public class MyList {
public List<T> list;
}
var class = new MyList();
var outputString = JsonUtility.ToJson(class);
File.WriteAllText("C:\\MyFile.json", outputString);
//In reverse, you can deserialize anything doing this:
var inputString = File.ReadAllText("C:\\MyFile.json");
var class = JsonUtility.FromJson<MyList>(inputString);