We have a bag, which has some numbers inside it. This bag has unique elements, which means every number appears once only. If we want to add 9 in a bag, then it will be not inserted as the bag already ...

You can use this collection if you are going to store data as not null keys with associate not null values, if you look internal structure of Hashtable then you will see, instance of Hashtable ...

We see the opentsdb process occasionally spinning CPU in user time, logs from querying the api/stats/threads HTTP interface show a thread resizing a HashMap at these times. We do not have a reproducer ...