How to remove duplicate and sort objects from JSONArray using Java

Question

My JSON is:

[
   {
      "distance":32,
      "stationCode":"MIG",
      "name":"Midghat",
      "platforms":"2"
   },
   {
      "distance":32,
      "stationCode":"MIG",
      "name":"Midghat",
      "platforms":"2"
   },
   {
      "distance":69,
      "stationCode":"MDDP",
      "name":"Mandideep",
      "platforms":"2"
   },
   {
      "distance":69,
      "stationCode":"MDDP",
      "name":"Mandideep",
      "platforms":"2"
   },
   {
      "distance":18,
      "stationCode":"HBD",
      "name":"Hoshangabad",
      "platforms":"2"
   },
   {
      "distance":18,
      "stationCode":"HBD",
      "name":"Hoshangabad",
      "platforms":"2"
   },
   {
      "distance":37,
      "stationCode":"CHQ",
      "name":"Choka",
      "platforms":"2"
   },
   {
      "distance":37,
      "stationCode":"CHQ",
      "name":"Choka",
      "platforms":"2"
   },
   {
      "distance":85,
      "stationCode":"HBJ",
      "name":"Habibganj",
      "platforms":"5"
   },
   {
      "distance":85,
      "stationCode":"HBJ",
      "name":"Habibganj",
      "platforms":"5"
   },
   {
      "distance":0,
      "stationCode":"ET",
      "name":"ItarsiJn",
      "platforms":"28"
   },
   {
      "distance":8,
      "stationCode":"PRKD",
      "name":"Powerkheda",
      "platforms":"2"
   },
   {
      "distance":8,
      "stationCode":"PRKD",
      "name":"Powerkheda",
      "platforms":"2"
   },
   {
      "distance":55,
      "stationCode":"ODG",
      "name":"ObaidullaGanj",
      "platforms":"2"
   },
   {
      "distance":55,
      "stationCode":"ODG",
      "name":"ObaidullaGanj",
      "platforms":"2"
   },
   {
      "distance":44,
      "stationCode":"BKA",
      "name":"Barkhera",
      "platforms":"2"
   },
   {
      "distance":44,
      "stationCode":"BKA",
      "name":"Barkhera",
      "platforms":"2"
   },
   {
      "distance":79,
      "stationCode":"MSO",
      "name":"Misrod",
      "platforms":"2"
   },
   {
      "distance":79,
      "stationCode":"MSO",
      "name":"Misrod",
      "platforms":"2"
   },
   {
      "distance":25,
      "stationCode":"BNI",
      "name":"Budni",
      "platforms":"2"
   },
   {
      "distance":25,
      "stationCode":"BNI",
      "name":"Budni",
      "platforms":"2"
   },
   {
      "distance":91,
      "stationCode":"BPL",
      "name":"BhopalJn",
      "platforms":"6"
   },
   {
      "distance":63,
      "stationCode":"ITKL",
      "name":"ItayaKalan",
      "platforms":"2"
   },
   {
      "distance":63,
      "stationCode":"ITKL",
      "name":"ItayaKalan",
      "platforms":"2"
   }
]

I want it to sort according to distance and remove duplicate stationCode. I tried using simple if else but that process will be too much.. any shortcut for same specially for sorting.

Post the code you have tried and what are your errors :) This way it will be easier for you to learn and for us to help! — Bruno Caceiro
– Bruno Caceiro, Commented Sep 3, 2015 at 9:16

nafas · Accepted Answer · 2015-09-03 09:52:03Z

I wrote this utility a while ago, it sorts a JSONArray of JSONObjects Only condition is that your JSONobjects must contain the keys you want to sort based on (it also accept a set of keys if you want to sort based on several keys)

import java.util.Collections;
import java.util.Comparator;
import java.util.Random;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
public class JSONArraySort {
    @SuppressWarnings("unchecked")
    public static void sortASCE(JSONArray array, Object key) {
        Object[] keys = { key };
        Collections.sort(array, new JSONArrayComparator(false, keys));
    }
    @SuppressWarnings("unchecked")
    public static void sortDESC(JSONArray array, Object key) {
        Object[] keys = { key };
        Collections.sort(array, new JSONArrayComparator(true, keys));
    }
    @SuppressWarnings("unchecked")
    public static void sortASCE(JSONArray array, Object[] key) {
        Collections.sort(array, new JSONArrayComparator(false, key));
    }
    @SuppressWarnings("unchecked")
    public static void sortDESC(JSONArray array, Object[] key) {
        Collections.sort(array, new JSONArrayComparator(true, key));
    }
    private static class JSONArrayComparator implements Comparator<JSONObject> {
        private final Object[] KEYS;
        private final boolean DESC;
        public JSONArrayComparator(boolean DESC, Object[] KEYS) {
            this.KEYS = KEYS;
            this.DESC = DESC;
        }
        @Override
        public int compare(JSONObject object1, JSONObject object2) {
            int length = KEYS.length;
            for(int i = 0 ; i < length ; i++){
                String KEY = KEYS[i].toString();
                Object one = object1.get(KEY);
                Object two = object2.get(KEY);
                if(Number.class.isAssignableFrom(one.getClass()) && Number.class.isAssignableFrom(two.getClass())){
                    Double numOne = Number.class.cast(one).doubleValue();
                    Double numTwo = Number.class.cast(two).doubleValue();
                    int compared = 0;
                    if(DESC){
                        compared = numTwo.compareTo(numOne);
                    }else{
                        compared = numOne.compareTo(numTwo);
                    }
                    if(i == KEYS.length - 1 || compared != 0){
                        return compared;
                    }
                }else{
                    int compared = 0;
                    if(DESC){
                        compared = two.toString().compareTo(one.toString());
                    }else{
                        compared = one.toString().compareTo(two.toString());
                    }
                    if(i == KEYS.length - 1 || compared != 0){
                        return compared;
                    }
                }
            }
            // this shouldn't happen.
            return 0;
        }
    }
        //testing...
    public static void main(String... args) {
        JSONArray array1 = new JSONArray();
        for(int i = 0 ; i < 100 ; i++){
            Random random = new Random();
            int num1 = random.nextInt(10);
            int num2 = random.nextInt(10);
            JSONObject object = new JSONObject();
            object.put("num1", num1);
            object.put("num2", num2);
            array1.add(object);
        }
        String[] keys = { "num1", "num2" };
        sortASCE(array1, keys);
        System.out.println(array1.toString());
    }
}

