How to Convert a Comma-Separated String into an ArrayList in Java?

In Java, to convert a comma-separated string into ArrayList, we can use the split() method to break the string into an array based on the comma delimiter. Another method we can also use Java Streams for a functional approach to achieve the same result.

Example:

Input: "Hello,from,geeks,for,geeks"
Output: [Hello, from, geeks, for, geeks]

1. Using split() Method

• The code initializes a string s.
• Then the code uses split() method on the string s and passes `,` separator in the method argument.
• The split() returns an array.
• Arrays.asList() is used to create a List from the array.
• new ArrayList<>() constructs a new ArrayList with the elements from the list.
• In the end, the code prints the ArrayList.

Illustration:

// Java program to Convert a Comma-Separated
// String into an ArrayList using split()
import java.util.*;

class GFG {
    public static void main(String[] args)
    {
        String s = "Hello,from,geeks,for,geeks";
        
        // split the string by comma
        String[] arr = s.split(",");
        
        // Convert the array into arraylist
        ArrayList<String> l = new ArrayList<>(Arrays.asList(arr));

        System.out.println("The ArrayList is: " + l);
    }
}

The ArrayList is: [Hello, from, geeks, for, geeks]

2. Using Java Streams

• The code initializes a string s.
• The code split() the input string into an array of strings using the comma`,` as a delimiter. The split() returns an array of substring.
• Arrays.stream() converts the array of substrings into a stream of strings.
• .collect(Collectors.toCollection(ArrayList :: new)) - This will collect the stream of strings into a new ArrayList through the collector. All the collected elements should be stored in an ArrayList.

Illustration:

// Java Program to Convert a Comma-Separated 
// String into an ArrayList Using Stream
import java.util.*;
import java.util.stream.Collectors;

class GFG {
    public static void main(String[] args) {

        String s = "Hello,from,geeks,for,geeks";
        
        // Split the string by comma and collect into ArrayList
        ArrayList<String> l = Arrays.stream(s.split(",")).collect(Collectors.toCollection(ArrayList::new));

        System.out.println("The ArrayList is: " + l);
    }
}

The ArrayList is: [Hello, from, geeks, for, geeks]