Java StreamSupport

Introduction

StreamSupport is a utility class in Java’s java.util.stream package that provides methods for creating streams from spliterators. It allows for more customized stream creation, especially useful when working with custom data structures.

Table of Contents

1. What is StreamSupport?
2. Creating a Stream with StreamSupport
3. Common Methods
4. Examples of StreamSupport
5. Real-World Use Case
6. Conclusion

1. What is StreamSupport?

StreamSupport is a utility class that provides static methods for creating sequential or parallel streams from spliterators, offering flexibility in stream generation.

2. Creating a Stream with StreamSupport

You can create streams using StreamSupport with the following methods:

• StreamSupport.stream(Spliterator<T> spliterator, boolean parallel): Creates a stream from a spliterator.
• StreamSupport.intStream(Spliterator.OfInt spliterator, boolean parallel): Creates an IntStream from an int spliterator.
• StreamSupport.longStream(Spliterator.OfLong spliterator, boolean parallel): Creates a LongStream from a long spliterator.
• StreamSupport.doubleStream(Spliterator.OfDouble spliterator, boolean parallel): Creates a DoubleStream from a double spliterator.

3. Common Methods

• stream: Creates a regular stream from a spliterator.
• intStream: Creates an IntStream from an int spliterator.
• longStream: Creates a LongStream from a long spliterator.
• doubleStream: Creates a DoubleStream from a double spliterator.

4. Examples of StreamSupport

Example 1: Creating a Stream from a Custom Spliterator

This example demonstrates how to create a stream from a custom spliterator using StreamSupport.

import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.StreamSupport;

public class CustomSpliteratorExample {
    public static void main(String[] args) {
        Spliterator<String> spliterator = Spliterators.spliterator(new String[]{"Arjun", "Bhavna", "Chirag"}, 0);

        StreamSupport.stream(spliterator, false)
                     .forEach(System.out::println);
    }
}

Output:

Arjun
Bhavna
Chirag

Example 2: Creating an IntStream from a Spliterator

This example shows how to create an IntStream from an int array using StreamSupport.

import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.StreamSupport;

public class IntStreamExample {
    public static void main(String[] args) {
        Spliterator.OfInt spliterator = Spliterators.spliterator(new int[]{1, 2, 3, 4, 5}, 0);

        StreamSupport.intStream(spliterator, false)
                     .forEach(System.out::println);
    }
}

Output:

1
2
3
4
5

5. Real-World Use Case: Creating a Stream from a Custom Data Structure

This example illustrates how to create a stream from a custom data structure using a custom spliterator.

import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.stream.StreamSupport;

class Node {
    String name;
    Node next;

    Node(String name, Node next) {
        this.name = name;
        this.next = next;
    }
}

class NodeSpliterator implements Spliterator<String> {
    private Node current;

    NodeSpliterator(Node start) {
        this.current = start;
    }

    @Override
    public boolean tryAdvance(Consumer<? super String> action) {
        if (current != null) {
            action.accept(current.name);
            current = current.next;
            return true;
        }
        return false;
    }

    @Override
    public Spliterator<String> trySplit() {
        return null; // No splitting for simplicity
    }

    @Override
    public long estimateSize() {
        return Long.MAX_VALUE; // Unknown size
    }

    @Override
    public int characteristics() {
        return ORDERED | NONNULL;
    }
}

public class CustomDataStructureExample {
    public static void main(String[] args) {
        Node node3 = new Node("Chirag", null);
        Node node2 = new Node("Bhavna", node3);
        Node node1 = new Node("Arjun", node2);

        NodeSpliterator nodeSpliterator = new NodeSpliterator(node1);

        StreamSupport.stream(nodeSpliterator, false)
                     .forEach(System.out::println);
    }
}

Output:

Arjun
Bhavna
Chirag

Conclusion

StreamSupport provides flexibility for creating streams from custom data structures and spliterators. It enhances the power of the Stream API by allowing more control over the stream creation process, especially when working with non-standard data sources. Using StreamSupport can lead to more versatile and efficient stream processing in Java.