introduction
Multithreaded programming has become a must-have skill in today's software development world. With the development of computer hardware, the use of parallel computing capabilities of multi-core processors has become the key to improving program performance and response time. In Java, we can use multithreading to realize concurrent programming and give full play to the potential of the computer. This article will delve into the principles, techniques, and best practices of Java multithreaded programming to help you better understand the world of concurrent programming.
What is multithreaded programming?
In traditional single-threaded programming, programs are executed sequentially. However, in multithreaded programming, a program can execute multiple threads simultaneously, and each thread can independently perform different tasks. This allows us to execute multiple tasks in parallel, improving program performance and response time.
Multithreading in Java
Java provides a rich set of APIs and tools for multithreaded programming. We can use java.lang.Threadclasses to create and manage threads, and we can also use java.util.concurrenttool classes in the package to implement more advanced concurrent operations. Let's dive into the various aspects of multithreading in Java.
create thread
In Java, we can create threads by inheriting Threadclasses or implementing interfaces. RunnableHere is Threadsample code using inherited classes:
public class MyThread extends Thread {
public void run() {
// 线程执行的代码
}
}
// 创建并启动线程
MyThread thread = new MyThread();
thread.start();
Another common way to create threads is to implement Runnablean interface. The following is sample code using the implement Runnableinterface:
public class MyRunnable implements Runnable {
public void run() {
// 线程执行的代码
}
}
// 创建并启动线程
Thread thread = new Thread(new MyRunnable());
thread.start();
When using multithreading, we should follow the recommendations in Alibaba's Java Development Manual. It clearly states that interfaces should be preferred Runnableover inherited Threadclasses to create threads. This is because inheriting Threadclasses breaks the single responsibility principle of classes, while implementing Runnableinterfaces can better follow the principles of object-oriented design. Additionally, using a thread pool provides better management and control over thread creation and resource consumption.
thread synchronization
In multithreaded programming, we need to pay attention to the safety and synchronization between threads. Java provides various mechanisms to achieve thread synchronization such as synchronizedkeywords and Lockinterfaces. synchronizedThe following is a sample code for thread synchronization using keywords:
public class Counter {
private int count;
public synchronized void increment() {
count++;
}
}
When using synchronizedkeywords, we should follow the specifications in Alibaba's Java Development Manual. It states that the scope of code blocks should be minimized and keywords synchronizedshould be avoided in methods . synchronizedAlso, interfaces should be used Lockinstead of synchronizedkeywords, because Lockinterfaces provide more flexible and fine-grained locking control.
inter-thread communication
In multithreaded programming, threads need to communicate and coordinate. Java provides methods such wait()as , notify()and and notifyAll()so on to realize the communication between threads. The following is sample code for inter-thread communication using wait()and methods:notify()
public class Message {
private String content;
private boolean isAvailable = false;
public synchronized String receive() throws InterruptedException {
while (!isAvailable) {
wait();
}
isAvailable = false;
notifyAll();
return content;
}
public synchronized void send(String message) throws InterruptedException {
while (isAvailable) {
wait();
}
content = message;
isAvailable = true;
notifyAll();
}
}
When communicating between threads, we should follow the specifications in Alibaba's Java Development Manual. It states that whileloops should be used instead of ifstatements to check conditions to prevent spurious wakeups. notifyAll()Also, instead of , should be used notify()to wake up waiting threads to avoid thread starvation problems.
Thread Pool
In order to improve the efficiency and resource utilization of multithreading, Java provides a thread pool. Through the thread pool, we can reuse threads to avoid frequent creation and destruction of threads. The following is a sample code using ExecutorServicecreate thread pool:
ExecutorService executor = Executors.newFixedThreadPool(5);
for (int i = 0; i < 10; i++) {
executor.submit(new MyRunnable());
}
executor.shutdown();
When using the thread pool, we should follow the specifications in Alibaba's Java Development Manual. It states that the method should be called explicitly shutdown()to shut down the thread pool in order to release resources. Also, submitting a large number of tasks in a loop should be avoided to prevent the thread pool from being exhausted.
Best Practices and Considerations
When doing multi-threaded programming, there are some best practices and considerations that we need to pay attention to:
- Avoid race conditions and deadlocks, and use appropriate synchronization mechanisms to ensure thread safety.
- Try to avoid using shared data to reduce competition and synchronization overhead between threads.
- Use thread pool to manage and reuse threads, avoid frequent creation and destruction of threads.
- Pay attention to the priority and scheduling of threads, and arrange the execution order and time slice allocation of tasks reasonably.
- Use appropriate tools and techniques to debug and analyze multithreaded programs, such as thread dumps and performance analysis tools.
in conclusion
Java multi-thread programming is a powerful technology that can make full use of the computer's parallel computing capabilities to improve program performance and response time. By understanding and mastering the principles, techniques and best practices of Java multithreading, we can write efficient and reliable concurrent programs. However, multi-threaded programming also brings some challenges and risks. We need to use it carefully and pay attention to thread safety and synchronization issues.
I hope this article helps you understand and apply Java multi-threaded programming. By mastering the fundamentals and techniques of multithreaded programming, you can develop greater creativity and flexibility in software development. Let's explore the wonderful world of concurrent programming together!
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