Clean way in GWT/Java to wait for multiple asynchronous events to finish

Question

What is the best way to wait for multiple asynchronous callback functions to finish in Java before continuing. Specifically I\'m using GWT with AsyncCallback, but I think this i

Answer 1

I did something similar to @Sasquatch, but instead making use of a "CallbackCounter" object:

public class CallbackCounter {
    private int outstanding;
    private final Callback callback;
    private final String message;

    public CallbackCounter(int outstanding, Callback callback, String callbackMessage) {
        this.outstanding = outstanding;
        this.callback = callback;
        this.message = callbackMessage;
    }

    public void count() {
        if (--outstanding <= 0) {
            callback.onSuccess(message);
        }
    }
}

Then in my callback I just call:

counter.count();