public void addToBackupSet(String name, String[] newTables) throws IOException {
    if (LOG.isTraceEnabled()) {
      LOG.trace("Backup set add: " + name + " tables [" + StringUtils.join(newTables, " ") + "]");
    }
    String[] union = null;
    try (Table table = connection.getTable(tableName)) {
      Get get = createGetForBackupSet(name);
      Result res = table.get(get);
      if (res.isEmpty()) {
        union = newTables;
      } else {
        res.advance();
        String[] tables = cellValueToBackupSet(res.current());
        union = merge(tables, newTables);
      }
      Put put = createPutForBackupSet(name, union);
      table.put(put);
    }
  }
Add backup set (list of tables)
@param name      set name
@param newTables list of tables, comma-separated
@throws IOException if a table operation fails
hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/impl/BackupSystemTable.java