An introductory tutorial on concurrent programming using Java

Java is one of the most popular programming languages ​​today, and Java's concurrent programming is one of its most powerful features. Java's concurrent programming allows us to use multi-threads to process tasks concurrently and improve the running efficiency of the program. This article will introduce the basic knowledge and practical operations of Java's concurrent programming in detail, and help readers understand the basic concepts and coding methods of Java's concurrent programming.

1. The concept of concurrent programming

Concurrent programming refers to the ability of multiple threads to execute a piece of code at the same time. The number of threads in the program determines how many concurrencies the program has, so concurrent programming is multi-threaded programming. For Java, threads can be created and managed through Java Thread.

Thread is the smallest execution unit in Java. Each Java program has a main thread, and the thread is used to control the execution of the program. When you need to start other threads, you can call the Java Thread class to construct a new thread. In Java, the number of threads running simultaneously is limited. Multi-threaded programming can be used to maximize the use of modern computer hardware resources and improve the running efficiency of the program.

2. Methods to implement concurrent programming in Java

1. Use the Thread class to create and start threads

The Thread class in Java is the key class for creating and managing threads , threads are created in the program by inheriting the Thread class or implementing the Runnable interface. Example of using the Thread class to create and start a thread:

class MyClass extends Thread { 
    public void run() { 
        // 线程执行的代码
    }
}

public class Main { 
    public static void main(String[] args) { 
        MyClass thread = new MyClass(); 
        thread.start(); // 开始执行线程
    }
}

2. Implementing the Runnable interface

class MyClass implements Runnable { 
    public void run() { 
        // 线程执行的代码
    }
}

public class Main { 
    public static void main(String[] args) { 
        Thread thread = new Thread(new MyClass()); 
        thread.start(); // 开始执行线程
    }
}

3. Thread synchronization method

Thread synchronization refers to shared access by multiple threads Resource technology is a technology that ensures that they reasonably calculate and obtain shared resources in a certain order. Thread synchronization in Java can be ensured through the Synchronized keyword, which can modify methods and code blocks to ensure that only subsequent threads can access critical resources.

class MyClass { 
    private int count; 
    public synchronized void increase() { 
        count++; 
    }
} 

4. Thread waiting method

In Java, we can also use the wait() method to wait for the end of thread execution, and use the notify() and notifyAll() methods to notify the concurrent execution of the next Round tasks.

5. Thread interruption method

In Java, thread interruption can be achieved by calling the interrupt() method, and using the isInterrupted() method to determine whether it has been interrupted.

class MyClass extends Thread { 
    private volatile boolean flag = true; 

    public void run() { 
        while (flag) { 
            // 线程执行的代码
        } 
    }

    public void stopThread() { 
        flag = false; 
        interrupt(); // 中断线程
    }
}

3. Precautions for concurrent programming in Java

1. Thread performance issues

When creating multiple threads, you should pay attention to the number of threads. Too many threads may cause The CPU is overloaded, affecting system performance.

2. Deadlock problem

When multiple threads occupy some key resources at the same time, a deadlock problem may occur, causing the program to be unable to continue execution. Therefore, developers need to properly plan and manage resource sharing between threads.

3. Race condition problem

A race condition refers to a situation where an error occurs in the program state due to concurrent execution. When multiple threads access shared resources at the same time, their execution order may be interleaved, resulting in program execution errors. At this point, synchronization is required to avoid race condition issues.

4. Conclusion

This article introduces the basic concepts and operation methods of concurrent programming in Java, including thread creation, startup, synchronization, waiting and interruption, etc. When writing multi-threaded code, you need to pay attention to thread performance issues, deadlock issues, and race conditions. Through studying this article, I believe that readers can master the basic knowledge of concurrent programming and provide a solid foundation for the concurrency mechanism of Java programming.

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