How can i have a HashMap in Java with duplicate keys?

Question

I need a collection in Java that is going to store a pair, a key and a value.

So I decided to use a HashMap<String,String>, but I noticed that when I try to add a key that already exists, the previous (key,value) is replaced by the new one (NewKey,NewValue) and the previous entry is lost. So when I have duplicate keys, the previous key is replaced by the new one.

How can I have a HashMap with duplicate keys?

What would you expect to get back when you retrieved by a key? — Ted Hopp, Sep 23 '13 at 20:44
the question is, what you doing that you need that behavior? you may use a Map> — BlaShadow, Sep 23 '13 at 20:46
I need to store a pair of a key and a value, but i would like to have duplicate keys — programmer, Sep 23 '13 at 20:47
this may help you http://stackoverflow.com/questions/1062960/map-implementation-with-duplicate-keys — BlaShadow, Sep 23 '13 at 20:48

Eugen Halca · Accepted Answer · 2017-04-10T16:43:10.277

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you need MultiMap, take a look at Google Guava Multimap

edited Apr 10 '17 at 16:43

answered Sep 23 '13 at 20:46

Eugen Halca

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the link above is broken. – AADProgramming Mar 26 '17 at 10:06
i've updated link – Eugen Halca Apr 10 '17 at 16:44

score 2 · Answer 2 · edited Jul 12 '20 at 13:57

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If you want to map a key to a collection of values, take a look at Guava's Multimap. If you don't want to use a third-party library, you can simulate a Multimap with a Map<String, Collection<String>>. The Java tutorial on the Map interface has an example of implementing a Multimap.

edited Jul 12 '20 at 13:57

drac_o

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answered Sep 23 '13 at 20:46

Ted Hopp

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How can i have a HashMap in Java with duplicate keys?

2 Answers2

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