Big-O Notation for Java Collections Framework Implementations
In anticipation of an upcoming Java crash-course, it is essential to provide a concise summary of the time complexity of various operations on different collection implementations.
List Implementations
| Implementation | 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
| Implementation | 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
| Implementation | 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 capacity |
| 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 capacity |
| ConcurrentSkipListMap | O(log n) | O(log n) | O(1) | - |
Queue Implementations
| Implementation | 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) |
Additional Resources
For further exploration, consider these valuable resources:
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