java.lang.ClassCastException: java.util.ArrayList 不能转换为 java.lang.Object[]

Question

In my android project, I want to create a generic class to store all types of entities in sharedPreferences but give the error :

java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.lang.Object[]

here is my code :

public ArrayList<E> getItems(Context context) {
        android.content.SharedPreferences settings;
        List<E> objects ;
        settings = context.getSharedPreferences(PREF_NAME,
                Context.MODE_PRIVATE);

        if (settings.contains(ITEM_NAME)) {
            String json = settings.getString(ITEM_NAME, null);
            GsonBuilder gson = new GsonBuilder();
            Type collectionType = new TypeToken<List<E>>(){}.getType();

            E[] items = gson.create().fromJson(json,
                    collectionType);  // in this line occurs error


            objects = new ArrayList<E>(Arrays.asList(items));
        } else
            return null;

        return (ArrayList<E>) objects;
    }

Answer 1

Try:

List<E> items = gson.create().fromJson(json, collectionType);

That exception is complaining that you had an ArrayList object (which was returned from fromJson() ), but you attempted to cast it to an array with that assignment to E[] items .