Question

So I am thinking trough a little project. And a problem I seem to encounter is :
I have Class A which contains an instance of class C and a list of instances of class B.
Each class contains a timer. I need to execute a class C method when that timer fires an event.

public class A
{
  C C1 = new C(this);
  public ArrayList<B> B1= new ArrayList<>();        
}

so when timer expires I need to fire something like:

C1.method()

Answer 1

Very basic / easy approach: Implemenbt a simple subscribe / publish framework.

1. Create an interface that defines a call back method.
2. Implement the callback interface in Class C.
3. provide a means by which class C anc register the callback with each instance of Class B; do so.
4. When the timer, in a specific instance of class b, fires, call the callback.

For eaxmple:

public interface BlammyHoot
{
  void hoot(); // this is the call back.
}

public class C implements BlammyHoot
{
  public void hoot()
  {
    // implement the callbe method here.
  }
}

public class B
{
  private List<BlammyHoot> hootList = new LinkedList<BlammyHoot>();

  public void registerBlammyHoot(final BlammyHoot theHoot)
  {
    if (theHoot != null)
    {
      hootList.add(theHoot);
    }
  }

  public void respondToTimerTimeout()
  {
    for (BlammyHoot hootElement : hootList)
    {
      hootElement.hoot();
    }
  }
}

Caveat: zero testing performed on the obove java code (including, but not limited to, I did not compile it).