Java - HashMap confusion about collision handling and the get() method

Question

I'm using a HashMap and I haven't been able to get a straight answer on how the get() method works in the case of collisions.

Let's say n > 1 objects get placed in the same key. Are they stored in a LinkedList? Are they overwritten so that only the last object placed in that key exists there anymore? Are they using some other collision method?

If they are placed in a LinkedList, is there a way to retrieve that entire list? If not, is there some other built in map for Java in which I can do this?

For my purposes, separate chaining would be ideal, as if there are collisions, I need to be able to look through the list and get information about all the objects in it. What would be the best way to do this in Java?

Thanks for all your help!

Answer 1

The documentation for Hashmap.put() clearly states, "Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced"

If you would like to have a list of objects associated with a key, then store a list as the value.

Note that 'collision' generally refers to the internal working of the HashMap, where two keys have the same hash value, not the use of the same key for two different values.