Iterate JSON Array Java

In order to read and write JSON data in Java, we use org.json library. The org.json library allow us to encode and decode JSON data in Java. The org.json class provide several important classes through which we can perform several operations on that JSON data. These classes are as follows:

JSONObject
JSONValue
JSONArray
JSONNumber
JSONString

These are the following steps to iterate JSON array in Java:

1) Create a Maven project and add json dependency in POM.xml file.

<!-- pom.xml -->

<dependencies>
    <!-- ... -->
    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20160810</version>
    </dependency>
    <!-- ... -->
</dependencies>

2) Create a string of JSON data which we convert into JSON object to manipulate its data.

3) After that, we get the JSON Array from the JSON Object using getJSONArray() method and store it into a variable of type JSONArray.

4) The getJSONArray() method takes array name as a string to retrieve from the Object.

5) We then use a for loop from 0 to JSONArray.length(). The length() method return the size of the array .

6) We store each index record into a JSONObject. In order to get the JSON object of a particular index, we use getJSONObject() method of JSONArray.

7) To get a value of a specified field, we use the get() method of the JSONObject by passing the field name as a string in the get() method.

JSONExample.java

// import required packages
package javaTpoint.JSONExample;

//import required classes
import org.json.JSONArray;
import org.json.JSONObject;

// create JSONExample class to iterate JSON Array
public class JSONExample{
	//main() method start
	public static void main(String args[]){    
		// create an string of JSON data
		String jsonData = "{\"locations\":[{\"lat\":\"23.053\",\"long\":\"72.629\",\"location\":\"ABC\",\"address\":\"DEF\",\"city\":\"Ahmedabad\",\"state\":\"Gujrat\",\"phonenumber\":\"1234567\"},{\"lat\":\"21.013\",\"long\":\"52.619\",\"location\":\"XYZ\",\"address\":\"MNP\",\"city\":\"Ghaziabad\",\"state\":\"UP\",\"phonenumber\":\"212321\"}]}";  
		
		// convert JSON string into JSON Object using JSONObject() method
		JSONObject json = new JSONObject(jsonData); 
		
		// get locations array from the JSON Object and store it into JSONArray
		JSONArray jsonArray = json.getJSONArray("locations");
		
		// Iterate jsonArray using for loop 
		for (int i = 0; i < jsonArray.length(); i++) {
			
			// store each object in JSONObject
		    JSONObject explrObject = jsonArray.getJSONObject(i);
		    
		    // get field value from JSONObject using get() method
		    System.out.println(explrObject.get("address"));
		}    
	}
}  

Output:

JSONExample2.java

//import package
package javaTpoint.JSONExample;

// import require classes
import java.io.FileWriter;
import java.io.IOException;

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



// create class JSONExample1
public class JSONExample1 {
	
	// main() method start
	public static void main(String[] args) {
		
		// create instance of JSONObject
		JSONObject jsonObject = new JSONObject();
		
		// use put() method for inserting the data into JSON object
		jsonObject.put("name", "Abhishek Sharma");
		jsonObject.put("department","B.E");
		jsonObject.put("branch", "C.S.E");
		jsonObject.put("year", 3);
		
		//create JSON Array and store record into JSONObject
		JSONArray list1 = new JSONArray();
		list1.add("Julia");
		list1.add("Paul");
		list1.add("Emma");

		jsonObject.put("Names", list1);
		
		JSONArray list2 = new JSONArray();
		list2.add("BCA");
		list2.add("B.Tech");
		list2.add("MCA");

		jsonObject.put("Course", list2);
		
		JSONArray list3 = new JSONArray();
		list3.add("3");
		list3.add("4");
		list3.add("2");

		jsonObject.put("Year", list3);
		
		// create instance of the FileWriter class by passing the path of the file in the constructor
		try (FileWriter file = new FileWriter("D:\\newfile.json")) {
			
			// use write() method to add JSONObject into file 
			file.write(jsonObject.toJSONString());
			file.flush();

		}
		catch (IOException e) {
			e.printStackTrace();
		}
		
		// get locations array from the JSON Object and store it into JSONArray
		JSONArray jsonArray = (JSONArray) jsonObject.get("Names");
		
		
		// Iterate jsonArray using for loop 
		for (int i = 0; i < jsonArray.size(); i++) {
			
			// get field value from JSON Array
			System.out.println(jsonArray.get(i));
		}
	}

}

Output: