[b84 regression?] stream.parallel()/sequential() return the stream itself when they are not expected to

Dmitry Bessonov dmitry.bessonov at oracle.com
Fri Apr 5 08:40:49 PDT 2013

Consider the following code sample:

   Stream<String> stream = Arrays.asList("a", "b", "c").stream();
   out.println("stream = " + stream);
   out.println("stream.isParallel() = " + stream.isParallel());
   out.println("stream.parallel() = " + stream.parallel());
   out.println("stream.parallel() = " + stream.parallel());
   out.println("stream.parallel().isParallel() = " + 

With b83 a
"java.lang.IllegalStateException: Stream is already linked to a child 
is thrown on attempt to double link a stream.

With b84 the output is quite unexpected:

stream = java.util.stream.ReferencePipeline$Head at 1f3c5b5
stream.isParallel() = false
stream.parallel() = java.util.stream.ReferencePipeline$Head at 1f3c5b5
stream.parallel() = java.util.stream.ReferencePipeline$Head at 1f3c5b5
stream.parallel().isParallel() = true

If it's not a regression
then it looks like the spec
for java.util.stream.BaseStream.parallel() deserves to be updated.

The same issue takes place with parallel->sequential
stream transformation so the spec for sequential() needs an update too.


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