Why run IterativeConnectedComponents is similar to the death cycle about gelly-streaming HOT 2 CLOSED

private void addToExistingComponent(long componentId, long toAdd, Collector<Tuple2<Long, Long>> out) {
		HashSet<Long> vertices = components.remove(componentId);
        vertices.add(toAdd);
        //System.out.println("************addToExistingComponent componentId=" + componentId + ",toAdd = " + toAdd);
		if (componentId >= toAdd) {
			// output and update component ID
			for (long v: vertices) {
				out.collect(new Tuple2<Long, Long>(v, toAdd));
			}

			components.put(toAdd, vertices);
		}
		else {
			components.put(componentId, vertices);
			out.collect(new Tuple2<Long, Long>(toAdd, componentId));

		}
	}