Foreach with JSONArray and JSONObject

Question

I'm using org.json.simple.JSONArray and org.json.simple.JSONObject. I know that these two classes JSONArray and JSONObject are incompatible, but still I want to do quite a natural thing - I want to for-each over JSONArray parsing at each iteration step one JSONObject (nested inside that JSONArray). I try to do it like so:

JSONArray arr = ...; // <-- got by some procedure
for(JSONObject o: arr){
    parse(o);
}

When I try to compile this code, indeed I get "incompatible types" error, even though it looks so natural. So, my question is what is the best way to iterate through JSONArray?

score 62 · Answer 1 · edited May 23 '17 at 10:30

62

Seems like you can't iterate through JSONArray with a for each. You can loop through your JSONArray like this:

for (int i=0; i < arr.length(); i++) {
    arr.getJSONObject(i);
}

Source

edited May 23 '17 at 10:30

Community

1
1

answered Oct 19 '15 at 13:23

dguay

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Thanks! Will check it in a second. – Jacobian Oct 19 '15 at 13:23
4

Unfortunatelly, it seems like `JSONArray` from `org.json.simple.*` does not have `length()` method and `getJSONObject()` – Jacobian Oct 19 '15 at 13:28
1

@Jacobian Have you tried using `org.json.JSONArray`? – dguay Oct 19 '15 at 13:32
1

Now, I have not tried it, yet. Is it much more powerful? – Jacobian Oct 19 '15 at 13:36
@Jacobian I've never used `org.json.simple.JSONArray` so I can't say. Maybe @RealSkeptic has better knowledge about that :) – dguay Oct 19 '15 at 13:49
1

@Jacobian [I found this](http://stackoverflow.com/questions/26936436/is-org-json-simple-jsonarray-poorly-designed) – dguay Oct 19 '15 at 13:50
3

For `org.json.simple.JSONArray` you need to use the `size()` method (instead of `length()`) inherited from java.util.ArrayList. – rkedge Sep 16 '19 at 19:32

score 46 · Accepted Answer · answered Oct 19 '15 at 13:32

46

Apparently, org.json.simple.JSONArray implements a raw Iterator. This means that each element is considered to be an Object. You can try to cast:

for(Object o: arr){
    if ( o instanceof JSONObject ) {
        parse((JSONObject)o);
    }
}

This is how things were done back in Java 1.4 and earlier.

answered Oct 19 '15 at 13:32

RealSkeptic

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Thanks! It works. Though, it seems like I did it using `java.util.Iterator` – Jacobian Oct 19 '15 at 13:35
1

@Jacobian Yes, it's `java.util.Iterator`, but it's a *raw* one (E.g. a `List` would return an `Iterator`, and then you can use `String` as the enhanced for loop variable's type. When it's raw, the base type is assumed to be `Object`. – RealSkeptic Oct 19 '15 at 13:39

score 34 · Answer 3 · edited Dec 21 '19 at 06:24

34

Make sure you are using this org.json: https://mvnrepository.com/artifact/org.json/json

if you are using Java 8 then you can use

import org.json.JSONArray;
import org.json.JSONObject;

JSONArray array = ...;

array.forEach(item -> {
    JSONObject obj = (JSONObject) item;
    parse(obj);
});

Just added a simple test to prove that it works:

Add the following dependency into your pom.xml file (To prove that it works, I have used the old jar which was there when I have posted this answer)

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20160810</version>
</dependency>

And the simple test code snippet will be:

import org.json.JSONArray;
import org.json.JSONObject;

public class Test {
    public static void main(String args[]) {
        JSONArray array = new JSONArray();

        JSONObject object = new JSONObject();
        object.put("key1", "value1");

        array.put(object);

        array.forEach(item -> {
            System.out.println(item.toString());
        });
    }
}

output:

{"key1":"value1"}

edited Dec 21 '19 at 06:24

yanike

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answered Dec 27 '16 at 12:12

Prasad Khode

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can achieve the same if using [retrolambda](http://www.vogella.com/tutorials/Retrolambda/article.html) with java 7 – Fonix Aug 25 '17 at 09:42
2

The method forEach(( item) -> {}) is undefined for the type JSONArray – Prakhyat Nov 17 '17 at 04:17
2

@Jugi the json library that I have used above is `org.json` and you can use `forEach` on `JSONArray`, you can check once if you are still in doubt – Prasad Khode Nov 13 '18 at 06:00
1

I beg to differ with Jugi and akcasoy. This works for me with Java 8 and org.json.JSONArray. – FlyingSheep May 14 '19 at 19:19
1

This works with org.json here -> https://mvnrepository.com/artifact/org.json/json Make sure you aren't using the wrong org.json – yanike Dec 20 '19 at 16:18
Also note that forEach() doesn't give you all the options a true Iterator will give. For more features, use the following: Iterator> arrayi = arrayJson.iterator(); while (arrayi.hasNext()) { JSONObject obj = (JSONObject) arrayi.next(); } – yanike Dec 20 '19 at 16:39

score 1 · Answer 4 · answered Jul 11 '21 at 17:14

Inside the for loop, you can simply typecast Object to JSONObject and access the values.

Eg:

    JSONArray myJSONArray = [...Some JSONObjects Here...];
    JSONObject myJSONObject = new JSONObject();
    for (Object myObject : myJSONArray) {

        //If you want to get JSONObject
        myJSONObject = (JSONObject) myObject;

        //If you want to access JSONObject's values
        long number     = ((JSONObject) myJSONObject).getLong("myNum");
        String myString = ((JSONObject) myJSONObject).getString("myStr");
    }

Foreach with JSONArray and JSONObject

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