@Override
        public void execute(final Vertex vertex, final Messenger messenger, final Memory memory) {
            if (memory.isInitialIteration()) {
                assertFalse(memory.exists("m1"));
                assertTrue(memory.exists("m2"));
                assertTrue(memory.get("m2"));
                assertFalse(memory.exists("m3"));
                assertTrue(memory.exists("m4"));
                assertEquals(0, memory.<Integer>get("m4").intValue());
                memory.add("m1", false);
                memory.add("m2", true);
                memory.add("m3", 1l);
                memory.add("m4", -1);
            } else {
                assertFalse(memory.exists("m1")); // no broadcast
                assertTrue(memory.exists("m2"));
                assertFalse(memory.exists("m3")); // no broadcast
                assertTrue(memory.exists("m4"));
                try {
                    assertFalse(memory.get("m1"));
                    fail();
                } catch (final Exception e) {
                    validateException(Memory.Exceptions.memoryDoesNotExist("m1"), e);
                }
                assertTrue(memory.get("m2"));
                try {
                    assertEquals(6l, memory.<Long>get("m3").longValue());
                    fail();
                } catch (final Exception e) {
                    validateException(Memory.Exceptions.memoryDoesNotExist("m3"), e);
                }
                assertEquals(-6l, memory.<Integer>get("m4").intValue());
                ///
                memory.add("m1", true);
                memory.add("m2", true);
                memory.add("m3", 2l);
                memory.add("m4", -2);
            }
        }
Javadoc for {@code ConcurrentSkipListSet} includes this little note: "Beware that, unlike in most
collections, the size method is not a constant-time operation." Doing a traversal of elements will yield
the correct count. Java 11 upgrade seemed to force this failure consistently.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/computer/GraphComputerTest.java