Cannot properly sort through my arraylist

Question

so I'm trying to sort my arraylist of geometric objects in ascending order (by area). However, I'm running into an error

The method add(GeometricObject) in the type ArrayList<GeometricObject> is not applicable for the arguments (double)

in my code block

private static void selectionSort(ArrayList<GeometricObject> list) {
        for (int i = 0; i < list.size(); i++) {
            if (i < list.size() - 1) {
                if (list.get(i).getArea() > list.get(i + 1).getArea()) {
                    double j = list.get(i).getArea();
                    list.remove(i);
                    list.add(i, list.get(i));
                    list.remove(i + 1);
                    list.add(j).getArea();
                    i = -1;
                }
            }
        }

     }

line

list.add(j).getArea();

Again, I'm just trying to sort them in order of their areas so i can later print the array. Any help or pointers in the right direction would be appreciated, thanks!

Why are you adding a double to a ArrayList<GeometricObject>? — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Oct 14, 2015 at 0:33
what exactly is the purpose of these lines: list.add(i, list.get(i)); and list.add(j).getArea();? doesn't make a lot of sense to me — user4668606
– user4668606, Commented Oct 14, 2015 at 0:36
Ahh I didn't even catch myself facepalm. I think i may have solved the error by setting j equal to a GeometricObject and removing the getArea method and doing the same for the list.add(j) line. @SotiriosDelimanolis — RiFF RAFF
– RiFF RAFF, Commented Oct 14, 2015 at 0:37
Doesn't really make sense to me either lol, I thought i was just swapping around the areas when in reality I'm supposed to be swapping the entire objects list order. @Paul — RiFF RAFF
– RiFF RAFF, Commented Oct 14, 2015 at 0:38
Why don't you want to sort by using standard java Collections.sort and Comparator? — rsutormin
– rsutormin, Commented Oct 14, 2015 at 0:45

Marquis Blount · Accepted Answer · 2015-10-14 00:43:33Z

1

I think you wanted to do this instead

private static void selectionSort(ArrayList<GeometricObject> list) {
        for (int i = 0; i < list.size(); i++) {
            if (i < list.size() - 1) {
                if (list.get(i).getArea() > list.get(i + 1).getArea()) {
                    GeometricObject j = list.get(i);
                    list.remove(i);
                    list.add(i, list.get(i));
                    list.remove(i + 1);
                    list.add(j);
                    i = -1;
                }
            }
        }

     }

I would consider change j to a more meaningful name. The issue occurred because of incomparable datatypes

edited Oct 14, 2015 at 0:43

answered Oct 14, 2015 at 0:42

Marquis Blount

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2 Comments

RiFF RAFF Over a year ago

This is exactly what i was aiming for. Thanks!

Dinesh Over a year ago

@RiFFRAFF you can make use of Collections.Sort() method to sort your ArrayList with Geometric objects rather than coding down selection sort and merge sort on your own. I have posted it here ! stackoverflow.com/questions/33116198/…

Al2O3 · Accepted Answer · 2015-10-16 09:36:45Z

0

Try this:

    Collections.sort(list, new Comparator<GeometricObject>() {
        @Override
        public int compare(GeometricObject o1, GeometricObject o2) {
            if (o1.getGmtModified() != null && o2.getGmtModified() != null){
                if(o1. getArea() < o2. getArea()) {
                    return 1;
                }else if(o1. getArea() > o2. getArea()){
                    return -1;
                }else{
                    return 0;                        
                }
            }
            return 0;
        }
    });

answered Oct 16, 2015 at 9:36

Al2O3

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