Is there a way, I can empty the whole JSONObject -- java

Question

I have to populate a json object like this, let say it is named detailJSON:

{"amount": "5.00", "ac_no": "123456" } 

I do it this way:

detailJSON.put("amount","5.00");
detailJSON.put("ac_no","123456");

After this, the detail is entered in some shared preferences, and now I want to clear this JSONObject and use the same detailJSON object to store another json (with different keys), this way:

{"amount":"6.00", "loan_no":"123456"}

I know there is a method, remove(), that removes the particular key and corresponding value.

This works:

detailJSON.remove("amount");
detailJSON.remove("ac_no");

and then use it --

detailJSON.put("amount","6.0");
detailJSON.put("loan_no","123456");

Now this is a very simple example. In the code I'm working on, I have a lot of keys, so using remove actually increases the LOC. Also, each time before removing I need to check whether JSONObject has that particular key or not.

Is there any other way, I can implement clearing of the JSONObject??

I tried

detailJSON=null ;
detailJSON=new JSONObject();

But it does not work.

I am basically in search of something like clear() method, if exists.

Answer 1

You could, but it will be a hack.

Iterator i = detailJSON.keys();
while(i.hasNext()) {
    i.next().remove();
}

//or

detailJSON.keySet().clear();

It works, because JSONObject.keySet() will return you this.map.keySet(). And what JavaDoc for HashMap.keySet() said:

Returns a Set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

Java's HashMap from collections will return you java.util.HashMap.KeySet and java.util.HashMap.KeySet.clear(); just calls map.clear() (KeySet is an inner class of java.util.HashMap)

Answer 2

Iterator keys = detailJSON.keys();
while(keys.hasNext())
  detailJSON.remove((String)detailJSON.keys().next());

Answer 3

this version has an overhead because of getting the key-set everytime, but it works without concurrent modification exception.

while(json.length()>0)
   json.remove(json.keys().next());