How do the Big-O complexities of different Java Collections Framework implementations impact performance and guide data structure selection?

Big-O Notation for Java Collections Framework Implementations

Understanding the Big-O order of operations for various Java Collections Framework implementations is crucial when selecting the appropriate data structure for a specific task.

List Implementations

• ArrayList: O(1) for get, add, contains, and iterator.remove; O(n) for remove(0)
• LinkedList: O(n) for get, O(1) for add, contains, and remove(0), O(1) for iterator.remove
• CopyOnWriteArrayList: O(1) for get, O(n) for add, contains, and remove(0), O(n) for iterator.remove

Set Implementations

• HashSet: O(1) for add and contains, O(h/n) for next (where h is the table capacity)
• LinkedHashSet: O(1) for all operations
• CopyOnWriteArraySet: O(n) for add and contains, O(1) for next
• EnumSet: O(1) for all operations
• TreeSet: O(log n) for all operations
• ConcurrentSkipListSet: O(log n) for all operations

Map Implementations

• HashMap: O(1) for get and containsKey, O(h/n) for next (where h is the table capacity)
• LinkedHashMap: O(1) for all operations
• IdentityHashMap: O(1) for get and containsKey, O(h/n) for next (where h is the table capacity)
• EnumMap: O(1) for all operations
• TreeMap: O(log n) for all operations
• ConcurrentHashMap: O(1) for get and containsKey, O(h/n) for next (where h is the table capacity)
• ConcurrentSkipListMap: O(log n) for all operations

Queue Implementations

• PriorityQueue: O(log n) for offer and poll, O(1) for peek and size
• ConcurrentLinkedQueue: O(1) for all operations
• ArrayBlockingQueue: O(1) for offer, peek, and poll, O(1) for size
• LinkedBlockingQueue: O(1) for offer, peek, and poll, O(1) for size
• PriorityBlockingQueue: O(log n) for offer and poll, O(1) for peek and size
• DelayQueue: O(log n) for offer and poll, O(1) for peek and size
• LinkedList: O(1) for all operations
• ArrayDeque: O(1) for all operations
• LinkedBlockingDeque: O(1) for all operations

Additional Resources

For a comprehensive summary table and annotated outline of all Java Collections Framework implementations, refer to the following resources:

• Collections Overview: https://docs.oracle.com/javase/tutorial/collections/intro/index.html
• Annotated Outline: https://docs.oracle.com/javase/7/docs/api/java/util/package-summary.html

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