什么时候适合使用 TrieMap？

Question

我一直在阅读一些帖子，想知道是否有人可以介绍一下 TrieMap 何时比使用 HashMap 更可取的情况。

那么本质上，什么样的架构决策应该激发 TrieMap 的使用？

Answer 1

根据文档。它是可变集合，可以安全地用于多线程应用程序。

A concurrent hash-trie or TrieMap is a concurrent thread-safe lock-free implementation of a hash array mapped trie. It is used to implement the concurrent map abstraction. It has particularly scalable concurrent insert and remove operations and is memory-efficient. It supports O(1), atomic, lock-free snapshots which are used to implement linearizable lock-free size, iterator and clear operations. The cost of evaluating the (lazy) snapshot is distributed across subsequent updates, thus making snapshot evaluation horizontally scalable.

详情见：http://lampwww.epfl.ch/~prokopec/ctries-snapshot.pdf

caching API 也非常好。因此，例如，您必须计算不同数字的阶乘，有时会重复使用此结果。

  object o {

    val factorialsCache = new TrieMap[Int, Int]()

    def factorial(num: Int) = ??? // really heavy operations
    def doWorkWithFuctorial(num: Int) = {
      val factRes = factorialsCache.getOrElseUpdate(num, {
        // we do not want to invoke it very often
        factorial(num)
           // this function will be executed only if there are no records in Map for such key
      })
      // start do some work `withfactRes`
      factRes
    }
  }

注意 - 上面的函数使用全局状态（缓存）进行写操作，但在并发线程中使用它是绝对安全的。您不会丢失任何数据。

什么时候适合使用 TrieMap？

When is it appropriate to use a TrieMap?

scala

scala-collections