With b83-lambda the following

System.out.println("isParallel = " +Arrays.asList(1, 2, 3).stream().parallel().isParallel());

prints out

isParallel = false

The following JCK tests fail due to this issue:

api/java_util/BitSet/Stream.html#Stream[checkParallel]
api/java_util/ArrayDeque/Stream.html#Stream[checkParallel]
api/java_util/Arrays/StreamTests.html#StreamTests[checkParallel]
api/java_util/ArrayList/Stream.html#Stream[checkParallel]
api/java_util/stream/Streams/EmptyDoubleStream.html#EmptyDoubleStream[checkParallel]
api/java_util/stream/Streams/EmptyIntStream.html#EmptyIntStream[checkParallel]
api/java_util/stream/Streams/EmptyLongStream.html#EmptyLongStream[checkParallel]
api/java_util/stream/Streams/EmptyStream.html#EmptyStream[checkParallel]
api/java_util/Arrays/DoubleStreamTests.html#DoubleStreamTests[checkBoxed]
api/java_util/Arrays/DoubleStreamTests.html#DoubleStreamTests[checkParallel]
api/java_util/stream/Streams/index.html#GenerateRepeated[checkParallel]
api/java_util/stream/Streams/Iterate.html#Iterate[checkParallel]
api/java_util/LinkedHashSet/Stream.html#Stream[checkParallel]
api/java_util/LinkedList/index.html#Stream[checkParallel]
api/java_util/Arrays/LongStreamTests.html#LongStreamTests[checkParallel]
api/java_util/Arrays/LongStreamTests.html#LongStreamTests[checkDoubles]
api/java_util/Arrays/LongStreamTests.html#LongStreamTests[checkBoxed]
api/java_util/stream/Streams/index.html#GenerateCycled[checkParallel]
api/java_util/HashSet/Stream.html#Stream[checkParallel]
api/java_util/stream/Streams/ConcatInfinite.html#ConcatInfinite[checkParallel]
api/java_util/Arrays/StreamOffsetLengthTests.html#StreamOffsetLengthTests[checkParallel]