Get All total value inside the child value Firebase? [closed] - firebase

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I have create school database on the firebase, I want to sum all the same keys of the one school. Like School1 have Subject key , inside Subject have students : name1, name2 , etc and each student have same subjects "AAA" , "BBB" , "CCC", now I want to sum of the subject "AAA", Can you help me how can sum of the value "AAA" keys
{
"School1": {
"Subject": {
"Name1": {
"AAA": 50,
"BBB": 60,
"CCC": 70,
"DDD": 80
},
"Name2": {
"AAA": 50,
"BBB": 60,
"CCC": 70,
"DDD": 80
},
"Name3": {
"AAA": 50,
"BBB": 60,
"CCC": 70,
"DDD": 80
}
}
},
"School2": {
"Subject": {
"Name1": {
"AAA": 50,
"BBB": 60,
"CCC": 70,
"DDD": 80
}
}
}
}
Output result of AAA:
School1:
AAA : 150

Answer 1

Here is how to go about it.
DatabaseReference aaa = FirebaseDatabase.getInstance().getReference().child("School1").child("Subject");
aaa.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
int sum = 0;
for (DataSnapshot child : dataSnapshot.getChildren()) {
sum = (int) child.child("AAA").getValue() + sum;
}
Toast.makeText(MainActivity.this, "Total Sum is "+ sum, Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});