I have list of operations and each operation has a id. So how can I read it without knowing id?

The data looks like this:

I tried to write code but it doesn’t work.

myRef.child("Анна Валерьевна").child("operations").addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot snapshot) {
        String s = "";
        for (DataSnapshot ds : snapshot.getChildren()){
            if (snapshot.child("name").getValue(String.class) != null) {
                s = snapshot.child("name").getValue(String.class);
            }
            adapter.add(s);
        }
    }
    @Override
    public void onCancelled(@NonNull DatabaseError error) {
    }
});

>Solution :

Your code tries to read snapshot.child("name"), but the loop variable ds. So that should be ds.child("name").

myRef.child("Анна Валерьевна").child("operations").addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot snapshot) {
        String s = "";
        for (DataSnapshot ds : snapshot.getChildren()){
            if (ds.child("name").getValue(String.class) != null) {
                s = ds.child("name").getValue(String.class);
            }
            adapter.add(s);
        }
    }
    @Override
    public void onCancelled(@NonNull DatabaseError error) {
        throw error.toException(); // never ignore errors
    }
});