Java Collections Framework: A Comprehensive Guide to Big-O Implementations
In the Java Collections Framework, each collection has its distinct performance characteristics determined by its underlying data structure. Understanding the Big-O complexities of these operations can guide effective selection and optimization of data structures.
List Implementations
Operation | ArrayList | LinkedList | CopyOnWrite-ArrayList |
---|---|---|---|
get | O(1) | O(n) | O(1) |
add | O(1) | O(1) | O(n) |
contains | O(n) | O(n) | O(n) |
next | O(1) | O(1) | O(1) |
remove(0) | O(n) | O(1) | O(n) |
iterator.remove | O(n) | O(1) | O(n) |
Set Implementations
Operation | HashSet | LinkedHashSet | CopyOnWriteArraySet | EnumSet | TreeSet | ConcurrentSkipListSet |
---|---|---|---|---|---|---|
add | O(1) | O(1) | O(n) | O(1) | O(log n) | O(log n) |
contains | O(1) | O(1) | O(n) | O(1) | O(log n) | O(log n) |
next | O(h/n) | O(1) | O(1) | O(1) | O(log n) | O(1) |
Map Implementations
Operation | HashMap | LinkedHashMap | IdentityHashMap | EnumMap | TreeMap | ConcurrentHashMap | ConcurrentSkipListMap |
---|---|---|---|---|---|---|---|
get | O(1) | O(1) | O(1) | O(1) | O(log n) | O(1) | O(log n) |
containsKey | O(1) | O(1) | O(1) | O(1) | O(log n) | O(1) | O(log n) |
next | O(h/n) | O(1) | O(h/n) | O(1) | O(log n) | O(h/n) | O(1) |
Queue Implementations
Operation | PriorityQueue | ConcurrentLinkedQueue | ArrayBlockingQueue | LinkedBlockingQueue | PriorityBlockingQueue | DelayQueue | LinkedList | ArrayDeque | LinkedBlockingDeque |
---|---|---|---|---|---|---|---|---|---|
offer | O(log n) | O(1) | O(1) | O(1) | O(log n) | O(log n) | O(1) | O(1) | O(1) |
peek | O(1) | O(1) | O(1) | O(1) | O(1) | O(1) | O(1) | O(1) | O(1) |
poll | O(log n) | O(1) | O(1) | O(1) | O(log n) | O(log n) | O(1) | O(1) | O(1) |
size | O(1) | O(n) | O(1) | O(1) | O(1) | O(1) | O(1) | O(1) | O(1) |
Additional Resources
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