https://www.cnblogs.com/fireflyupup/p/4875130.html
Collection
List
Collection introduced on the basis of the order of concept, location accuracy; allows the same elements. On the list traversal iteration is usually better than the index. Special ListIterator iterator allows element insertion, substitution, two-way access, starting from the list of developing position (According to acquire index index position of the element). Get method is not implemented.
AbstractList
List some of the ways to achieve the support of random access . lastIndexOf able to develop through special iterator starting position to achieve from the property after traversal. Directly by specifying the location, with special iterator find