now if you want to remove duplicates you can iterate through them

Set<String> stationCodes=new HashSet<String>();
JSONArray tempArray=new JSONArray();
for(int i=0;i<yourJSONArray.size();i++){
   String  stationCode=yourJSONArray.getJSONObject(i).getString("stationCode");
   if(stationsCodes.contains(stationCode){
     continue;
   }
   else{
      stationsCodes.add(stationCode);
      tempArray.add(yourJSONArray.getJSONObject(i));
   }

}


yourJSONArray= tempArray; //assign temp to original

//here how you can sort it using utility above:
JSONArraySort.sortASCE(yourJSONArray,"distance");

Thanks it worked for sorting.. filtering duplicate it did with my other logic :) Saved lots of time with this sorting thing :)
@GovindMantri, cool mate, just u know you can sort DECS with more than one keys.

Md. Kamruzzaman · Accepted Answer · 2015-09-03 09:17:31Z

1

There is no direct way to that but you can follow the way mentioned bellow:

Transform JsonObject to Java Object list using org.codehaus.jackson.map.ObjectMapper
Use a Java Map to make unique (put key = stationCode, javaObject as object)
Sort the map data based on distance.

answered Sep 3, 2015 at 9:17

Md. Kamruzzaman

1,93517 silver badges26 bronze badges

1 Comment

nafas Over a year ago

sure there is a direct way of sorting :)

KodandaRamu Kodaconti · Accepted Answer · 2018-08-08 18:28:22Z

0

Here is the code for joining '2' JSONArrays and removing duplicates from the joined JSONArray, using ArrayList<String>..contains() method:

    import java.util.ArrayList;
    import java.util.List;

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

    /**
     * @author RAM K K
     * @gmail [email protected]
     * 
     */

public class JSONOperations {

    public static void main(String[] args) {

        String s3;

        String s1 = "[{\"name\": \"Bob\", \"car\": \"Ford\"},{\"name\": \"Steve\", \"car\": \"Mercedes Benz\"},{\"name\": \"Bob\", \"car\": \"Ford\"},{\"name\": \"Bob\", \"car\": \"Ford\"},{\"name\": \"Bob\", \"car\": \"Ford\"},{\"name\": \"Bob\", \"car\": \"Ford\"},{\"name\": \"Mary\", \"car\": \"Fiat\"}]";
        String s2 = "[{\"name\": \"Mack\", \"car\": \"VW\"},{\"name\": \"Steve\", \"car\": \"Mercedes Benz\"},{\"name\": \"Bob\", \"car\": \"Ford\"}]";
        try {
            JSONArray sourceArray = new JSONArray(s2);
            JSONArray destinationArray = new JSONArray(s1);

            System.out.println(sourceArray);
            System.out.println(destinationArray);

            for (int i = 0; i < sourceArray.length(); i++) {
                destinationArray.put(sourceArray.getJSONObject(i));
            }

            System.out.println(destinationArray);
            System.out.println("JSONArray Size is: " + destinationArray.length());
            List<String> list = new ArrayList<String>();
            for (int i = 0; i < destinationArray.length(); i++) {
                if (!list.contains(destinationArray.get(i).toString())) {
                    list.add(destinationArray.get(i).toString());
                }
            }

            System.out.println("LIST: " + list);
            System.out.println("LIST Size: " + list.size());

            JSONArray distinctJSONArray = new JSONArray(list.toString());
            System.out.println(distinctJSONArray.length());
            for (int i = 0; i < distinctJSONArray.length(); i++) {
                JSONObject JSON = (JSONObject) distinctJSONArray.getJSONObject(i);
                System.out.println(JSON);
            }

            s1 = s1.substring(s1.indexOf("[") + 1, s1.lastIndexOf("]"));
            s2 = s2.substring(s2.indexOf("[") + 1, s2.lastIndexOf("]"));

            s3 = "[" + s1 + "," + s2 + "]";
            System.out.println(new JSONArray(s3));

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}

answered Aug 8, 2018 at 18:28

KodandaRamu Kodaconti

111 bronze badge

4 Comments

Radiodef Over a year ago

This doesn't do what the question asks for. "I want it to sort according to distance and remove duplicate stationCode." Also, you double-posted.

KodandaRamu Kodaconti Over a year ago

See the subject line 'How to remove duplicate and sort objects from JSONArray using Java'

Radiodef Over a year ago

That's not how the site works. The question title is just an introduction. Also, even if that was how the site works, it just reinforces my point, because your code doesn't show how to sort the list.

KodandaRamu Kodaconti Over a year ago

Yes, my code is not meant for sorting but it's for removing duplicates!

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