Names - The Java Language Specification - page 149

If a method name is of the form Q.Id , then Q has already been classified as a package name,
a type name, or an expression name:
• If Q is a package name, then a compile-time error occurs.
• Otherwise, Q is a type name or an expression name.
Id is the method name to be used for method invocation.
If Q is a type name, then Id must name at least one static method of the type Q , or a
compile-time error occurs by the rules of § 15.12 .
If Q is an expression name, then let T be the type of the expression Q . Id must
name at least one method of the type T , or a compile-time error occurs by the rules
of § 15.12 .
Like expression names, method names may be qualified by type names, but
not by types in general. The implications are similar to those for expression
names as discussed in § 6.5.6.2 .
6.6. Access Control
The Java programming language provides mechanisms for access control , to prevent the
users of a package or class from depending on unnecessary details of the implementation
of that package or class. If access is permitted, then the accessed entity is said to be access-
ible .
Note that accessibility is a static property that can be determined at compile time; it de-
pends only on types and declaration modifiers.
Qualified names are a means of access to members of packages and reference types. When
the name of such a member is classified from its context (§ 6.5.1 ) as a qualified type name
(denoting a member of a package or reference type, § 6.5.5.2 ) or a qualified expression
name (denoting a member of a reference type, § 6.5.6.2 ) , access control is applied.
For example, a single-type-import statement (§ 7.5.1 ) must use a qualified type name,
so the type name being imported must be accessible from the compilation unit con-
taining the import statement. As another example, a class declaration may use a qual-
ified type name for a superclass (§ 8.1.5 ), and again the qualified type name must be
accessible.
Some obvious expressions are “missing” from context classification in § 6.5.1 : field
access on a Primary (§ 15.11.1 ) , method invocation on a Primary (§ 15.12 ), and the
instantiated class in a qualified class instance creation (§ 15.9 ). Each of these expres-
sions uses identifiers, rather than names, for the reason given in § 6.2 . Consequently,