Java Concurrency Best Practices

1. Introduction

Concurrency is the ability of a program to do multiple things simultaneously. In Java, this is achieved through threads. This lesson covers best practices to effectively manage concurrency in Java applications.

2. Key Concepts

2.1 Threads

A thread is the smallest unit of processing that can be scheduled by an operating system.

2.2 Synchronization

Synchronization is a mechanism that ensures that only one thread can access a resource at a time.

2.3 Deadlock

A deadlock occurs when two or more threads are blocked forever, waiting for each other.

3. Best Practices

Tip: Always prefer higher-level concurrency constructs provided by Java over low-level thread management.

Use ExecutorService for managing threads.
Use Callable and Future for tasks that return results.
Prefer immutability for shared data.
Use java.util.concurrent package for concurrent collections.
Avoid using synchronized blocks; prefer using ReentrantLock.

4. Common Patterns

4.1 Producer-Consumer Pattern


import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

public class ProducerConsumer {
    private static BlockingQueue queue = new ArrayBlockingQueue<>(10);

    public static void main(String[] args) {
        Thread producer = new Thread(() -> {
            try {
                for (int i = 0; i < 10; i++) {
                    queue.put(i);
                    System.out.println("Produced: " + i);
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        });

        Thread consumer = new Thread(() -> {
            try {
                for (int i = 0; i < 10; i++) {
                    int value = queue.take();
                    System.out.println("Consumed: " + value);
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        });

        producer.start();
        consumer.start();
    }
}

5. FAQ

What is the difference between synchronized and Lock?

synchronized is a keyword that provides a simple way to lock a method or block, while Lock is an interface that provides more flexibility and features.

What is a thread pool?

A thread pool is a collection of worker threads that efficiently execute asynchronous tasks. It helps in reusing threads, reducing overhead.

How can I avoid deadlock?

To avoid deadlock, ensure that all threads acquire locks in a consistent order.