The alias "ASCII7" which refers to US-ASCII (aka, ANSI_X3.4-1986) is missing
from the list of registered aliases for the NIO charset implementation
included in J2SE 1.4.0 and 1.4.1. Charset.forName("ASCII7") will not
return back an instance on sun.nio.cs.US_ASCII whereas the alias will
work when using java.lang or java.io APIs, eg String getBytes("ASCII7")
will encode using "US-ASCII".

This inconsistency should be iron out and the alias should be added to
the list of provided aliases within the core J2SE platform J2SE
CharsetProvider implementation.