我无法在android studio中获取firebase数据值的总和

implementation 'com.google.firebase:firebase-database:20.0.0'

FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference dataRef = database.getReference("your_data_reference");

dataRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        int sum = 0;
        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
            int value = snapshot.getValue(Integer.class);
            sum += value;
        }
        // 在这里处理总和sum的值
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        // 处理取消事件
    }
});