Set frame has two interfaces are the most advanced subclass collectio and map collection list set are
Which implement a list of implementation classes have arraylist vector linkedlist, arraylist suitable for single-threaded thread-unsafe find data fast, slow additions and deletions to the data, vector for multi-threaded thread-safe data to find data fast additions and deletions to slow, linkedlist doubly linked list structure thread safe Find data additions and deletions to the slow data quickly.
Wherein the set implementation class has implemented treeSet hashSet t, treeSet binary tree data structure is disordered data, can not be repeated, can not be empty; HashSet data can not be repeated, may be null values hashhmap principle is that the key can not be duplicated,
map implementation class has hashmap and hashtable hashmap high thread-unsafe efficiency, hashtable is thread-safe, low efficiency.