哈希集与树集

在哪些情况下我应该在 TreeSet 上使用 HashSet? 解决方案 HashSet 比 TreeSet 快得多(对于添加、删除和包含等大多数操作，常量时间与日志时间)但不提供排序保证，例如树集.HashSet该类为基本操作(添加、删除、包含和大小)提供恒定的时间性能.不保证元素的顺序会随着时间的推移保持不变迭代性能取决于初始容量和HashSet的负载因子.接受默认负载因子是很安全的，但您可能希望指定一个初始容量，该容量大约是您期望集增长到的大小的两倍.树集保证基本操作(添加、删除和包含)的 log(n) 时间成本保证集合的元素将被排序(升序、自然或您通过其构造函数指定的元素)(实现 SortedSet)不提供任何迭代性能调整参数提供了一些方便的方法来处理有序集合，例如 first()、last()、headSet() 和 tailSet() 等要点:两者都保证元素的无重复集合通常将元素添加到 HashSet 然后将集合转换为 TreeSet 以进行无重复排序遍历会更快.这些实现都不是同步的.也就是说，如果多个线程同时访问一个集合，并且至少有一个线程修改了该集合，则必须在外部进行同步.LinkedHashSet 在某种意义上介于 HashSet 和 TreeSet 之间.实现为一个带有链表的哈希表，但是，它提供了与 TreeSet 保证的排序遍历不同的插入顺序迭代.所以使用的选择完全取决于你的需要，但我觉得即使你需要一个有序的集合，你仍然应该更喜欢 HashSet 来创建 Set 然后将它转换为 TreeSet.例如SortedSets = new TreeSet(hashSet);I've always loved trees, that nice O(n*log(n)) and the tidiness of them. However, every software engineer I've ever known has asked me pointedly why I would use a TreeSet. From a CS background, I don't think it matters all that much which you use, and I don't care to mess around with hash functions and buckets (in the case of Java).In which cases should I use a HashSet over a TreeSet? 解决方案 HashSet is much faster than TreeSet (constant-time versus log-time for most operations like add, remove and contains) but offers no ordering guarantees like TreeSet.HashSetthe class offers constant time performance for the basic operations (add, remove, contains and size).it does not guarantee that the order of elements will remain constant over timeiteration performance depends on the initial capacity and the load factor of the HashSet.It's quite safe to accept default load factor but you may want to specify an initial capacity that's about twice the size to which you expect the set to grow.TreeSetguarantees log(n) time cost for the basic operations (add, remove and contains)guarantees that elements of set will be sorted (ascending, natural, or the one specified by you via its constructor) (implements SortedSet)doesn't offer any tuning parameters for iteration performanceoffers a few handy methods to deal with the ordered set like first(), last(), headSet(), and tailSet() etcImportant points:Both guarantee duplicate-free collection of elementsIt is generally faster to add elements to the HashSet and then convert the collection to a TreeSet for a duplicate-free sorted traversal.None of these implementations are synchronized. That is if multiple threads access a set concurrently, and at least one of the threads modifies the set, it must be synchronized externally.LinkedHashSet is in some sense intermediate between HashSet and TreeSet. Implemented as a hash table with a linked list running through it, however,it provides insertion-ordered iteration which is not same as sorted traversal guaranteed by TreeSet.So a choice of usage depends entirely on your needs but I feel that even if you need an ordered collection then you should still prefer HashSet to create the Set and then convert it into TreeSet.e.g. SortedSet<String> s = new TreeSet<String>(hashSet); 这篇关于哈希集与树集的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！