As we all know, method Charset.forName(String) is to get an Charset instance by a canonical name or an alias.
I tested the following codes

System.out.println(StandardCharsets.UTF_8);
System.out.println(Charset.forName(StandardCharsets.UTF_8.name()));

System.out.println(StandardCharsets.UTF_16);
System.out.println(Charset.forName(StandardCharsets.UTF_16.name()));

As I expected, the result is

UTF-8
UTF-8
UTF-16
UTF-16

So I supposed that if I give the code Charset.forName(UnknownCharset.getInstance().name()) OR Charset.forName("void"), I would get an UnknownCharset instance. But exception happends

Exception in thread "main" java.nio.charset.UnsupportedCharsetException: void
         at java.nio.charset.Charset.forName(Charset.java:536)
         at Test.main(Test.java:13)