List and set

List Orderly , repeatable

List Implementation class of

1. ArrayList By name , As you can see , The bottom layer uses Array , Quick query , Add or delete slowly .
2. LinkedList Know by name , The bottom layer uses linked lists , Slow query , Additions and deletions quickly .
3. Vector The bottom layer uses arrays , Thread safety , Because the method has synchronized keyword , So it's thread safe .

Set disorder , Do not repeat

Set Implementation class of

1. HashSet The bottom layer uses HashMap, use HashMap in key Storing data ensures the uniqueness of data .（ disorder , Do not repeat ）
2. LinkedHashSet According to the name , The bottom layer uses linked lists and HashMap, The linked list ensures order .（ Orderly , Not to be repeated ）
3. TressSet At the bottom are red and black trees .（ Orderly , Do not repeat ）