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Using the Gson library, how do I convert a JSON string to an ArrayList of a custom class JsonLog? Basically, JsonLog is an interface implemented by different kinds of logs made by my Android app--SMS logs, call logs, data logs--and this ArrayList is a collection of all of them. I keep getting an error in line 6.

public static void log(File destination, JsonLog log) {

    Collection<JsonLog> logs = null;

    if (destination.exists()) {

        Gson gson = new Gson();

        BufferedReader br = new BufferedReader(new FileReader(destination));

        logs = gson.fromJson(br, ArrayList<JsonLog>.class); // line 6

        // logs.add(log);

        // serialize "logs" again



It seems the compiler doesn't understand I'm referring to a typed ArrayList. What do I do?

1 Answer

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by (46k points)

You may use TypeToken to load the json string into a custom object.

logs = gson.fromJson(br, new TypeToken<List<JsonLog>>(){}.getType());

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