How to Handle Concurrent Access and Modification of a TreeMap Using Concurrent Collections in Java?

To solve data corruption in a multithreaded context, and thread safety, Java offers concurrent collections in the java.util.concurrent package.

In this article, we will learn the use of concurrent collections to manage simultaneous access and change of a TreeMap.

• Concurrent Collections: Java concurrent collections provide thread-safe alternatives for non-concurrent collections.
• ConcurrentNavigableMap Interface: ConcurrentSkipListMap implements the ConcurrentNavigableMap interface, which offers a concurrently navigable version of a map. It allows for simultaneous access and editing while preserving the elements in order.

Program to Manage Concurrent Access and Modification of a TreeMap in Java

Let’s use ConcurrentSkipListMap to see how to manage concurrent access and modification of a TreeMap.

Java

// Java Program to Handle Concurrent Access
// And Modification of a TreeMap using Concurrent Collections
import java.util.concurrent.ConcurrentNavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;

// Driver Class
public class ConcurrentTreeMapExample
{
      // Main Function
    public static void main(String[] args)
    {
        // Creating a concurrent TreeMap
        ConcurrentNavigableMap<Integer, String> concurrentTreeMap = new ConcurrentSkipListMap<>();

        // Creating threads to perform concurrent operations
        Thread writerThread = new Thread(() ->
           {
            for (int i = 0; i < 1000; i++)
            {
                concurrentTreeMap.put(i, "" + i);
            }
        });

        Thread readerThread = new Thread(() ->
           {
            for (int i = 0; i < 1000; i++) {
                System.out.println("Key: " + i + ", Value: " + concurrentTreeMap.get(i));
            }
        });

        // Start threads
        writerThread.start();
        readerThread.start();

        // Wait for threads to finish
        try
        {
            writerThread.join();
            readerThread.join();
        }
        catch (InterruptedException e)
        {
            e.printStackTrace();
        }
    }
}

Output

Key: 0, Value: null
Key: 1, Value: 1
Key: 2, Value: 2
Key: 3, Value: 3
Key: 4, Value: 4
Key: 5, Value: 5
Key: 6, Value: 6
Key: 7, Value: 7
Key: 8, Value: 8
Key: 9, Value: 9
Key: 10, Value: 10
Key: 11,...

Explanation of the above Program:

• We have created a ConcurrentNavigableMap instance named concurrentTreeMap using ConcurrentSkipListMap, which is a concurrent implementation of NavigableMap.
• We have created two threads i.e. writerThread and readerThread.
• The writerThread inserts key-value pairs into the concurrent TreeMap from 0 to 999.
• The readerThread retrieves and prints key-value pairs from the concurrent TreeMap for keys ranging from 0 to 999.
• We have started both the threads using the start() method.
• We use the join() method to wait for both threads to finish their execution before the program exits.