Synchronization Blocks in Java
Table of Contents
- Introduction
- Understanding Synchronization Blocks in Java
- What is Synchronization?
- Why Use Synchronization Blocks?
- Implementing Synchronization Blocks
- Code Walkthrough
- Detailed Explanation of the Code
- Performance Comparison
- Conclusion
1. Introduction
In Java, multithreading allows multiple threads to run concurrently, but it also presents challenges such as thread interference and memory consistency errors. One of the key mechanisms to handle these issues is synchronization, which ensures that shared resources are accessed by only one thread at a time.
This article focuses on synchronization blocks in Java, explaining their use, advantages, and a real-world code example. By the end, you’ll understand how to implement synchronization blocks and when to use them over synchronization methods.
2. Understanding Synchronization Blocks in Java
2.1 What is Synchronization?
In multithreaded programming, synchronization is a technique that controls the access of multiple threads to shared resources. Without synchronization, it’s possible for one thread to modify a shared object while another is still using it, leading to unpredictable results.
2.2 Why Use Synchronization Blocks?
Synchronization methods are the simplest way to synchronize threads, but they can be inefficient because the entire method is locked. A synchronization block allows you to limit the scope of synchronization to a particular section of code, improving performance by reducing the amount of locked code.
| Feature | Synchronized Method | Synchronized Block |
|---|---|---|
| Scope of Locking | Entire method | Specific block |
| Performance Impact | Higher | Lower |
| Use Case | Simpler scenarios | Performance-sensitive sections |
3. Implementing Synchronization Blocks
3.1 Code Walkthrough
Here’s a simple example of using a synchronization block to manage multithreading:
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class Brackets { public void generate() throws InterruptedException { synchronized(this) { for (int i = 1; i <= 20; i++) { Thread.sleep(5); if (i <= 10) { System.out.print('['); } else { System.out.print(']'); } } System.out.println(); } for (int i = 0; i < 10; i++) { Thread.sleep(10); } } } public class Main { public static void main(String[] args) { Brackets brackets = new Brackets(); new Thread(new Runnable() { @Override public void run() { long startTime = System.currentTimeMillis(); for (int i = 0; i < 5; i++) { try { brackets.generate(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println("Time: " + (System.currentTimeMillis() - startTime)); } }).start(); } } |
3.2 Detailed Explanation of the Code
Class Brackets: The generate() method in this class contains a synchronized block that ensures only one thread can execute the code inside the block at a time.
Synchronization Block: The synchronized(this) block ensures that the thread holds the lock for the instance of the Brackets object.
Thread Execution: The Main class creates a new thread that repeatedly calls the generate() method. The synchronization block allows the method to be executed by one thread at a time, preventing interference.
4. Performance Comparison
As mentioned in the code comments, using synchronization methods vs. synchronization blocks can have different performance impacts:
- Synchronization Method: Takes approximately 4100 milliseconds.
- Synchronization Block: Takes approximately 3000 milliseconds.
This performance difference occurs because synchronization blocks restrict the locked section to critical code, allowing other threads to execute non-critical sections without delay.
5. Conclusion
Synchronization blocks offer a fine-grained approach to multithreaded synchronization in Java. By locking only the necessary portion of the code, they improve performance compared to synchronized methods. Developers should choose synchronization blocks when working on performance-critical multithreaded applications.