This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
You could ofcourse use List<Object> but that would not be really type-safe. If the things you want to store are always triplets of Long, Float and String, then when you use a List<Object> the compiler will not be able to check that for you, and you might inadvertently put an Object into the list that contains something else than a Long, Float and String.