public long mappingCount() {
    long n = sumCount();
    return (n < 0L) ? 0L : n; // ignore transient negative values
  }
Returns the number of mappings. This method should be used instead of {@link #size} because a
CompactConcurrentHashSet2 may contain more mappings than can be represented as an int. The
value returned is an estimate; the actual count may differ if there are concurrent insertions
or removals.

@return the number of mappings
@since Geode 1.0
geode-core/src/main/java/org/apache/geode/internal/concurrent/CompactConcurrentHashSet2.java