Question

i tried using TreeSet but it disallowing doubles is there a way to change that? if there is no way, what should i use for storing (equal and not equal) elements sorted?

Answer 1

You can use a List [specifically an ArrayList] to hold the elements, and use Collections.sort() to sort it when you are done populating it.

Sometimes a PriorityQueue is also a good option – if what you actually need is to maintain the smallest/biggest element in the collection.

If you want to maintain a sorted collection – a SortedBag [from apache commons collections] might be what you are after. You can download a jar from here and add it to your classpath, and then just use it! Note that apache products are very commonly used, and thus are tested frequently!