java - How to use Firebase's ServerValue.TIMESTAMP as a child and set a value to it

Question

I want to create a structure like

"child1/1510612788766/": key: "quantity", value: 10
"child1/1510612788767/": key: "quantity", value: 4
"child1/1510612788768/": key: "quantity", value: 1
"child2/1510612788710/": key: "quantity", value: 6
"child2/1510612788756/": key: "quantity", value: 8

but when I try:

ref.child("child1").child(ServerValue.TIMESTAMP);

there is a compilation error on the second child call:

Error:(59, 52) error: incompatible types: Map<String,String> cannot be converted to String

I know that this error is because the method expects a Map<String, Object> map instead of Map of timestamp.

But how could I store the ServerValue this way and set a value to it?

Answer 1

Waitting for answers