@Override
  public Future<Void> modifyColumnFamilyAsync(TableName tableName,
    ColumnFamilyDescriptor columnFamily) throws IOException {
    return admin.modifyColumnFamily(tableName, columnFamily);
  }
The {@link Admin} implementation which is based on an {@link AsyncAdmin}.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AdminOverAsyncAdmin.java