How to Combine Two JSON Arrays of Objects in Java?

Question

In Java, how can I effectively combine two JSON arrays containing objects?

JSONArray jsonArray1 = new JSONArray();
JSONArray jsonArray2 = new JSONArray();

// Sample JSON Objects
JSONObject jsonObject1 = new JSONObject();
JSONObject jsonObject2 = new JSONObject();
jsonObject1.put("name", "Alice");
jsonObject2.put("name", "Bob");

jsonArray1.put(jsonObject1);
jsonArray2.put(jsonObject2);

// Merging the arrays
JSONArray combinedArray = new JSONArray();
combinedArray.put(jsonArray1);
combinedArray.put(jsonArray2);

System.out.println(combinedArray.toString());

Answer

Combining two JSON arrays of objects in Java is a straightforward process that can be accomplished using libraries such as org.json, Jackson, or Gson. Here, we will demonstrate the use of the org.json library to merge these arrays efficiently.

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

public class JsonArrayMerger {
    public static void main(String[] args) {
        JSONArray jsonArray1 = new JSONArray();
        JSONArray jsonArray2 = new JSONArray();

        // Adding sample JSON Objects
        JSONObject jsonObject1 = new JSONObject();
        jsonObject1.put("name", "Alice");
        jsonArray1.put(jsonObject1);

        JSONObject jsonObject2 = new JSONObject();
        jsonObject2.put("name", "Bob");
        jsonArray2.put(jsonObject2);

        // Merging two JSON Arrays
        JSONArray combinedArray = new JSONArray();
        for (int i = 0; i < jsonArray1.length(); i++) {
            combinedArray.put(jsonArray1.get(i));
        }
        for (int i = 0; i < jsonArray2.length(); i++) {
            combinedArray.put(jsonArray2.get(i));
        }

        System.out.println(combinedArray.toString());
    }
}

Causes

Incorrect use of JSON handling libraries.
Not initializing JSON arrays properly.
Overlooking how JSON objects are added to arrays.

Solutions

Ensure that you have included the necessary JSON library in your project dependencies (e.g., org.json).
Create and initialize each JSON array correctly before merging.
Use methods like `put()` to add entire arrays/data correctly without losing structure.

Common Mistakes

Mistake: Forgetting to import necessary JSON classes.

Solution: Ensure to import the org.json library packages.

Mistake: Trying to merge JSON arrays without proper iteration.

Solution: Use loops to access each element of JSON arrays before adding to the new array.

Mistake: Not handling potential exceptions from JSON operations.

Solution: Wrap JSON operations inside try-catch blocks to handle potential JSONException.

Helpers

Java combine JSON arrays
merge JSON arrays in Java
JSON array manipulation Java
org.json library Java
Java JSON example