やるたびにググってる
毎度迷子になるの面倒
StringなJsonからList
String somethingsJson = "";
Gson gson = new Gson();
Type collectionType = new TypeToken<Collection<Something>>(){}.getType();
List<Something> somethings = gson.fromJson(somethingsJson, collectionType);
ListからStringなJson
Gson gson = new Gson();
List<Something> somethings = new ArrayList<>();
String somethingsJson = gson.toJson(somethings);