Frequency of data with opensky network

Hi, I am using Open Sky live api for java, i wanted to know the frequency with which we get new data. Is it a better way to keep on listening to the server for new data, or is there a specific time interval during which new rows are inserted?
Secondly i tried using the .stream() function and it doesn't work. Any hints how to use that correctly.

I don't use Java, but the documentation for the HTTP RESTful API gives the time limitations.

Take a look at opensky-network.org/apidoc/rest.html