Question

I have an arraylist of several items. An item may have a specific int field LYING equal to OFF, FLOOR, RB1, RB2, RB3 or RB4.

For example OFF is defined as:

public static final int OFF = 0;

Regarding some specific global variables I would like to order those elements in a custom way, that may be for example:

• all the RB1 items at the begin of the arraylist, all the RB2 items after any RB3 items (regardless the OFF items) and all the RB4 at the end of the arraylist.

Which is the best solution for my case?

Focusing on writing some custom:

public int compare(Object o1, Object o2) {
    if(globalVariable0 > 0) {
        if(o1.getLying() == o2.getLying)
            return 0;
        if(o1.getLying() == RB1 && o2.getLying != RB1)
            return -1;
        ...
    }else{
        ...
    }

or..?

Answer 1

There are probably several solutions for this but since we are talking about an “unnatural” order I’d hold an object with the correct order, for example a map that I can query for sortposition in my compare method, then the sortorder could be easy to edit in a properties-file maybe. Perhaps like this:

public int compare(Object o1, Object o1){
  ActualType a1 = (ActualType) o1;
  ActualType a2 = (ActualType) o2;
  SortedOrderMap map = getSortOrderMap(); //cached of course
  Integer l1 = map.get(a1.getLying());
  Integer l2 = map.get(a2.getLying());
  return l1.compareTo(l2);
}