Java，在不知道参数的情况下强制执行方法

Question

I have an abstract class that performs basic operations, now I want to force every derived class to have a method "check", but the point is I know nothing about this method. For example, the abstract class:

public abstract class Service<T extends Transport> {

  public T getTransport(int id) { 
    [...] 
  }

  public abstract boolean checkTransport(T transport, ...);

}

and two implementing classes:

public ServiceAAA extends Service<ClassA> {

  public boolean checkTransport(ClassA t) {
    [...]
  }

}

public ServiceBBB extends Service<ClassB> {

  public boolean checkTransport(ClassB t, Integer value, Integer otherValue) {
    [...]
  }

}

The ServiceBBB needs two parameter to check the object t of class ClassB. Of course it's not working, is there a way to force the subclass to implement the checkTransport method without using the "Object ... " notation?

Answer 1

No, there isn't.

Let's pretend there were a way. How would you invoke this method, either from the abstract Service class, or from any call site that had a reference to this object typed as Service<...> ? There'd be no way of knowing what the specific subclass's method expects, and thus no way of invoking the method.

One way around this is to pass the checker in as a class to Service; that is, to use composition instead of inheritance. If you do that, you can have the checker's interface take no extra arguments at all (a Predicate might work, for instance), and the specific subclasses that implement that checker could have the arguments passed at construction time.