public List<RegionState> getRegionFailedOpen() {
    if (regionFailedOpen.isEmpty()) return Collections.emptyList();

    ArrayList<RegionState> regions = new ArrayList<RegionState>(regionFailedOpen.size());
    for (RegionFailedOpen r : regionFailedOpen.values()) {
      regions.add(r.getRegionStateNode().toRegionState());
    }
    return regions;
  }
Get the number of regions in transition.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/RegionStates.java