Android : FAdd a "," in a string where in it there is this: "}{"

I'm working in a Android app and i need to put a "," between "}{" in my jsonstring before i can work with String#split(). For example i have this:

{"field1":"A","field2":"abcbab","field3":5}
    {"field1":"B","field2":"fakfef","field3":25} 
    {"field1":"A","field2":"faefe","field3":12}

how can i do that?