使用 HashMultiset 获取值的 Multimap

发布于 2024-08-19 01:16:12 字数 767 浏览 8 评论 0 原文

我试图拥有一个（基于哈希的）多重映射，其中每个键都有一个（基于哈希的）值的多重集。请参阅示例：

Multimap<Object, Object> mmap = Multimaps.newMultimap(
    Maps.<Object, Collection<Object>>newHashMap(), 
    new Supplier<Collection<Object>>() {
  public Collection<Object> get() {
    return HashMultiset.create();
  }
});
mmap.put("1", "2");

但是，

System.out.println(mmap.get("1") instanceof Multiset<?>); 
//false, the returned collection is not a HashMultiset,
//but a (private) WrappedCollection

看来我无法访问我创建的多重集？我希望能够将其作为 Multiset（包装在 Multisets.unmodifyingMultiset() 中）返回。我也不想每次都将其复制到新的 Multiset 中。除了切换回 Map> 并在代码中添加 Multimap 想要消除的复杂性之外，我还有其他选择吗？

原文

I'm trying to have a (hash-based) Multimap with a (hash-based) Multiset of values for each key. See the example:

Multimap<Object, Object> mmap = Multimaps.newMultimap(
    Maps.<Object, Collection<Object>>newHashMap(), 
    new Supplier<Collection<Object>>() {
  public Collection<Object> get() {
    return HashMultiset.create();
  }
});
mmap.put("1", "2");

But then,

System.out.println(mmap.get("1") instanceof Multiset<?>); 
//false, the returned collection is not a HashMultiset,
//but a (private) WrappedCollection

So it seems I cannot access the multiset I created? I wanted to be able to return that, as a Multiset (wrapped in Multisets.unmodifiableMultiset()). I don't want to copy it into a new Multiset each time either. Do I have any other option than switching back to Map<K, Multiset<V>> and adding in my code the complexity that Multimap meant to eliminate?