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How to convert array into JSON?

In the example below you can see how to convert an array into JSON string. We serialize the array to JSON using the Gson.toJson() method. To deserialize a string of JSON into array we use the Gson.fromJson() method.

package com.javacoderanch.example.google.gson;

import com.google.gson.Gson;

public class ArrayToJson {
    public static void main(String[] args) {
        int[] numbers = {1, 1, 2, 3, 5, 8, 13};
        String[] days = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};

        //
        // Create a new instance of Gson
        //
        Gson gson = new Gson();

        //
        // Convert numbers array into JSON string.
        //
        String numbersJson = gson.toJson(numbers);

        //
        // Convert strings array into JSON string
        //
        String daysJson = gson.toJson(days);
        System.out.println("numbersJson = " + numbersJson);
        System.out.println("daysJson = " + daysJson);

        //
        // Convert from JSON string to a primitive array of int.
        //
        int[] fibonacci = gson.fromJson(numbersJson, int[].class);
        for (int i = 0; i < fibonacci.length; i++) {
            System.out.print(fibonacci[i] + " ");
        }
        System.out.println("");

        //
        // Convert from JSON string to a string array.
        //
        String[] weekDays = gson.fromJson(daysJson, String[].class);
        for (int i = 0; i < weekDays.length; i++) {
            System.out.print(weekDays[i] + " ");
        }
        System.out.println("");

        //
        // Converting multidimensional array into JSON
        //
        int[][] data = {{1, 2, 3}, {3, 4, 5}, {4, 5, 6}};
        String json = gson.toJson(data);
        System.out.println("Data = " + json);

        //
        // Convert JSON string into multidimensional array of int.
        //
        int[][] dataMap = gson.fromJson(json, int[][].class);
        for (int i = 0; i < data.length; i++) {
            for (int j = 0; j < data[i].length; j++) {
                System.out.print(data[i][j] + " ");
            }
            System.out.println("");
        }
    }
}

Here is our code result:

numbersJson = [1,1,2,3,5,8,13]
daysJson = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]
1 1 2 3 5 8 13 
Sun Mon Tue Wed Thu Fri Sat 
Data = [[1,2,3],[3,4,5],[4,5,6]]
1 2 3 
3 4 5 
4 5 6