public EntrySet entrySet()
    {
        if (null == entrySet)
        {
            entrySet = new EntrySet();
        }

        return entrySet;
    }
@Test
    void removeIfOnEntrySetThrowsUnsupportedOperationException()
    {
        final Predicate<Map.Entry<Integer, String>> filter = (entry) -> true;

        final UnsupportedOperationException exception =
            assertThrowsExactly(UnsupportedOperationException.class, () -> cache.entrySet().removeIf(filter));
        assertEquals("Cannot remove from EntrySet", exception.getMessage());
    }