@Override
  public int size() {
    checkReadiness();
    checkForNoAccess();
    discoverJTA();
    boolean isClient = imageState.isClient();
    if (isClient) {
      lockRIReadLock();
    }
    try {
      return entryCount();
    } finally {
      if (isClient) {
        unlockRIReadLock();
      }
    }
  }
(description copied from entryCount() Returns the number of entries in this region. Note that
because of the concurrency properties of the {@link RegionMap}, the number of entries is only
an approximate. That is, other threads may change the number of entries in this region while
this method is being invoked.

@see LocalRegion#entryCount()
geode-core/src/main/java/org/apache/geode/internal/cache/LocalRegion.java