{"A":5} is an object with field A having value 5.
No {"A":5} is a Map with key/value pair A=5.
Both can be true, but since the value before : is dynamic (changing), it the second interpretation you need.
So don't ask for JSON to be converted to a POJO (FreeCurrencyExchangeRate).
Ask for it to be converted to a Map, then iterate that map.
