In Java, Thread is the smallest unit of execution within the program. It represents an independent path of execution that can run concurrently with other threads. When dealing with multi-threaded applications, where multiple threads are accessing and modifying data concurrently, it’s crucial to ensure that data structures like ArrayList are handled in a way that prevents conflicts and maintains data integrity.

In this article, we will explore the basic process of making an ArrayList thread-safe in a Java program.

Making ArrayList Thread-Safe in Java

To make ArrayList Thread-Safe, we can follow the below approach:

Syntax:

// It is a general syntax
public static <T> List<T> synchronizedList(List<T> list)  

//Use it for that code
// Create a regular ArrayList
List<T> normalList = new ArrayList<>();

// Make it thread-safe using Collections.synchronizedList
List<T> synchronizedList = Collections.synchronizedList(normalList);

The synchronizedList() method of the Java Collections class is used to get a synchronized (thread-safe) version of a specified list. This method wraps up our original list and returns a synchronized view of it.

Program to make ArrayList Thread-Safe in Java

Iterating over the synchronized list:
Element: Element 1
Element: Element 2
After removing 'Element 1'...
Iterating over the synchronized list after removal:
Element: Element 2

Explanation of the Program:

• In the above program, first we have created a regular ArrayList.
• After that we make it thread-safe using Collections.synchronizedList().
• Now synchronizedList can be used safely in a multi-threaded environment.
• And now operations on the list are automatically get synchronized.
• Now we have added elements to the synchronized list.
• Then, iterating over the synchronized list and modified.
• In final, we have done iteration over the synchronized list again.

To know more about the topic refer to this article Synchronization of ArrayList in Java.