Time Complexity

Time complexity is a  way to evaluate different algorithm performance. This is a relative method, which evaluates the order of input numbers ref. to the steps to be consumed. So the best performance is independent of input numbers, i.e, n power of zero;  The worst case, the performance is a result of n square. 

Types of Time Complexity: 

the worst case, the best case, and average case. 

Assumption: 

We have infinite memory. 

No matter what kind of operations, we assume it takes one unit of time. 

List implementations:

                      get  add  contains next remove(0) iterator.remove
ArrayList             O(1) O(1) O(n)     O(1) O(n)      O(n)
LinkedList            O(n) O(1) O(n)     O(1) O(1)      O(1)
CopyOnWrite-ArrayList O(1) O(n) O(n)     O(1) O(n)      O(n)

Set implementations:

                      add      contains next     notes
HashSet               O(1)     O(1)     O(h/n)   h is the table capacity
LinkedHashSet         O(1)     O(1)     O(1) 
CopyOnWriteArraySet   O(n)     O(n)     O(1) 
EnumSet               O(1)     O(1)     O(1) 
TreeSet               O(log n) O(log n) O(log n)
ConcurrentSkipListSet O(log n) O(log n) O(1)

Map implementations:

                      get      containsKey next     Notes
HashMap               O(1)     O(1)        O(h/n)   h is the table capacity
LinkedHashMap         O(1)     O(1)        O(1) 
IdentityHashMap       O(1)     O(1)        O(h/n)   h is the table 
EnumMap               O(1)     O(1)        O(1) 
TreeMap               O(log n) O(log n)    O(log n) 
ConcurrentHashMap     O(1)     O(1)        O(h/n)   h is the table 
ConcurrentSkipListMap O(log n) O(log n)    O(1)

Queue implementations:

                      offer    peek poll     size
PriorityQueue         O(log n) O(1) O(log n) O(1)
ConcurrentLinkedQueue O(1)     O(1) O(1)     O(n)
ArrayBlockingQueue    O(1)     O(1) O(1)     O(1)
LinkedBlockingQueue   O(1)     O(1) O(1)     O(1)
PriorityBlockingQueue O(log n) O(1) O(log n) O(1)
DelayQueue            O(log n) O(1) O(log n) O(1)
LinkedList            O(1)     O(1) O(1)     O(1)
ArrayDeque            O(1)     O(1) O(1)     O(1)
LinkedBlockingDeque   O(1)     O(1) O(1)     O(1)