@Test
public void testIsValueIn() {

    final Map<String, Integer> refMap = new LinkedHashMap<>();
    refMap.put("one", 1);
    refMap.put("two", 2);
    refMap.put("three", 3);
    Integer[] filtered = Stream.of(5, 1, 2, 3, 4)
            .filter(isValueIn(refMap).negate()).toArray(Integer[]::new);
    assertArrayEquals("filtered should contain 5 and 4", new Integer[]{5, 4}, filtered);
}