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Blog    JSON Tutorials    In Java How to Convert Map / HashMap to JSONObject? [4 Different Ways]
In Java How to Convert Map / HashMap to JSONObject? [4 Different Ways]
Last Updated on January 13th, 2019 by   App Shah   Leave a comment


 
Convert Java Map to JSONObject

Converting Objects from one form to another is a common request. There are 4 different ways to convert Java Map/HashMap to JSONObject.

We will go over details on how to convert HashMap to JSONObject in this tutorial.

Let’s get started:
Create class CrunchifyMapToJsonObject.java.

Method-1
Firstly we use Google GSON dependency to convert HashMap to JSONObject. You need below Maven dependency in your project.

<dependency>
	<groupId>com.google.code.gson</groupId>
	<artifactId>gson</artifactId>
	<version>2.8.0</version>
</dependency>
Method-2
Next we will use org.json dependency using new JSONObject().

<dependency>
	<groupId>org.json</groupId>
	<artifactId>json</artifactId>
	<version>20180130</version>
</dependency>
Method-3
Using jackson-core dependency with ObjectMapper().writeValueAsString() operation.

<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-core</artifactId>
	<version>2.9.5</version>
	<scope>compile</scope>
</dependency>
<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
	<version>2.9.5</version>
	<scope>compile</scope>
</dependency>
Method-4
Using json-simple dependency with JSONValue.toJSONString() library.

<dependency>
	<groupId>com.googlecode.json-simple</groupId>
	<artifactId>json-simple</artifactId>
	<version>1.1.1</version>
</dependency>
Make sure to add all above maven dependencies to your Java J2EE project. If you don’t have maven project then follow these steps.

Here is a complete example:
package crunchify.com.tutorial;
 
import java.util.HashMap;
import java.util.Map;
 
import org.json.JSONObject;
import org.json.simple.JSONValue;
 
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
 
/**
 * @author Crunchify.com 
 * Program: 4 Best ways to convert Java Map to JSONObject. 
 * Version: 1.0.0
 * 
 */
 
public class CrunchifyMapToJsonObject {
	public static void main(String a[]) {
 
		Map<String, String> crunchifyMap = new HashMap<String, String>();
		crunchifyMap.put("Google", "San Jose");
		crunchifyMap.put("Facebook", "Mountain View");
		crunchifyMap.put("Crunchify", "NYC");
		crunchifyMap.put("Twitter", "SFO");
		crunchifyMap.put("Microsoft", "Seattle");
		log("Raw Map ===> " + crunchifyMap);
 
		// Use this builder to construct a Gson instance when you need to set configuration options other than the default.
		GsonBuilder gsonMapBuilder = new GsonBuilder();
 
		Gson gsonObject = gsonMapBuilder.create();
 
		String JSONObject = gsonObject.toJson(crunchifyMap);
		log("\nMethod-1: Using Google GSON ==> " + JSONObject);
 
		Gson prettyGson = new GsonBuilder().setPrettyPrinting().create();
		String prettyJson = prettyGson.toJson(crunchifyMap);
 
		log("\nPretty JSONObject ==> " + prettyJson);
 
		// Construct a JSONObject from a Map.
		JSONObject crunchifyObject = new JSONObject(crunchifyMap);
		log("\nMethod-2: Using new JSONObject() ==> " + crunchifyObject);
 
		try {
			// Default constructor, which will construct the default JsonFactory as necessary, use SerializerProvider as its 
			// SerializerProvider, and BeanSerializerFactory as its SerializerFactory.
			String objectMapper = new ObjectMapper().writeValueAsString(crunchifyMap);
			log("\nMethod-3: Using ObjectMapper().writeValueAsString() ==> " + objectMapper);
		} catch (JsonProcessingException e) {
			e.printStackTrace();
		}
		
		// Convert an object to JSON text. If this object is a Map or a List, and it's also a JSONAware, JSONAware will be considered firstly.
		String jsonValue = JSONValue.toJSONString(crunchifyMap);
		log("\nMethod-4: Using JSONValue.toJSONString() ==> " + jsonValue);
 
	}
 
	private static void log(Object print) {
		System.out.println(print);
 
	}
}
Just run above Program as Java Application and you should see below output.

Raw Map ===> {Google=San Jose, Twitter=SFO, Microsoft=Seattle, Facebook=Mountain View, Crunchify=NYC}
 
Method-1: Using Google GSON ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}
 
Pretty JSONObject ==> {
  "Google": "San Jose",
  "Twitter": "SFO",
  "Microsoft": "Seattle",
  "Facebook": "Mountain View",
  "Crunchify": "NYC"
}
 
Method-2: Using new JSONObject() ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}
 
Method-3: Using ObjectMapper().writeValueAsString() ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}
 
Method-4: Using JSONValue.toJSONString() ==> {"Google":"San Jose","Twitter":"SFO","Microsoft":"Seattle","Facebook":"Mountain View","Crunchify":"NYC"}
If you know any other way to convert Java Map to JSONObject then please let us and all readers know by comment below.

Happy coding.

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About Java

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Syntax help

Variables

short x = 999; 			// -32768 to 32767
int   x = 99999; 		// -2147483648 to 2147483647
long  x = 99999999999L; // -9223372036854775808 to 9223372036854775807

float x = 1.2;
double x = 99.99d;

byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;

Loops

1. If Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
  // code
} else {
  // code
}

Example:

int i = 10;
if(i % 2 == 0) {
  System.out.println("i is even number");
} else {
  System.out.println("i is odd number");
}

2. Switch:

Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.

switch(<conditional-expression>) {    
case value1:    
 // code    
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 break;  // optional  
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 //code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.

for(Initialization; Condition; Increment/decrement){  
    //code  
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4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

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 // code 
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Classes and Objects

Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.

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class keyword is required to create a class.

Example:

class Mobile {
    public:    // access specifier which specifies that accessibility of class members 
    string name; // string variable (attribute)
    int price; // int variable (attribute)
};

How to create a Object:

Mobile m1 = new Mobile();

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        System.out.println("Hello.. Happy learning!");
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    public static void main(String[] args) {
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Collections

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Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:

Interfaces
Classes
Algorithms

This framework also defines map interfaces and several classes in addition to Collections.

Advantages:

High performance
Reduces developer's effort
Unified architecture which has common methods for all objects.

Collection	Description
Set	Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc
List	List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors
Queue	FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue.
Deque	Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail)
Map	Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc.