Types should always be imported by their canonical name. The canonical name of a top-level class is the fully-qualified name of the package, followed by a ‘.’, followed by the name of the class. The canonical name of a member class is the canonical name of its declaring class, followed by a ‘.’, followed by the name of the member class.
Fully-qualified member class names are not guaranteed to be canonical. Consider some member class M declared in a class C. There may be another class D that extends C and inherits M. Therefore M can be accessed using the fully-qualified name of D, followed by a ‘.’, followed by ‘M’. Since M is not declared in D, this name is not canonical.
The JLS §7.5.3 requires all single static imports to start with a canonical type name, but the fully-qualified name of the imported member is not required to be canonical.
Importing types using non-canonical names is unnecessary and unclear, and should be avoided.
Example:
package a;
class One {
static class Inner {}
}
package a;
class Two extends One {}
An import of Inner should always refer to it using the canonical name
a.One.Inner, not a.Two.Inner.