遇到for(;;),求个解释

今天看jdk1.6源码时AbstractCollection类里面有个toString方法，不知道里面的for是怎么循环的~那位大牛能解释一下嘛~

    public String toString() {
        Iterator<E> i = iterator();
	if (! i.hasNext())
	    return "[]";

	StringBuilder sb = new StringBuilder();
	sb.append('[');
	for (;;) {
	    E e = i.next();
	    sb.append(e == this ? "(this Collection)" : e);
	    if (! i.hasNext())
		return sb.append(']').toString();
	    sb.append(", ");
	}
    }

}