how to remove duplicate values in hash map?

[santhosh.R gowda]

Dear All,

How to remove duplicate values in hash map.... as we know we can apply logic and do but i want to use API methods and remove

[Christophe Verré]

If you have duplicate values, which key are you going to keep ?

[santhosh.R gowda]

If you have duplicate values, which key are you going to keep ?

The Last one as like in map when we enter duplicate keys it will keep the last duplicate key value

[Manish Singh]

What is your use case where you need to do this kind of operation

[Christophe Verré]

The Last one

Is your Map ordered ? You're using a LinkedHashMap ?

[Rob Spoor]

Check out Apache Commons Collections with its BidiMap. That's exactly what you want: a map with a one-to-one relation between keys and values instead of many-to-one.

[Istvan Kovacs]

santhosh.R gowda wrote:How to remove duplicate values in hash map.... as we know we can apply logic and do but i want to use API methods and remove

You cannot have multiple entries with the same key: calling put(someKey, someValue) and then put(someKey, someOtherValue) will overwrite the someKey - someValue pair.

To check the presence of a value, you have Map.containsValue(Object value), but it may not be efficient. You may be better off using 2 Maps, one for key - value, one for value - key pairs, or add/remove values to a (Hash)Set and call setForValues.contains(value) instead of map.containsValue(value). You may need to synchronize these operations to make sure your data is consistent at all times.

[Christophe Verré]

Check out Apache Commons Collections with its BidiMap

That's a cute name !

[Mike Simmons]

I would recommend Google Collections' BiMap instead. If only because generics have been with us for some time now, and it's annoying to deal with a library that can't handle them. And in general I find Google Collections better-engineered than most of the Apache Commons stuff I've seen. Though I haven't compared BidiMap and BiMap too carefully.