文章的标题应该是：What are the Big-O Time Complexities of Java Collection Implements?
- Linda Hamilton原创
- 2024-10-28 02:33:31765浏览
Java 集合框架实现：大 O 总结
在教授“Java 速成课程”时，了解以下内容至关重要与各种集合实现相关的 Big-O 时间复杂度。虽然观众可能熟悉 Big-O 表示法，但他们不太可能知道特定集合上不同操作的具体复杂性。
幸运的是，《Java 泛型和集合》一书提供了有关这些复杂性的宝贵见解。本文总结了书中的信息，为每种类型的集合提供了详细的表格：列表、集合、映射和队列。
列表实现：
| Operation | ArrayList | LinkedList | CopyOnWriteArrayList |
|---|---|---|---|
| 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) |
集合实现：
| 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) |
| Notes | h is the table capacity |
地图实现：
| 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) |
| Notes | h is the table capacity |
队列实现：
| 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) |
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