Google 工程师写的 Java 代码片段，你能看懂其中的奥妙么？

片断 1：

public  A appendTo(A appendable, Iterator parts) throws IOException {
  checkNotNull(appendable);
  if (parts.hasNext()) {
	appendable.append(toString(parts.next()));
	while (parts.hasNext()) {
	  appendable.append(separator);
	  appendable.append(toString(parts.next()));
	}
  }
  return appendable;
}
​

片断 2：

public final  A appendTo(A appendable, @Nullable Object first, @Nullable Object second, Object... rest) throws IOException {
  return appendTo(appendable, iterable(first, second, rest));
}

private static Iterable iterable(final Object first, final Object second, final Object[] rest) {
  checkNotNull(rest);
  return new AbstractList() {
	@Override public int size() {
	  return rest.length + 2;
	}

	@Override public Object get(int index) {
	  switch (index) {
		case 0:
		  return first;
		case 1:
		  return second;
		default:
		  return rest[index - 2];
	  }
	}
  };
}
​