Java HashMultiMap存储问题

Question

I am using HashMultiMap in my code. My HashMultiMap structure is like,

Key1 -> Value11 -> Value12 -> Value13 ....

Key2 -> Value21 -> Value22 ....

Now, I want if key1 has same values (example: value11 = value12) then keep (or do not store) only one copy of the value (example: keep only value11 or do not store value12). Can anybody help me how to achieve this with an efficient (faster) way.

Answer 1

According to the HashMultiMap Javadoc, you chose the right MultiMap for that purpose:

The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an existing key-value pair has no effect.

Now, you only have to make sure that equals() (and hashCode() ) is implemented correctly on your values. I don't think you should worry about a faster way to do this. The HashMultiMap should be implemented pretty efficiently.

Answer 2

If you want this behavior why not use a structure like:

Map<Key,Set<Values>> myMap = new HashMap<Key,Set<Values>>();

EDIT:

If you want to use the HashMultiMap i would recommend the one bellow

Implementation of the MultiMap interface that uses a HashMap for the map and HashSets for automatically created sets.

http://people.csail.mit.edu/milch/blog/apidocs/common/HashMultiMap.html