A java.util.List is always ordered (it retains elements in whatever order you put them in), but it isn't necessarily sorted. You can sort the elements after you're done inserting them using Collections.sort(). Or you can replace the List with a TreeSet, which will sort the elements as they are added. Note that both Collections.sort() and TreeSet can work with either Comparable or Comparator objects - consult the docs to see how.
The difference between the two approaches being that a TreeSet will eliminate duplicates.
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus