byte[][] getAllColumns(Table table) throws IOException {
    ColumnFamilyDescriptor[] cds = table.getDescriptor().getColumnFamilies();
    byte[][] columns = new byte[cds.length][];
    for (int i = 0; i < cds.length; i++) {
      columns[i] = Bytes.add(cds[i].getName(), KeyValue.COLUMN_FAMILY_DELIM_ARRAY);
    }
    return columns;
  }
Returns a list of all the column families for a given Table.
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift/ThriftHBaseServiceHandler.java