How to Implement a Thread-Safe Resizable Array in Java? - Coding

Multiple threads may securely execute operations like insertion and deletion without risking data corruption when utilizing a thread-safe resizable array. The ArrayList class is a popular Java class, yet it is not thread-safe by default. We may use concurrent collections or synchronization to make it thread-safe.

Thread-Safe Resizable Array in Java

We may use concurrent collections like CopyOnWriteArrayList or Collections.synchronizedList to create a thread-safe resizable array. Data corruption is avoided via synchronization, which guarantees that only one thread may access the array at a time.

Program to Implement Thread Safe Resizable Array in Java

Using Collections.synchronizedList, let’s examine an example:

Java

// Java Program to Implement Thread Safe Resizable Array 
import java.util.ArrayList;   
import java.util.Collections; 
import java.util.List; 
  
// Driver Class 
public class ThreadSafeResizableArray { 
    // Main Function 
    public static void main(String[] args) { 
        // Creating a thread-safe resizable array 
        List<Integer> threadSafeArray = Collections.synchronizedList(new ArrayList<>()); 
  
        // Adding elements in a thread-safe manner 
        threadSafeArray.add(1); 
        threadSafeArray.add(2); 
        threadSafeArray.add(3); 
  
        // Iterating over the array using a synchronized block 
        synchronized (threadSafeArray) { 
            for (Integer element : threadSafeArray) { 
                System.out.println(element); 
            } 
        } 
    } 
} 

Output

1
2
3

Explaination of the above Program:

In this example, we use Collections.synchronizedList to generate a thread-safe resizable array. An existing list is wrapped by the synchronizedList method, which then produces a synchronized (thread-safe) list.

As an alternative, CopyOnWriteArrayList may be utilized:

Java

// Java Program to Implement Thread Safe Resizable Array 
import java.util.List; 
import java.util.concurrent.CopyOnWriteArrayList; 
  
public class ThreadSafeResizableArray { 
  
    public static void main(String[] args) { 
        // Creating a thread-safe resizable array 
        List<Integer> threadSafeArray = new CopyOnWriteArrayList<>(); 
  
        // Adding elements 
        threadSafeArray.add(1); 
        threadSafeArray.add(2); 
        threadSafeArray.add(3); 
  
        // Iterating over the array 
        for (Integer element : threadSafeArray) { 
            System.out.println(element); 
        } 
    } 
} 

Output

1
2
3

Explaination of the above Program:

Concurrent collections like CopyOnWriteArrayList provide thread safety without requiring explicit synchronization. To ensure safe iteration, it makes a fresh duplicate of the underlying array each time an element is added or changed.

Reffered: https://www.geeksforgeeks.org

Java

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Category:	Coding
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