Packages - The Java Language Specification - page 171

It is a compile-time error if the named package or type is not accessible (§ 6.6 ) .
It is not a compile-time error to name the current package or java.lang in a type-import-on-
demand declaration. The type-import-on-demand declaration is ignored in such cases.
Example 7.5.2-1. Type-Import-on-Demand
import java.util.*;
causes the simple names of all public types declared in the package java.util to be avail-
able within the class and interface declarations of the compilation unit. Thus, the
simple name Vector refers to the type Vector in the package java.util in all places in the
compilation unit where that type declaration is not shadowed (§ 6.4.1 ) or obscured
(§ 6.4.2 ) .
The declaration might be shadowed by a single-type-import declaration of a type
whose simple name is Vector ; by a type named Vector and declared in the package to
which the compilation unit belongs; or any nested classes or interfaces.
The declaration might be obscured by a declaration of a field, parameter, or local vari-
able named Vector .
(It would be unusual for any of these conditions to occur.)
Two or more type-import-on-demand declarations in the same compilation unit may name
the same type or package. All but one of these declarations are considered redundant; the
effect is as if that type was imported only once.
If a compilation unit contains both a type-import-on-demand declaration and a static-
import-on-demand declaration (§ 7.5.4 ) that name the same type, the effect is as if the static
member types of that type (§ 8.5 , § 9.5 ) were imported only once.
7.5.3. Single-Static-Import Declarations
A single-static-import declaration imports all accessible static members with a given simple
name from a type. This makes these static members available under their simple name in
the class and interface declarations of the compilation unit in which the single-static-import
declaration appears.
SingleStaticImportDeclaration:
import static TypeName . Identifier ;
The TypeName must be the canonical name (§ 6.7 ) of a class type, interface type, enum
type, or annotation type.