How to remove multiple children in one call - Realtime Firebase

Java doesn't support template literals with the $i notation in regular strings, as far as I know. The simplest way to build a map with the null values:

Map<String, Object> updates = new HashMap<>();
for(i in removedProductVariationIdList){
    updates.put("user"+i, null);
}

Also see:

• Firebase Transactions of Add, Delete on Multiple Nodes

You need to declare values as a map.

val map = mutableMapOf<String, Any?>()

Solution:

With the help from Frank's reference link and danartillaga answers, below is my code in Kotlin which works:

val productVariationRef = FirebaseDatabase.getInstance().getReference("Product_Variation")
val updates = hashMapOf<String, Any?>()
for (i in removedProductVariationIdList){
   updates.put("/$i", null)
}
productVariationRef.updateChildren(updates)

Firebase Structure - It will delete all the key (e.g. 3, 4, 5, 8) stored in removedProductVariationIdList together with its children, whole branch dissapears, which is exactly what i want :