public RegionInfo build() {
    return new MutableRegionInfo(tableName, startKey, endKey, split, regionId, replicaId, offLine);
  }
RegionInfo for first meta region You cannot use this builder to make an instance of the
{@link #FIRST_META_REGIONINFO}. Just refer to this instance. Also, while the instance is
actually a MutableRI, its type is just RI so the mutable methods are not available (unless you
go casting); it appears as immutable (I tried adding Immutable type but it just makes a mess).
hbase-client/src/main/java/org/apache/hadoop/hbase/client/RegionInfoBuilder.java