How to Convert a HashSet to JSON in Java? - Coding

In Java, a HashSet is an implementation of the Set interface that uses a hash table to store elements. It allows fast lookups and does not allow duplicate elements. Elements in a HashSet are unordered and can be of any object type. In this article, we will see how to convert a HashSet to JSON in Java.

Steps to convert a HashSet to JSON in Java

Below are the steps and implementation of converting a HashSet to JSON in Java with Jackson.

Step 1: Create a Maven Project

Open any preferred IDE and Create a new Maven project. Here, we are using IntelliJ IDEA. So, we can do this by selecting File -> New -> Project.. -> Maven and following the wizard.

Project Creation

Project Structure:

Below is the project structure that we have created.

Project Structure

Step 2: Add Jackson Dependency to the pom.xml

Now, we will add Jackson dependency to pom.xml file.

XML

<?xml version="1.0" encoding="UTF-8"?> 
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> 
    <modelVersion>4.0.0</modelVersion> 
  
    <groupId>org.example</groupId> 
    <artifactId>HashSet</artifactId> 
    <version>1.0-SNAPSHOT</version> 
    <dependencies> 
        <dependency> 
            <groupId>com.fasterxml.jackson.core</groupId> 
            <artifactId>jackson-databind</artifactId> 
            <version>2.13.0</version> 
        </dependency> 
    </dependencies> 
    <properties> 
        <maven.compiler.source>21</maven.compiler.source> 
        <maven.compiler.target>21</maven.compiler.target> 
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> 
    </properties> 
  
</project>

Step 3: Add logic of Conversion of a HashSet to JSON String

Below is the implementation to convert a HashSet to JSON with Jackson.

Java

// Java Program for Conversion of a HashSet to JSON String 
package org.example; 
import com.fasterxml.jackson.core.JsonProcessingException; 
import com.fasterxml.jackson.databind.ObjectMapper; 
import com.fasterxml.jackson.databind.ObjectWriter; 
import java.util.HashSet; 
  
// Main Class 
public class Main { 
      // main function 
    public static void main(String[] args) 
    { 
        // Create a HashSet of courses 
        HashSet<String> courses = new HashSet<>(); 
        courses.add("Java"); 
        courses.add("Python"); 
        courses.add("C++"); 
  
        // Create ObjectMapper 
        ObjectMapper mapper = new ObjectMapper(); 
  
        try { 
            // Create ObjectWriter with default pretty printer 
            ObjectWriter writer = mapper.writerWithDefaultPrettyPrinter(); 
              
            // Convert HashSet to JSON 
            String jsonData = writer.writeValueAsString(courses); 
              
            // Print JSON Data 
            System.out.println(jsonData); 
        } 
        catch (JsonProcessingException e) { 
            e.printStackTrace(); 
        } 
    } 
} 

Explanation of the above code:

It creates a HashSet of courses – Java, Python, C++
Jackson ObjectMapper is used to convert Java objects to JSON.
ObjectWriter is used to format the JSON with proper indentation.
HashSet is converted to a JSON string using ObjectWriter.
The JSON string is printed to the output.

Output:

JSON String output

Reffered: https://www.geeksforgeeks.org

Java

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Category:	Coding
Sub Category:	Tutorial
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