same scoping rule as for class type

names; see  8.1.1 for an example involving classes.

9.1.2   Interface Modifiers

An interface declaration may be preceded by

interface modifiers

:

InterfaceModifiers:

InterfaceModifier

InterfaceModifiers InterfaceModifier

InterfaceModifier: one of

public abstract

The access modifier

public

 is discussed in  6.6. A compile time error occurs if

the same modifier appears more than once in an interface declaration.

9.1.2.1

abstract

Interfaces

Every interface is implicitly

abstract

. This modifier is obsolete and should not

be used in new Java programs.

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