ArrayList spliterator() method in Java

The spliterator() method of ArrayList returns a Spliterator of the same elements as ArrayList but created Spliterator is late-binding and fail-fast. A late-binding Spliterator binds to the source of elements. It means that Arraylist at the point of the first traversal, first split, or the first query for estimated size, rather than at the time the Spliterator is created. It can be used with Streams in Java 8. Also, it can traverse elements individually and in bulk too. Spliterator is a better way to traverse over element because it provides more control over elements.

Spliterator = Splitting + Iterator

• It uses tryAdvance() method to iterate elements individually in multiple Threads to support Parallel Processing,
• forEachRemaining() method to iterate elements sequentially in a single Thread,
• trySplit() method to divide itself into Sub-Spliterators to support Parallel Processing.

Spliterator supports both Sequential and Parallel processing of data. If you observe the output of below program’s output, you will find Spliterator.forEachRemaining() method works in the same way as ArrayList.foreach() but it provides better performance. Syntax:

public Spliterator<E> spliterator()

Returns: This method returns a Spliterator over the elements in ArrayList. Below programs illustrate spliterator() method of ArrayList: 

Example 1: To demonstrate spliterator() method on ArrayList which contains a list of emails. 

Java

// Java Program Demonstrate spliterator()
// method of ArrayList

import java.util.*;

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

        // create an ArrayList which contains
        // emails for a group of people
        ArrayList<String> list = new ArrayList<String>();

        // Add emails to list
        list.add("abc@geeksforgeeks.org");
        list.add("user@geeksforgeeks.org");
        list.add("pqr@geeksforgeeks.org");
        list.add("random@geeksforgeeks.org");
        list.add("randomuser@geeksforgeeks.org");

        // create Spliterator of ArrayList
        // using spliterator() method
        Spliterator<String> emails = list.spliterator();

        // print result from Spliterator
        System.out.println("list of Emails:");

        // forEachRemaining method of Spliterator
        emails.forEachRemaining(
            (n) -> System.out.println(n));
    }
}

Output:

list of Emails:
abc@geeksforgeeks.org
user@geeksforgeeks.org
pqr@geeksforgeeks.org
random@geeksforgeeks.org
randomuser@geeksforgeeks.org

Example 2: To demonstrate spliterator() method on ArrayList which contains list of Users. 

Java

// Java Program Demonstrate spliterator()
// method of ArrayList

import java.util.*;

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

        // create an ArrayList which contains
        // user details from user class
        ArrayList<user> list = new ArrayList<user>();

        // Add emails to list
        list.add(new user("Aman", 24));
        list.add(new user("Suraj", 23));
        list.add(new user("Amar", 24));
        list.add(new user("Kajal", 22));

        // create Spliterator of ArrayList
        // using spliterator() method
        Spliterator<user> users = list.spliterator();

        // print result from Spliterator
        System.out.println("list of Emails:");

        // forEachRemaining method of Spliterator
        users.forEachRemaining((n) -> print(n));
    }

    public static void print(user u)
    {
        System.out.println("User name : " + u.name
                           + " and user age: " + u.age);
    }
}

// create a user class
class user {

    String name;
    int age;

    user(String name, int age)
    {
        this.name = name;
        this.age = age;
    }
}

Output:

list of Emails:
User name : Aman and user age: 24
User name : Suraj and user age: 23
User name : Amar and user age: 24
User name : Kajal and user age: 22

Example 3:

Java

import java.io.*;
import java.util.ArrayList;
import java.util.Spliterator;

public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        ArrayList<String> names = new ArrayList<>();

        // Adding elements to List
        names.add("Kumar");
        names.add("Bob");
        names.add("Raj");
        names.add("David");
        names.add("Eve");

        Spliterator<String> spliterator
            = names.spliterator();

        spliterator.forEachRemaining(System.out::println);
    }
}

Output

Kumar
Bob
Raj
David
Eve