Generify JSONObject string keys

Question

I have existing code which use org.json.JSONObject's Iterator

JSONObject obj = new JSONObject();
obj.put("key1", "value1");
obj.put("key2", "value2");
Iterator keys = obj.keys();
...

With compile warning

Iterator is a raw type. References to generic type Iterator<E> should be parameterized

I can update to generic version:

Iterator<?> keys = obj.keys();

But isn't there a way to "generify" JSONObject with String keys?

I find this answer but its suggestion doesn't compiled

JSONObject<String,Object> obj=new JSONObject<String,Object>();

EDIT

Using Iterator<String> keys = obj.keys(); I'm getting a type safety warning:

Type safety: The expression of type Iterator needs unchecked conversion to conform to Iterator<String>

Also using Eclipse Infer generics doesn't execute any code changes

Are you using org.json.JSONObject or org.json.simple.JSONObject? — D.B.
– D.B., Commented Dec 23, 2018 at 8:31

D.B. · Accepted Answer · 2018-12-23 08:39:04Z

1

The answer you provided a link to is using a different class than the one you are using. If you look at the source for org.json.JSONObject you'll find the following:

public Iterator<String> keys() {
    return this.keySet().iterator();
}

Which means you can write the following code:

    JSONObject obj = new JSONObject();
    obj.put("key1", "value1");
    obj.put("key2", "value2");
    Iterator<String> keys = obj.keys();

    while(keys.hasNext()){
        System.out.println(keys.next());
    }

and it will generate the following output:

key1
key2

answered Dec 23, 2018 at 8:39

D.B.

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4 Comments

Ori Marko Over a year ago

But then I get a warning Type safety: The expression of type Iterator needs unchecked conversion to conform to Iterator<String>

D.B. Over a year ago

I'm using the latest version - org.json:json:20180813 and I don't get any such warning. Please provide more details about your setup.

Ori Marko Over a year ago

This is a warning in Eclipse, basically you cast to String although it's not safe, you don't define JSONObject with String keys. BTW did you downvote?

howlger Over a year ago

@user7294900 JSONObject has hardcoded String keys. The code given in the answer should not cause such a warning. Generics are used since version 2014-05-03. Please upgrade your JSON-java dependency.

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