VectorTests fail on Java >= 9 #11

The VectorTest (test2, test4, test5, test6) fails on Java >= 9 with message:

java.lang.RuntimeException: Unsound results: [MustBe [s (typestate.tests.VectorTest.<typestate.tests.VectorTest: void test2()>) @ mustBeInAcceptingState(s) in state ACCEPTING]]

Running on Java 8 the tests succeed, but on Java >= 9 the tests fail. Needs further investigation. Many java.util.Collection's implementations have been changed between Java 8 and Java 9. We need to inspect the differences of the java.util.Vector implementations and their effect on Boomerang to see why those tests suddenly fail.