public int hashCode() {
      return 42;
    }
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