Convert Map to JSON in Java

Convert Map to JSON in Java.

This example shows how to convert a Map to JSON object in Java.

Google Gson library is used to convert HashMap to JSON Object and JSON String back to the Map object in Java.

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

public class MapToJson {

    public static void main(String[] args) {
        Map<string, string=""> colours = new HashMap<string, string="">();
        colours.put("BLACK", "#000000");
        colours.put("RED", "#FF0000");
        colours.put("GREEN", "#008000");
        colours.put("BLUE", "#0000FF");
        colours.put("YELLOW", "#FFFF00");
        colours.put("WHITE", "#FFFFFF");

        //
        // Convert a Map into JSON string.
        //
        Gson gson = new Gson();
        String json = gson.toJson(colours);
        System.out.println("json = " + json);

        //
        // Convert JSON string back to Map.
        //
        Type type = new TypeToken<map<string, string="">>() {}.getType();
        Map <string, string=""> map = gson.fromJson(json, type);
        for (String key: map.keySet()) {
            System.out.println("map.get = " + map.get(key));
        }
    }

}</string,></map<string,></string,></string,>

import com.google.gson.Gson;

import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;

import java.util.HashMap;

import java.util.Map;

public class MapToJson {

public static void main(String[] args) {

Map<string, string=""> colours = new HashMap<string, string="">();

colours.put("BLACK", "#000000");

colours.put("RED", "#FF0000");

colours.put("GREEN", "#008000");

colours.put("BLUE", "#0000FF");

colours.put("YELLOW", "#FFFF00");

colours.put("WHITE", "#FFFFFF");

// Convert a Map into JSON string.

Gson gson = new Gson();

String json = gson.toJson(colours);

System.out.println("json = " + json);

// Convert JSON string back to Map.

Type type = new TypeToken<map<string, string="">>() {}.getType();

Map <string, string=""> map = gson.fromJson(json, type);

for (String key: map.keySet()) {

System.out.println("map.get = " + map.get(key));

}

}</string,></map<string,></string,></string,>

Output:

json = {“WHITE”:”#FFFFFF”,”BLUE”:”#0000FF”,”YELLOW”:”#FFFF00″,”GREEN”:”#008000″,”BLACK”:”#000000″,”RED”:”#FF0000″}
map.get = #FFFFFF
map.get = #0000FF
map.get = #FFFF00
map.get = #008000
map.get = #000000
map.get = #FF0000

Share This Post On:

Related Posts

Iterate Map in Java with Example

Java – Read JSON Data Simple Example

Java – Write JSON Data Simple Example