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?

Community · Accepted Answer · 2017-05-23 10:30:46Z

74

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, 2017 at 10:30

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answered Oct 19, 2015 at 13:23

dguay

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7 Comments

Jacobian Over a year ago

Unfortunatelly, it seems like JSONArray from org.json.simple.* does not have length() method and getJSONObject()

dguay Over a year ago

@Jacobian Have you tried using org.json.JSONArray?

Jacobian Over a year ago

Now, I have not tried it, yet. Is it much more powerful?

dguay Over a year ago

@Jacobian I found this

rkedge Over a year ago

For org.json.simple.JSONArray you need to use the size() method (instead of length()) inherited from java.util.ArrayList.

|

RealSkeptic · Accepted Answer · 2015-10-19 13:32:09Z

52

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, 2015 at 13:32

RealSkeptic

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2 Comments

Jacobian Over a year ago

Thanks! It works. Though, it seems like I did it using java.util.Iterator

RealSkeptic Over a year ago

@Jacobian Yes, it's java.util.Iterator, but it's a raw one (E.g. a List<String> would return an Iterator<String>, 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.

yanike · Accepted Answer · 2019-12-21 06:24:26Z

40

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, 2019 at 6:24

yanike

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answered Dec 27, 2016 at 12:12

Prasad Khode

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6 Comments

Fonix Over a year ago

can achieve the same if using retrolambda with java 7

Prakhyat Over a year ago

The method forEach((<no type> item) -> {}) is undefined for the type JSONArray

Prasad Khode Over a year ago

@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

FlyingSheep Over a year ago

I beg to differ with Jugi and akcasoy. This works for me with Java 8 and org.json.JSONArray.

yanike Over a year ago

This works with org.json here -> mvnrepository.com/artifact/org.json/json Make sure you aren't using the wrong org.json

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Sivaraman · Accepted Answer · 2022-08-08 08:35:25Z

3

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

Eg:

    JSONArray myJSONArray = [...Some JSONObjects Here...];

    for (Object myObject : myJSONArray) {

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

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

edited Aug 8, 2022 at 8:35

answered Jul 11, 2021 at 17:14

Sivaraman

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