GSON - Array and Multi Dimensional Array Example

In this quick article, we show you how to serialize and deserialize an array or a multidimensional array to and from its JSON representation.

GSON Maven Dependency

To use Gson with Maven2/3, you can use the Gson version available in Maven Central by adding the following dependency:
<dependencies>
    <dependency>
      <groupId>com.google.code.gson</groupId>
      <artifactId>gson</artifactId>
      <version>2.8.5</version>
      <scope>compile</scope>
    </dependency>
</dependencies>

Serializing and Deserializing Integer Array

This example serializes and deserializes an Integer Array to and from JSON representation.
Gson gson = new Gson();
int[] marks = { 100, 90, 85 };
System.out.print("marks:" + gson.toJson(marks) + ",");

// De-serialization
marks = gson.fromJson("[100,90,85]", int[].class);
System.out.println("marks:" + Arrays.toString(marks));
Output:
marks:[100,90,85],marks:[100, 90, 85]

Serializing and Deserializing String Array

This example serializes and deserializes a String Array to and from JSON representation.
Gson gson = new Gson();
String[] names = { "Ram", "Shyam", "Mohan" };

// serialization
System.out.print("names:" + gson.toJson(names));
System.out.println("}");

// De-serialization
names = gson.fromJson("[\"Ram\",\"Shyam\",\"Mohan\"]", String[].class);
System.out.println("names:" + Arrays.toString(names));
Output:
names:["Ram","Shyam","Mohan"]}
names:[Ram, Shyam, Mohan]

Serializing and Deserializing Custom Array of user objects

This example serializes and deserializes a User Array to and from JSON representation. Let's first create User POJO class:
package net.javaguides.gson;

public class User {

    private transient int id;
    private String firstName;
    private String lastName;
    private int age;
    private String gender;
    private String password;

    public int getId() {
        return id;
    }

    public void setId(int i) {
        this.id = i;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", age=" + age + ", gender=" +
            gender + "]";
    }
}
package net.javaguides.gson;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class GSONArrayExamples {
    public static void main(String[] args) {
        Gson gson = new GsonBuilder().setPrettyPrinting().create();

        User[] users = new User[2];
        User user = new User();
        user.setFirstName("Ramesh");
        user.setLastName("Fadatare");
        user.setGender("Male");
        user.setAge(28);
        user.setId(100);

        User user1 = new User();
        user1.setFirstName("John");
        user1.setLastName("Cena");
        user1.setGender("Male");
        user1.setAge(50);
        user1.setId(101);

        users[0] = user;
        users[1] = user1;

        // Serialization users
        System.out.println(gson.toJson(users));


        String usersJsonArray = "[\r\n" +
            "  {\r\n" +
            "    \"firstName\": \"Ramesh\",\r\n" +
            "    \"lastName\": \"Fadatare\",\r\n" +
            "    \"age\": 28,\r\n" +
            "    \"gender\": \"Male\"\r\n" +
            "  },\r\n" +
            "  {\r\n" +
            "    \"firstName\": \"John\",\r\n" +
            "    \"lastName\": \"Cena\",\r\n" +
            "    \"age\": 50,\r\n" +
            "    \"gender\": \"Male\"\r\n" +
            "  }\r\n" +
            "]";
        // De-Serialization users
        System.out.println(gson.fromJson(usersJsonArray, User[].class));
    }
}
Output:
[
  {
    "firstName": "Ramesh",
    "lastName": "Fadatare",
    "age": 28,
    "gender": "Male"
  },
  {
    "firstName": "John",
    "lastName": "Cena",
    "age": 50,
    "gender": "Male"
  }
]
[Lnet.javaguides.gson.User;@7aec35a

Serializing and Deserializing Multi-Dimensional Array

This example demonstrates how to serialize and deserialize a multi-dimensional array to and from JSON representation.
package net.javaguides.gson;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class GSONArrayExamples {
    public static void main(String[] args) {
        multiDimensionalArray();
    }

    private static void multiDimensionalArray() {
        Gson gson = new GsonBuilder().create();
        int[][] multiIntArray = new int[][] {
            {
                1,
                2,
                3
            }, {
                4,
                5,
                6
            }
        };

        // serialization
        gson.toJson(multiIntArray); // => [[1,2,3],[4,5,6]]

        // deserialization
        int[][] intArray2 = gson.fromJson("[[1,2,3],[4,5,6]]", int[][].class);
    }
}

Reference

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