在我的应用程序上添加备份功能，并且我正在使用realm数据库，我想将其备份到json文件。我已经创建了用于读取数据库和创建jsonobject的函数。在执行jsonobject.tostring时，我遇到了一个outofmemory错误，因为我有20多万条记录。创建json文件的任何其他方法。

RealmResults<StoneModelR> allStones = realm.where(StoneModelR.class).sort("id", Sort.ASCENDING).findAll();
for (StoneModelR singleStone : allStones) {
    try {
        JSONObject jObjectStone = new JSONObject();
        jObjectStone.put("stoneid", singleStone.id);
        jObjectStone.put("lat", singleStone.lat);
        jObjectStone.put("lng", singleStone.lon);
        jObjectStone.put("userid", singleStone.userid);
        jObjectStone.put("owner", singleStone.owner);
        jObjectStone.put("timestamp", singleStone.timestamp);
        jObjectStone.put("stonetype", singleStone.stonetype);
        jObjectStone.put("remarks", singleStone.description);
        jObjectStone.put("imported", singleStone.imported);
        jArrayStones.put(jObjectStone);
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
JSONObject stoneObj = new JSONObject();
try {
    stoneObj.put("stones", jArrayStones);
} catch (JSONException e) {
    e.printStackTrace();
}