@Override
  public String toString() {
    StringBuilder stringBuilder = new StringBuilder();
    stringBuilder.append('[');
    int numColumns = _columnNames.length;
    for (int i = 0; i < numColumns; i++) {
      stringBuilder.append(_columnNames[i]).append('(').append(_columnDataTypes[i]).append(')').append(',');
    }
    stringBuilder.setCharAt(stringBuilder.length() - 1, ']');
    return stringBuilder.toString();
  }
@Test
  public void testToString() {
    DataSchema dataSchema = new DataSchema(COLUMN_NAMES, COLUMN_DATA_TYPES);
    Assert.assertEquals(dataSchema.toString(),
        "[int(INT),long(LONG),float(FLOAT),double(DOUBLE),string(STRING),object(OBJECT),int_array(INT_ARRAY),"
            + "long_array(LONG_ARRAY),float_array(FLOAT_ARRAY),double_array(DOUBLE_ARRAY),string_array(STRING_ARRAY),"
            + "boolean_array(BOOLEAN_ARRAY),timestamp_array(TIMESTAMP_ARRAY),bytes_array(BYTES_ARRAY)]");
  }