public Map.Entry<VersionTag, T> take() {
    if (tombstoneMap.isEmpty()) {
      // if there are no more entries, return null;
      return null;
    } else {
      // Otherwise, look at all of the members and find the tag with the
      // lowest timestamp.
      long lowestTimestamp = Long.MAX_VALUE;
      TreeMap<VersionTag, T> lowestMap = null;
      for (TreeMap<VersionTag, T> memberMap : tombstoneMap.values()) {
        VersionTag firstTag = memberMap.firstKey();
        long stamp = firstTag.getVersionTimeStamp();
        if (stamp < lowestTimestamp) {
          lowestTimestamp = stamp;
          lowestMap = memberMap;
        }
      }
      if (lowestMap == null) {
        return null;
      }
      // Remove the lowest entry
      Entry<VersionTag, T> result = lowestMap.firstEntry();
      lowestMap.remove(result.getKey());
      if (lowestMap.isEmpty()) {
        // if this is the last entry from a given member,
        // the map for that member
        tombstoneMap.remove(result.getKey().getMemberID());
      }

      return result;
    }
  }
Remove a version tag from the map.
geode-core/src/main/java/org/apache/geode/internal/cache/OrderedTombstoneMap.java