这这这没有因果关系啊：实现了 RandomAccess 接口，因此支持随机访问。

而且应该是 快速随机访问。
Marker interface used by <tt>List</tt> implementations to indicate that
 * they support fast (generally constant time) random access.  The primary
 * purpose of this interface is to allow generic algorithms to alter their
 * behavior to provide good performance when applied to either random or
 * sequential access lists.