Learn in depth the principles and programming techniques of Java multithreading

Comprehensively understand the basic concepts and programming skills of Java multi-threading

In the world of object-oriented programming, the Java language has become a popular language with its stability and cross-platform characteristics. Popular choice. Multi-threaded programming has become one of the important means to improve the performance of Java applications. Understanding the basic concepts and programming skills of Java multithreading will help developers better apply multithreading technology to improve the concurrent performance of applications.

1. The basic concept of multi-threading
   Multi-threading refers to the simultaneous execution of multiple threads in a program. Each thread can perform different tasks, thereby achieving parallel processing. Java uses the Thread class and Runnable interface to implement multi-threading.

The Thread class is a core class in Java that can be inherited to create threads. Subclasses that inherit the Thread class need to override the run method and define the tasks that the thread needs to perform in this method. After creating a thread object, you can start the thread by calling the start method.

The Runnable interface is a functional interface that defines a task that can be executed by a thread. Classes that implement the Runnable interface need to implement the run method and define the tasks that the thread needs to perform in this method. Unlike inheriting the Thread class, implementing the Runnable interface can make the class more flexible because Java does not support multiple inheritance.

2. Multi-threaded programming skills
   2.1 Synchronization and mutual exclusion
   In multi-thread programming, if multiple threads access a shared resource at the same time, data inconsistency or exceptions may occur. To solve this problem, you can use the synchronized keyword to achieve synchronization. The keyword synchronized can modify a method or code block to ensure that only one thread can execute the code modified by synchronized at the same time.

Sample code:

public class Counter {
    private int count;

    public synchronized void increment() {
        count++;
    }
}

2.2 Thread communication
Thread communication allows threads to cooperate with each other and complete tasks together. Java provides three methods: wait, notify, and notifyAll to implement communication between threads. Among them, the wait method puts the thread into a waiting state until it is awakened by other threads calling the notify or notifyAll method; the notify method wakes up the waiting thread; and the notifyAll method wakes up all waiting threads.

Sample code:

public class MessageQueue {
    private String message;
    private boolean hasMessage;

    public synchronized void putMessage(String message) {
        while (hasMessage) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        this.message = message;
        hasMessage = true;
        notifyAll();
    }

    public synchronized String getMessage() {
        while (!hasMessage) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        String msg = message;
        hasMessage = false;
        notifyAll();
        return msg;
    }
}

2.3 Thread pool
Creating threads is expensive, and improper management of the number of threads may cause system resources to be exhausted. Use a thread pool to manage the number of threads, reuse created threads, and control the execution order and priority of threads. Java provides the Executor and ExecutorService interfaces and the ThreadPoolExecutor implementation class to implement thread pools.

Sample code:

public class ThreadPoolExample {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 100; i++) {
            final int taskIndex = i;
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println("执行任务：" + taskIndex);
                }
            });
        }
        executor.shutdown();
    }
}

Through the above introduction, it can be seen that Java multi-thread programming involves synchronization and mutual exclusion, thread communication and thread pool and other technologies. Understanding these basic concepts and programming techniques can help developers better apply multi-threading technology to improve the concurrent performance of Java applications.

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