How do I sort a Set to a List

Question

In Android, I have a Set , and I want to turn it into a sorted List .

How to do it with Collections.sort() ?

protected List<PackageInfo> doInBackground(Void... params) {

        Set<PackageInfo> adPackages = new HashSet<PackageInfo>();
        //ArrayList<PackageInfo> adPackages = new ArrayList<PackageInfo>();

        [..............]

        return new ArrayList<PackageInfo>(adPackages);
        //return adPackages;
    }

Answer 1

List has a constructor which allows you to create it using any Collection. Then use the Collections.sort(List list) method.

Eg

Set<String> set = new HashSet<String>();
set.add("This is a unsorted set");
List<String> list = new ArrayList<String>(set);
Collections.sort(list); // or Collections.sort(list, Comparator);

Cheers.

Answer 2

This is not really an Android question. Look for java sort, comparator . Here is a nice tutorial: http://docs.oracle.com/javase/tutorial/collections/interfaces/order.html

Answer 3

IMHO, I would use a SortedSet instead of the standard Set , and then use the addAll method of the List interface to convert the set (that is implicitly sorted) into a sorted list without having to do any sorting outside of the data structures.

Note that this will require that the objects stored within these data structures implement the Comparable interface.

Answer 4

I think this might work for you

public void sortArrayPackage(ArrayList<PackageInfo> array)
{
  Collections.sort(array, new Comparator<PackageInfo>(){
    public int compare(PackageInfo o1, PackageInfo o2) {
      System.setProperty("java.util.Arrays.useLegacyMergeSort", "true");
      String package1 = o1.packageName;
      String package2 = o2.packageName;

      return package1.compareTo(package2);
    }
  });
}