How to avoid duplicate data in listview firebase

Question

I know this question was already asked and I followed this Question.

My Firebase structure.

I need to display expensesName in listview. If data is repeated more than once it should display the data in listview for one time only, there is no duplicates of data and if there is no duplication data in firebase, it should also be visible in listview.

I have tried the code below to get away the duplicate data but it doesn't work for data which is not repeated in firebase.

For Example in my firebase

oil // repeated 2 times
petrol //repeated 1 time

I need ouput as

oil
petrol

but actual output am getting is

oil

MainActivity

 listfirebaseref=FirebaseDatabase.getInstance().getReference("Expenses Details").child(username).child(monthYr);

listfirebaseref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            expenseClassList.clear();
            int sum = 0;
            ExpenseClass expenseClass;
            Log.d("Tag", "on list Adpter");
            for (DataSnapshot ds : dataSnapshot.getChildren()) {
                for (DataSnapshot data : ds.getChildren()) {
                    String exp = data.child("expensesName").getValue(String.class);
                    spacecraft = new ExpensesName(exp);
                    expenseClassList.add(spacecraft);
                    Log.d("Tag", " " + expenseClassList);
                    }
                    }
                    for (int i = 0; i < expenseClassList.size(); i++) {
                        for (int j = 0; j < expenseClassList.size(); j++) {
                            if ((expenseClassList.get(i).equals(expenseClassList.get(j)))) {
                                expenseClassList.remove(j);
                                //j;
                            }
                            }
                            }
                            Log.d("Tag", " list Adpter");
                            adapter.notifyDataSetChanged();
        }



        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });

Ihor Bykov · Accepted Answer · 2018-10-10T18:46:15.797

0

Why not use HashSet instead of ArrayList?

Btw it's strange that you didn't get concurrent modification exception. You can't remove from the list while iterating it. Link

Set<ExpensesName> expenseClassList = new HashSet<>();

   ....

   for (DataSnapshot ds : dataSnapshot.getChildren()) {
                for (DataSnapshot data : ds.getChildren()) { 
                  String exp = data.child("expensesName").getValue(String.class);
                    spacecraft = new ExpensesName(exp);
                    expenseClassList.add(spacecraft);
                }
   }

Here your expenseClassList will contains only unique strings

edited Oct 10 '18 at 18:46

answered Oct 10 '18 at 16:03

Ihor Bykov

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Can you give some snippet to get through it.i really dnt know how to get my expected output.please help.me out – Padma Priya Oct 10 '18 at 16:11
@PadmaPriya sure – Ihor Bykov Oct 10 '18 at 18:12
Thank-you..I will try it and will say the result and I sorry to ask this simple doubt but I really don't know about hashmap.in the above code you have used `set=new hashmap<>()` here we have to use `set` or datamodel class name `set` – Padma Priya Oct 10 '18 at 18:26
@PadmaPriya In the above code, I used only HashSet. – Ihor Bykov Oct 10 '18 at 18:28
@PadmaPriya HashSet is a collection that store only unique items – Ihor Bykov Oct 10 '18 at 18:29
Ya i can understand sir. I have to use `set` name of datamodel class instead of `set` – Padma Priya Oct 10 '18 at 18:44
@PadmaPriya Yes, you are right: `Set expenseClassList = new HashSet<>()` – Ihor Bykov Oct 10 '18 at 18:45
Thankyou sir. I will try the code and let you know.thank you for your help sir – Padma Priya Oct 10 '18 at 18:48

score -1 · Answer 2 · answered Oct 10 '18 at 17:24

use the HashSet instead of ArrayList

    HashSet<String> expenseClassList = new HashSet<>();

     public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        expenseClassList.clear();
        int sum = 0;
        ExpenseClass expenseClass;
        Log.d("Tag", "on list Adpter");
        for (DataSnapshot ds : dataSnapshot.getChildren()) {
            for (DataSnapshot data : ds.getChildren()) {
                if(!expenseClassList.contains(data.child("expensesName").getValue(String.class)){
                       expenseClassList.add(spacecraft);
                    }                    
                }
                        Log.d("Tag", " list Adpter");
                        adapter.notifyDataSetChanged();
    }

How to avoid duplicate data in listview firebase

2 Answers2