今天在4.4看见一种比较奇怪的继承方式，不知道是我out了，还是out了

mark吧

 

public abstract class AtomicOperation implements Serializable {

  private static final long serialVersionUID = 1L;

  public static final AtomicOperation EXECUTE_ACTIVITY = new ExecuteActivity();

  public static final AtomicOperation PROPAGATE_TO_PARENT = new MoveToParentActivity();

  public static final AtomicOperation TRANSITION_TAKE = new TransitionTake();

  public static final AtomicOperation TRANSITION_START_ACTIVITY = new TransitionStartActivity();

  public static final AtomicOperation EXECUTE_EVENT_LISTENER = new ExecuteEventListener();

  public static final AtomicOperation TRANSITION_END_ACTIVITY = new TransitionEndActivity();

  public abstract boolean isAsync(ExecutionImpl execution);

  public abstract MessageImpl createAsyncMessage(ExecutionImpl execution);

  public abstract void perform(ExecutionImpl execution);

 

  public static AtomicOperation parseAtomicOperation(String text) {

    if (text==null) {

      return null;

    }

    if (TRANSITION_END_ACTIVITY.toString().equals(text)) return TRANSITION_END_ACTIVITY;

    if (EXECUTE_EVENT_LISTENER.toString().equals(text)) return EXECUTE_EVENT_LISTENER;

    if (EXECUTE_ACTIVITY.toString().equals(text)) return EXECUTE_ACTIVITY;

    if (TRANSITION_TAKE.toString().equals(text)) return TRANSITION_TAKE;

    if (TRANSITION_START_ACTIVITY.toString().equals(text)) return TRANSITION_START_ACTIVITY;

    if (PROPAGATE_TO_PARENT.toString().equals(text)) return PROPAGATE_TO_PARENT;

    throw new JbpmException("invalid atomic operation text: "+text);

  }

}

 

在父类里包括六个静态的子类的实例！第一次遇到