JSON Manipulation in Java – Examples

Let’s fun begin with Manipulating JSON Objects and Array with Java. If you want to learn fundamental about JSON, you can read more here.

We will use this input data for this post example: https://crunchify.com/wp-content/uploads/code/jsonArray.txt

Example 1: Complete example

package com.crunchify;

/**
 * @author Crunchify.com
 */
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.Charset;

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

public class CrunchifyJSON {

	public static void main(String[] args) {

		String jsonString = callURL("https://crunchify.com/wp-content/uploads/code/jsonArray.txt");
		System.out.println("\n\njsonString: " + jsonString);

// Replace this try catch block for all below subsequent examples
		try {  
			JSONArray jsonArray = new JSONArray(jsonString);
			System.out.println("\n\njsonArray: " + jsonArray);
		} catch (JSONException e) {
			e.printStackTrace();
		}
	}

	public static String callURL(String myURL) {
		System.out.println("Requested URL:" + myURL);
		StringBuilder sb = new StringBuilder();
		URLConnection urlConn = null;
		InputStreamReader in = null;
		try {
			URL url = new URL(myURL);
			urlConn = url.openConnection();
			if (urlConn != null)
				urlConn.setReadTimeout(60 * 1000);
			if (urlConn != null && urlConn.getInputStream() != null) {
				in = new InputStreamReader(urlConn.getInputStream(),
						Charset.defaultCharset());
				BufferedReader bufferedReader = new BufferedReader(in);
				if (bufferedReader != null) {
					int cp;
					while ((cp = bufferedReader.read()) != -1) {
						sb.append((char) cp);
					}
					bufferedReader.close();
				}
			}
		in.close();
		} catch (Exception e) {
			throw new RuntimeException("Exception while calling URL:"+ myURL, e);
		} 

		return sb.toString();
	}

}

Output:

Requested URL:https://crunchify.com/wp-content/uploads/code/jsonArray.txt

jsonString: [
	{
		color: "red",
		value: "#f00"
	},
	{
		color: "green",
		value: "#0f0"
	},
	{
		color: "blue",
		value: "#00f"
	},
	{
		color: "cyan",
		value: "#0ff"
	},
	{
		color: "magenta",
		value: "#f0f"
	},
	{
		color: "yellow",
		value: "#ff0"
	},
	{
		color: "black",
		value: "#000"
	}
]

jsonArray: [{"color":"red","value":"#f00"},{"color":"green","value":"#0f0"},{"color":"blue","value":"#00f"},{"color":"cyan","value":"#0ff"},{"color":"magenta","value":"#f0f"},{"color":"yellow","value":"#ff0"},{"color":"black","value":"#000"}]

Another must read: How to Merge/Concat Multiple JSONObjects in Java? Best way to Combine two JSONObjects

Example 2: Iterate through JSONArray and display each JSONObjects

		try {
			JSONArray jsonArray = new JSONArray(jsonString);

			int count = jsonArray.length(); // get totalCount of all jsonObjects
			for(int i=0 ; i< count; i++){   // iterate through jsonArray 
				JSONObject jsonObject = jsonArray.getJSONObject(i);  // get jsonObject @ i position 
				System.out.println("jsonObject " + i + ": " + jsonObject);
			}
		} catch (JSONException e) {
			e.printStackTrace();
		}

Output:

jsonObject 0: {"color":"red","value":"#f00"}
jsonObject 1: {"color":"green","value":"#0f0"}
jsonObject 2: {"color":"blue","value":"#00f"}
jsonObject 3: {"color":"cyan","value":"#0ff"}
jsonObject 4: {"color":"magenta","value":"#f0f"}
jsonObject 5: {"color":"yellow","value":"#ff0"}
jsonObject 6: {"color":"black","value":"#000"}

Example 3: How to add JSONObject to JSONArray?

		try {
		    JSONArray jsonArray = new JSONArray(jsonString);

		    JSONObject jsonObj= new JSONObject();  // these 4 files add jsonObject to jsonArray
		    jsonObj.put("color", "CrunchifyColor1");
		    jsonObj.put("value", "#111");
		    jsonArray.put(jsonObj);

			int count = jsonArray.length(); // get totalCount of all jsonObjects
			for(int i=0 ; i< count; i++){   // iterate through jsonArray 
				JSONObject jsonObject = jsonArray.getJSONObject(i);  // get jsonObject @ i position 
				System.out.println("jsonObject " + i + ": " + jsonObject);
			}

		} catch (JSONException e) {
			e.printStackTrace();
		}

Output:

jsonObject 0: {"color":"red","value":"#f00"}
jsonObject 1: {"color":"green","value":"#0f0"}
jsonObject 2: {"color":"blue","value":"#00f"}
jsonObject 3: {"color":"cyan","value":"#0ff"}
jsonObject 4: {"color":"magenta","value":"#f0f"}
jsonObject 5: {"color":"yellow","value":"#ff0"}
jsonObject 6: {"color":"black","value":"#000"}
jsonObject 7: {"color":"CrunchifyColor1","value":"#111"}

In next post I’ll add some more complex examples.

Please do let me know if you have any suggestions or any query on JSON in comment section. I’ll try to resolve it.