private static int joint(Map<?, ?> m1, Map<?, ?> m2) {
    if (m1.size() < m2.size()) {
      return -1;
    } else if (m2.size() < m1.size()) {
      return 1;
    }
    Collection<Object> c3 = new ArrayList<>();
    c3.addAll(m1.keySet());
    c3.removeAll(m2.keySet());
    if (c3.size() > 0) {
      return -1;
    }
    c3.addAll(m2.keySet());
    c3.removeAll(m1.keySet());
    if (c3.size() > 0) {
      return 1;
    }
    return 0;
  }
Returns -1 if m1 is missing a key in m2, 1 if m2 is missing a key in m1, or 0 is they contain
the exact same keys.

@throws NullPointerException if either c1 or c2 is null
geode-core/src/integrationTest/java/org/apache/geode/internal/offheap/OffHeapValidationJUnitTest.java