Method call

src/DeferredGroup.java:96–99

(final T arg)

        this.index = index;
      }
      public T call(final T arg) {
        recordCompletion(arg, index);
        return arg;
      }
      public String toString() {
        return "notify #" + index + " DeferredGroup@"
          + DeferredGroup.super.hashCode();