Method add

future-java/src/main/java/io/trane/future/Promise.java:868–871

(final Continuation<T, ?> c)

abstract class Continuation<T, R> extends Promise<R> implements WaitQueue<T> {

  @Override
  public final WaitQueue<T> add(final Continuation<T, ?> c) {
    return new WaitQueueHeadTail<>(c, this);
  }

  @Override
  public final void forward(final Promise<T> target) {