Improve Java performance with MAP.
Add Contains keys Next Data Structure
HashMap O(1) O(1) O(h/n) Hash Table
EnumMap O(1) O(1) O(1) Array
LinkedHashMap O(1) O(1) O(1) Hash Table+Linked List
TreeMap O(log n) O(log n) O(log n) Red-black tree
ConcurrentSkipListMap O(log n) O(log n) O(1) Skip List
ConcurrentHashMap O(1) O(1) O(h/n) Hash table
IdentityHashMap O(1) O(1) O(h/n) Array
WeakHashMap O(1) O(1) O(h/n) Hash table
