How to Convert Comma Separated String to HashSet in Java?

Given a Set of String, the task is to convert the Set to a comma-separated String in Java.

Examples:

Input: Set<String> = ["Geeks", "ForGeeks", "GeeksForGeeks"]
Output: "Geeks, For, Geeks"

Input: Set<String> = ["G", "e", "e", "k", "s"]
Output: "G, e, e, k, s" 

There are two ways in which we can convert comma separated string to Java HashSet :

Method 1: Using the String split method and Arrays class

• First, we will split the string by comma and that will return us an array. 
• Once we get an array, we will convert it to the List using the asList() method of the Arrays class. 
• The List object then can be converted to the HashSet using the HashSet constructor.

Java

// Java program to convert comma
// separated string to HashSet

import java.util.Arrays;
import java.util.HashSet;
import java.util.List;

public class StringToHashSetExample {

    public static void main(String[] args) {

        String str = "1,2,3,4,2,5";

        // split the string by comma
        String[] strParts = str.split(",");

        // convert array to the List using asList method
        List<String> listParts = Arrays.asList(strParts);

        // create HashSet from the List using constructor
        HashSet<String> hsetFromString = new HashSet<String>( listParts );

        System.out.println("HashSet contains: " + hsetFromString);
    }
}

Output

HashSet contains: [1, 2, 3, 4, 5]

Method 2: Using Java 8 stream

• If you are using Java version 8 or later, you can also use the stream to convert comma separated string to Set<String> object as given below.

Java

// Java program to convert comma
// separated string to HashSet

import java.util.*;
import java.io.*;
import java.util.stream.*;

public class StringToHashSetExample {

    public static void main(String[] args)
    {

        String str = "1,2,3,4,2,5";

        Set<String> set
            = Stream.of(str.trim().split("\\s*,\\s*"))
                  .collect(Collectors.toSet());

        System.out.println("HashSet contains: " + set);
    }
}

Output

HashSet contains: [1, 2, 3, 4, 5]