RFR: JDK-815440: JRT filesystem loaded by JDK8 with URLClassLoader is not closable since JDK-8147460

[Xueming Shen]

Hi,

Please help review the change for JDK-8154403

issue: https://bugs.openjdk.java.net/browse/JDK-8154403
webrev: http://cr.openjdk.java.net/~sherman/8154403/webrev/

The direct trigger of the failure is that the test case is passing in a 
null as parameter
"env" to create a new jrt filesystem. The nio spec specifies that it 
will trigger NPE. The
existing implementation does not check the "null" and passes it directly 
into
JrtFileSystem's constructor, in which the "null" is interpreted as "a 
not closable jrt file
system" (A implementation detail).

The fix is to add the "null check" in the provider and pass in "empty 
map" in the test case.

Alan, the original jrtfs implementation throws UOE in 
JrtFileSystemProvider.getTheFileSystem(),
is it better to just "silently" ignore the close request for the 
"not-closable" jrt? I'm file with
either way though.

Thanks,
Sherman