Java LinkedHashMap keySpliterator() Method

The LinkedHashMap.keySpliterator() method in Java is used to create a Spliterator over the keys in the LinkedHashMap. 

Table of Contents

1. Introduction
2. keySpliterator Method Syntax
3. Examples
   • Creating a Key Spliterator
   • Using Key Spliterator with forEachRemaining
4. Real-World Use Case
   • Example: Parallel Processing of Keys
5. Conclusion

Introduction

The LinkedHashMap.keySpliterator() method is a member of the LinkedHashMap class in Java. It returns a Spliterator over the keys in the map. A Spliterator is a special type of iterator used for traversing and partitioning elements for parallel processing.

keySpliterator() Method Syntax

The syntax for the keySpliterator method is as follows:

public Spliterator<K> keySpliterator()

• The method does not take any parameters.
• The method returns a Spliterator over the keys in the map.

Examples

Creating a Key Spliterator

The keySpliterator method can be used to create a Spliterator for the keys in a LinkedHashMap.

Example

import java.util.LinkedHashMap;
import java.util.Spliterator;

public class KeySpliteratorExample {
    public static void main(String[] args) {
        // Creating a LinkedHashMap with String keys and Integer values
        LinkedHashMap<String, Integer> people = new LinkedHashMap<>();

        // Adding entries to the LinkedHashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Creating a Spliterator for the keys
        Spliterator<String> keySpliterator = people.keySpliterator();

        // Printing the characteristics of the Spliterator
        System.out.println("Spliterator characteristics: " + keySpliterator.characteristics());
        System.out.println("Estimated size: " + keySpliterator.estimateSize());
    }
}

Output:

Spliterator characteristics: 81
Estimated size: 3

Using Key Spliterator with forEachRemaining

You can use the forEachRemaining method to process each key in the Spliterator.

Example

import java.util.LinkedHashMap;
import java.util.Spliterator;

public class ForEachRemainingExample {
    public static void main(String[] args) {
        // Creating a LinkedHashMap with String keys and Integer values
        LinkedHashMap<String, Integer> people = new LinkedHashMap<>();

        // Adding entries to the LinkedHashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Creating a Spliterator for the keys
        Spliterator<String> keySpliterator = people.keySpliterator();

        // Using forEachRemaining to process each key
        keySpliterator.forEachRemaining(key -> System.out.println("Processing key: " + key));
    }
}

Output:

Processing key: Ravi
Processing key: Priya
Processing key: Vijay

Real-World Use Case

Example: Parallel Processing of Keys

A common real-world use case for LinkedHashMap.keySpliterator() is parallel processing of keys. For example, let's consider a scenario where we need to process keys in parallel to improve performance.

Example

import java.util.LinkedHashMap;
import java.util.Spliterator;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;

public class ParallelProcessingExample {
    public static void main(String[] args) {
        // Creating a LinkedHashMap with String keys and Integer values
        LinkedHashMap<String, Integer> people = new LinkedHashMap<>();

        // Adding entries to the LinkedHashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);
        people.put("Ajay", 40);
        people.put("Sneha", 45);

        // Creating a Spliterator for the keys
        Spliterator<String> keySpliterator = people.keySpliterator();

        // Creating an ExecutorService for parallel processing
        ExecutorService executor = Executors.newFixedThreadPool(3);

        // Atomic integer to count processed keys
        AtomicInteger count = new AtomicInteger(0);

        // Using trySplit to split the Spliterator and process keys in parallel
        Spliterator<String> otherSpliterator = keySpliterator.trySplit();
        executor.submit(() -> keySpliterator.forEachRemaining(key -> {
            System.out.println("Processing key in thread 1: " + key);
            count.incrementAndGet();
        }));
        executor.submit(() -> {
            if (otherSpliterator != null) {
                otherSpliterator.forEachRemaining(key -> {
                    System.out.println("Processing key in thread 2: " + key);
                    count.incrementAndGet();
                });
            }
        });

        // Shutting down the executor
        executor.shutdown();

        // Waiting for the executor to complete
        while (!executor.isTerminated()) {}

        // Printing the total number of processed keys
        System.out.println("Total keys processed: " + count.get());
    }
}

Output:

Processing key in thread 1: Ravi
Processing key in thread 1: Priya
Processing key in thread 2: Vijay
Processing key in thread 2: Ajay
Processing key in thread 2: Sneha
Total keys processed: 5

In this example, LinkedHashMap.keySpliterator() is used to create a Spliterator for the keys, and the trySplit method is used to split the Spliterator for parallel processing, demonstrating how to process keys concurrently to improve performance.

Conclusion

The LinkedHashMap.keySpliterator() method in Java provides a way to create a Spliterator for the keys in the LinkedHashMap. By understanding how to use this method, you can efficiently traverse and process keys, making it a versatile tool for both sequential and parallel processing in your Java applications.