My app loads items from a list that contains categories and other items

The list is like this with the names of repeated categories

What I want to do is load only the category names without repeating an existing name

Example: TV Shows, Space, Nature, Cars

My Cod:

        DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Data");
        Query query = databaseReference.orderByChild("category");
        query.addValueEventListener(new ValueEventListener() {
            @SuppressLint("NotifyDataSetChanged")
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
               // dataList.clear();
                for (DataSnapshot dataSnapshot : snapshot.getChildren()) {
                    ModelCatMenu dataClass = dataSnapshot.getValue(ModelCatMenu.class);
                    dataList.add(dataClass);
                }

                adapter.notifyDataSetChanged();
            }

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

            }
        });

Data:

{
  "Data": {
    "Abstract": {
      "-Nw0kYmCYjEApQYc_iew": {
        "category": "Abstract",
        "imageLink": "https://link",
        "name": "name"
      }
    },
    "Filme": {
      "-NvyyIvCLDveuyUHP0I4": {
        "category": "Filme",
        "imageLink": "https://link",
        "name": "Cong"
      },
      "-NvyyP8qn9IhDJVoNcEk": {
        "category": "Filme",
        "imageLink": "https://link",
        "name": "name"
      }
    },
    "Tv Shows": {
      "-Nw0kkdorKFS0oi2N3gj": {
        "category": "Tv Shows",
        "imageLink": "https://link",
        "name": "name"
      }
    }
  }
}

I tried this but without success, something is missing

List<String> uniqueCategories = new ArrayList<>();

query.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
            Category category = snapshot.getValue(Category.class);
            String categoryName = category.getCategory();

            if (!uniqueCategories.contains(categoryName)) {
                uniqueCategories.add(categoryName);
            }

        }
     adapter.notifyDataSetChanged();
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        // Trate o erro, se necessário
    }
});