Merge Two JSON Arrays in Java

In this article, we will be learning how to merge two JSON arrays in Java. Let's understand step by step. First, if you are not familiar with JSON, refer JSON overview.

How to Merge Two JSON Arrays in Java?

There are multiple ways to merge two JSON arrays in Java. Some of them are:

• Using org.json library: We will use JSONArray.put() method to merge two JSON arrays.
• Using Gson library: We will use JsonArray.add() method to merge two JSON arrays.
• Using Jackson library: We will use ObjectMapper.createArrayNode() method to merge two JSON arrays.

Let's look at all of them in detail.

Using the org.json library

Let's see how to merge two JSON arrays using the org.json library. The org.json is a library that works with JSON data in Java. It provides classes and methods to create, parse, and manipulate JSON data.

Follow the steps below:

• First, we will need to add the org.json library. We can either download it from its official website or include it in our project if we are using Maven or Gradle. If you are using Maven, add this to your pom.xml file:

  <dependency>
  <groupId>org.json</groupId>
  <artifactId>json</artifactId>
  <version>20210307</version>
  </dependency>

• Next, we will create two JSON arrays.
• Then, we will merge the two JSON arrays using the JSONArray.put() method.
• Finally, we will print the merged JSON array.

Example

Below is the code demonstrating how to merge two JSON arrays using the org.json library:

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

public class MergeJsonArraysEx{
   public static void main(String[] args){
      // Create two JSON arrays
      JSONArray jsonArray1 = new JSONArray();
      jsonArray1.put(new JSONObject().put("name", "Ansh").put("age", 22));
      jsonArray1.put(new JSONObject().put("name", "John").put("age", 25));
      jsonArray1.put(new JSONObject().put("name", "Vishwa").put("age", 12));

      JSONArray jsonArray2 = new JSONArray();
      jsonArray2.put(new JSONObject().put("name", "Amit").put("age", 30));
      jsonArray2.put(new JSONObject().put("name", "Ravi").put("age", 28));
      jsonArray2.put(new JSONObject().put("name", "Sita").put("age", 20));

      // Merge the two JSON arrays
      JSONArray mergedArray = new JSONArray();
      for(int i = 0; i < jsonArray1.length(); i++){
         mergedArray.put(jsonArray1.get(i));
      }
      for(int i = 0; i < jsonArray2.length(); i++){
         mergedArray.put(jsonArray2.get(i));
      }
      // Print the merged JSON array
      System.out.println("Merged JSON Array: " + mergedArray.toString(2));
   }
}

Following is the output of the above code:

Merged JSON Array: [
  {
    "name": "Ansh",
    "age": 22
  },
  {
    "name": "John",
    "age": 25
  },
  {
    "name": "Vishwa",
    "age": 12
  },
  {
    "name": "Amit",
    "age": 30
  },
  {
    "name": "Ravi",
    "age": 28
  },
  {
    "name": "Sita",
    "age": 20
  }
]

Using Gson library

Now, let's see how to merge two JSON arrays using the Gson library. Gson is a popular library developed by Google for converting Java objects to JSON and vice versa.

To use Gson in your code, you will need to add it to your project. You can simply download it from the official website or if you are using Maven, add this to your pom.xml file:

<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.9</version>
</dependency>

Steps to follow to merge two JSON arrays using Gson:

• As discussed above, add the Gson library.
• Create two JSON arrays.
• Merge the two JSON arrays using the JsonArray.add() method.
• Print the merged JSON array.

Example

Now, let's see how to merge two JSON arrays using the Gson library:

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonElement;

import java.util.ArrayList;
import java.util.List;
import java.util.Iterator;
import java.util.Map;

public class MergeJsonArraysGsonEx{
   public static void main(String[] args){
      // Create two JSON arrays
      String jsonArray1 = "[{"name":"Ansh","age":22},{"name":"John","age":25},{"name":"Vishwa","age":12}]";
      String jsonArray2 = "[{"name":"Amit","age":30},{"name":"Ravi","age":28},{"name":"Sita","age":20}]";

      // Parse the JSON arrays
      JsonParser parser = new JsonParser();
      JsonArray array1 = parser.parse(jsonArray1).getAsJsonArray();
      JsonArray array2 = parser.parse(jsonArray2).getAsJsonArray();

      // Merge the two JSON arrays
      JsonArray mergedArray = new JsonArray();
      for(JsonElement element : array1){
         mergedArray.add(element);
      }
      for(JsonElement element : array2){
         mergedArray.add(element);
      }
      // Print the merged JSON array
      System.out.println("Merged JSON Array: " + mergedArray.toString());
   }
}

Output

Following is the output of the above code:

Merged JSON Array: [{"name":"Ansh","age":22},{"name":"John","age":25},{"name":"Vishwa","age":12},{"name":"Amit","age":30},{"name":"Ravi","age":28},{"name":"Sita","age":20}]

Using Jackson library

Now, let's see how to merge two JSON arrays using the Jackson library. Jackson is a popular library for processing JSON data in Java. It is simpler and faster than other libraries.

To use Jackson in your code, you will need to add it to your project. You can simply download it from the official website or if you are using Maven, add this to your pom.xml file:

<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.12.3</version>
</dependency>

Steps to follow to merge two JSON arrays using Jackson:

• As discussed above, add the Jackson library.
• Create two JSON arrays.
• Merge the two JSON arrays using the ObjectMapper class.
• Print the merged JSON array.

Example

Below is the code demonstrating how to merge two JSON arrays using the Jackson library:

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;


public class MergeJsonArraysJacksonEx{
   public static void main(String[] args) throws IOException{
      // Create two JSON arrays
      String jsonArray1 = "[{"name":"Ansh","age":22},{"name":"John","age":25},{"name":"Vishwa","age":12}]";
      String jsonArray2 = "[{"name":"Amit","age":30},{"name":"Ravi","age":28},{"name":"Sita","age":20}]";

      // Create ObjectMapper instance
      ObjectMapper objectMapper = new ObjectMapper();

      // Parse the JSON arrays
      JsonNode array1 = objectMapper.readTree(jsonArray1);
      JsonNode array2 = objectMapper.readTree(jsonArray2);

      // Merge the two JSON arrays
      ArrayNode mergedArray = objectMapper.createArrayNode();
      for(JsonNode element : array1){
         mergedArray.add(element);
      }
      for(JsonNode element : array2){
         mergedArray.add(element);
      }
      // Print the merged JSON array
      System.out.println("Merged JSON Array: " + mergedArray.toString());
   }
}

Output

Following is the output of the above code:

Merged JSON Array: [{"name":"Ansh","age":22},{"name":"John","age":25},{"name":"Vishwa","age":12},{"name":"Amit","age":30},{"name":"Ravi","age":28},{"name":"Sita","age":20}]