protected StringBuilder appendTo(StringBuilder builder) {
    return jobId.appendTo(builder).
                 append(SEPARATOR).
                 append(CharTaskTypeMaps.getRepresentingCharacter(type)).
                 append(SEPARATOR).
                 append(idFormat.format(id));
  }
@Test
  public void testAppendTo() {
    JobID jobId = new JobID("1234", 1);
    StringBuilder builder = new StringBuilder();

    for (TaskType type : TaskType.values()) {
      builder.setLength(0);
      TaskID taskId = new TaskID(jobId, type, 0);
      String str = String.format("_1234_0001_%c_000000",
          TaskID.getRepresentingCharacter(type));

      assertEquals("The appendTo() method appended the wrong value",
          str, taskId.appendTo(builder).toString());
    }

    try {
      new TaskID().appendTo(null);
      fail("The appendTo() method allowed a null builder");
    } catch (NullPointerException ex) {
      // Expected
    }
  }