private static void addColumns(Scan scan, String columns) {
    String[] cols = columns.split(" ");
    for (String col : cols) {
      addColumn(scan, Bytes.toBytes(col));
    }
  }
Convenience method to parse a string representation of an array of column specifiers.
@param scan    The Scan to update.
@param columns The columns to parse.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/TableInputFormat.java