private List<HRegionLocation> filterReopened(MasterProcedureEnv env,
    List<HRegionLocation> regionsToCheck) {
    return regionsToCheck.stream().map(env.getAssignmentManager().getRegionStates()::checkReopened)
      .filter(l -> l != null).collect(Collectors.toList());
  }
Used for reopening the regions for a table.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/ReopenTableRegionsProcedure.java