Can Get A Specific Object Out Of List

I have a number of custom objects of type X. X has a number of parameters and must be unique in the collection. (I created my own equals method based on the custom parameters to examine this) In each object of type x, I have a list of objects y.I want to add/remove/modify easily an object y. To write the add method, it would be something like add(objTypeX, objTypeY)I would check or the collections already has a objTypeX.If so: i would add the objTypeY to the already existing objTypeX else: i would create objTypeX and add objTypeY to this object. [code] Which collections should I use? I tried with hashset but i can get a specific object out of the list, without run down the list till I find that object.