Conclude HashMap, TreeMap, LinkedHashMap and HashTable

	HashMap	TreeMap	LinkedHashMap	HashTable
Efficiency Get, Put, Remove, containsKey	O(1)	O(log n)	O(1)	O(1)
Iteration Order	Random	Natural sort according to key.	According to insertion.	Random
Interface	Map	Map SortedMap NavigableMap	Map	Map
Synchronized	No, but can make using Collections.synchronizedMap(obj)			Yes, Very slow, so ConcurrentHashMap
Implemetation	Buckets	RB Tree	HashTable and LinkedList using doubly LinkedList of buckets.	Buckets
	Best for random data manipulation.	Slow, but preferred for sorted data.	Preserve the order of insertion.	Obslete, use ConcurrentHashMap
Null key/value	allowed	Not-allowed, NullPointerException