如何从高到低排序以下内容

Question

I am trying to understand how to use Collections.sort and Collections.reverse and thought that I almost had it but sometimes, my ranking is not placed in order from the highest to the lowest... I have done a series of if statements and now sure if this is the best way to go about but have some weird sorting order problem. I tried to edit my database but it is not sorting it properly....

DatabaseReference reference = FirebaseDatabase.getInstance("https://medical-review-in-australia.firebaseio.com/")
  .getReference()
  .child("Medical Clinics")
  .child("Clinics"); // getReference() is the root  // can keep adding parents

reference.addValueEventListener(new ValueEventListener() {
    @SuppressLint("SetTextI18n")
    @RequiresApi(api = Build.VERSION_CODES.N)
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        list.clear();

        popular_clinic_ranking = new ArrayList<>();


        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {

             popular_clinics = String.valueOf(snapshot.child("ranking").child("ranking").getValue());



             if (popular_clinics.equals("[Super Sleuth]")) {

                popular_clinics_name = String.valueOf(snapshot.child("Postal Information").child("name").getValue());
                popular_clinics_score = snapshot.child("Postal Information").child("total_Score").getValue(Integer.class);


               
        

             }   if (popular_clinics.equals("[Master Detective]")) {

                popular_clinics_name = String.valueOf(snapshot.child("Postal Information").child("name").getValue());
                popular_clinics_score = snapshot.child("Postal Information").child("total_Score").getValue(Integer.class);

          
          

            }   if (popular_clinics.equals("[Senior Detective]")) {

                popular_clinics_name = String.valueOf(snapshot.child("Postal Information").child("name").getValue());
                popular_clinics_score = snapshot.child("Postal Information").child("total_Score").getValue(Integer.class);


        String txt;
        txt = "Medical Clinic: " + popular_clinics_name + "\n\nTotal Score: " + popular_clinics_score + "\n\nRanking: " + popular_clinics;




            list.add(txt);
            Collections.sort(list);
            Collections.reverse(list);
            adapter.notifyDataSetChanged();  // need to use both Collections.sort and Collections.reveerse...

Now I am trying to store the information in the order of ranking and it seems to be working this way but not all the ranking are inserted into the database... Also, why is count returning 4 when I have 3 medical clinics under two parents? Is it counting one of my parents a child? Does it matter if I have capital letters or lower case when creating a child? I realised that a child has to be lowercase for it to work as a child?

 DatabaseReference reference = FirebaseDatabase.getInstance("https://medical-review-in-australia.firebaseio.com/").getReference().child("Medical Clinics").child("Clinics"); // getReference() is the root  // can keep adding parents
        reference.addValueEventListener(new ValueEventListener() {
            @SuppressLint("SetTextI18n")
            @RequiresApi(api = Build.VERSION_CODES.N)
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                list.clear();


                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {

                    popular_clinics = String.valueOf(snapshot.child("ranking").child("ranking").getValue());
                    count = (int) snapshot.getChildrenCount() - 1;
                   
                    for(int i = 0; i<= count; i++) {

                        if (popular_clinics.equals("[Super Sleuth]")) {

                            popular_clinics_name = String.valueOf(snapshot.child("Postal Information").child("name").getValue());
                            popular_clinics_score = snapshot.child("Postal Information").child("total_Score").getValue(Integer.class);


                            HashMap<String, Object> map = new HashMap<>();
                            map.put("name", popular_clinics_name);
                            map.put("score", popular_clinics_score);
                            map.put("ranking", popular_clinics);

                            FirebaseDatabase.getInstance("https://medical-review-in-australia.firebaseio.com/").getReference().child("Medical Clinics").child("Popular Clinics").child("Super Sleuth").child("super sleuth").setValue(map);


                        }

Answer 1

the problem is that you are trying to sort numeric string values. and java has a stupid problem with that so for example if you have these values in your list:

"item 01" "item 02" "item 03" "item 10"

after sorting the order will be something like this:

"item 01" "item 10" "item 02" "item 03"

So one clean way would be to store your data in a class like so maybe:

public static class People {
    String name;
    int score;
    String ranking;

    public People(String name, int score, String ranking) {
        this.name = name;
        this.score = score;
        this.ranking = ranking;
    }
}

And then make an arrayList of People like so:

ArrayList<People> peopleInfo = new ArrayList<People>();

Then add your data to this arrayList and then sort it like this:

peopleInfo.sort(Comparator.comparing(info -> info.name));

Also note that this type of sorting is case-sensitive.