Convert ArrayList<Custom> to gson in Java Android

Question

Good afternoon. I can not understand why the code does not work after publishing in the Google market. Before publishing in android studio code

ArrayList<TableAccount> tableAccount = getTableAccount();
String jsonStr = new Gson().toJson(tableAccount);

result:

Log.d(TAG, "RESULT: " + jsonStr);
RESULT: [{"name":"payment","valueFloat":0.0,"valueInt":0,"valueStr":"no"}]

But, after posting, I see:

Log.d(TAG, "RESULT: " + jsonStr);
RESULT: [{"a":"payment","b":"no","c":0,"d":0.0}]

Why do the letters a b c appear?

And where do the keys disappear? ["name", "valueFloat", "valueInt", "valueStr"]