PACKAGES

Single Type Import Declaration

7.5.1

7.5.1   Single Type Import Declaration

A

single type import declaration

imports a single type by giving its fully qualified

name, making it available under a simple name in the class and interface declara 

tions of its compilation unit.

SingleTypeImportDeclaration:

import

TypeName

 ;

The

TypeName

 must be the fully qualified name of a class or interface type; a

compile time error occurs if the named type does not exist. If the named type is

not in the current package, then it must be accessible ( 6.6) in an accessible

package and declared

public

 ( 8.1.2,  9.1.2) or a compile time error occurs.

The example:

import java.util.Vector;

causes the simple name

Vector

 to be available within the class and interface dec 

larations in a compilation unit. Thus, the simple name

Vector

 refers to the type

Vector

 in the package

java.util

 in all places where it is not hidden ( 6.3) by a

declaration of a field, parameter, or local variable with the same name.

If two single type import declarations in the same compilation unit attempt to

import types with the same simple name, then a compile time error occurs, unless

the two types are the same type, in which case the duplicate declaration is ignored.

If another type with the same name is otherwise declared in the current compila 

tion unit except by a type import on demand declaration ( 7.5.2), then a compile 

time error occurs.

So the sample program:

import java.util.Vector;

class Vector { Object[] vec; }

causes a compile time error because of the duplicate declaration of

Vector

, as

does:

import java.util.Vector;

import myVector.Vector;

where

myVector

 is a package containing the compilation unit:

package myVector;

public class Vector { Object[] vec; }

The compiler keeps track of types by their fully qualified names ( 6.7). Sim 

ple names and fully qualified names may be used interchangeably whenever they

are both available.

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