i fed a list of .mp3 streaming sources that i use daily with b4a to the b4j mediaplayer. all connected without issue, but almost all disconnected within a second or two. the ones that did not connect streamed fine. so, there seems to be an issue with mediaplayer under b4j. i tried both W7 and W10 and jdk 8.xxx. i should mention that, occasionally, some streams which disconnected were able to stream if i kept starting the app over and over.
i had better luck with a webview. you get a nice little "radio view", and the streams which disconnected via mediaplayer, streamed fine with webview's html5 features (ie, <audio>). note: if you go this way, don't be surprised if you have to manually click on the play icon. google has turned off the autoplay feature. you can add the autoplay attribute, but it may not work. i had no cases of disconnect with the webview.
a final comment, you're not going to write a better streaming app than vlc yourself. you can run vlc through your b4j app via sh. sometimes you have to go with the flow.