Concurrent programming skills and application practice of Java thread pool

Concurrent programming skills and application practices of Java thread pool

With the popularity of the Internet and mobile Internet, the number of concurrent visits has become larger and larger, and traditional single-thread programming methods can no longer meet the needs of large-scale concurrency. . The Java thread pool makes full use of CPU resources to achieve efficient concurrent programming and is an indispensable part of object-oriented programming.

This article starts from the basic principles of Java thread pool and introduces the core parameter configuration and usage of thread pool, application scenarios of thread pool and its optimization strategy.

1. Basic principles of Java thread pool

Java thread pool is a thread scheduling framework for concurrent programming. It can use idle threads to process new tasks, thereby reducing the cost of thread creation and destruction. , improve the efficiency of the system.

Java thread pool contains three basic components: task queue, worker thread and thread pool manager.

In the Java thread pool, worker threads are the key to performing specific tasks. The thread pool manager is responsible for maintaining the thread pool and allocating tasks, and starting or shutting down the thread pool and worker threads when needed. The task queue is a container that stores tasks. The thread pool manager will take tasks from the queue and dispatch the tasks to idle worker threads for execution.

2. Java thread pool core parameter configuration

The core parameters of Java thread pool include thread pool size, work queue size, maximum thread pool size, thread survival time and rejection policy.

1. Thread pool size:

The thread pool size refers to the maximum number of active threads allowed in the thread pool. For different types of applications, the thread pool size needs to be adjusted appropriately.

2. Work queue size:

The work queue size is the queue size for storing tasks in the thread pool. When the number of working threads reaches the maximum size of the thread pool, new tasks will enter the queue and wait. Processed until the queue is full by the specified reject policy.

3. Maximum size of the thread pool:

The maximum size of the thread pool is the maximum number of worker threads allowed in the thread pool. The maximum size of the thread pool needs to be adjusted appropriately according to system resources, otherwise it may Leading to resource contention and performance degradation.

4. Thread survival time:

Thread survival time refers to the time that a working thread remains alive in an idle state. When the idle thread reaches the specified time, the thread will be recycled until the number of threads is reached. The core size of the thread pool.

5. Rejection policy:

The rejection policy refers to the thread pool's policy of rejecting new tasks when the work queue is full. Commonly used rejection policies include AbortPolicy, DiscardPolicy, DiscardOldestPolicy and CallerRunsPolicy.

3. How to use Java thread pool

The method of using Java thread pool can be divided into three steps: thread pool initialization, task submission and thread pool closing.

1. Thread pool initialization:

Java thread pool initialization can use the factory method provided by the Executors class to create a thread pool, usually using ThreadPoolExecutor to create a thread pool object. The following code is an example of creating a thread pool:

ThreadPoolExecutor threadPool = new ThreadPoolExecutor(
  10,  // 核心线程数
  100,  // 最大线程数
  60,   // 空闲线程存活时间
  TimeUnit.SECONDS, // 存活时间单位
  new LinkedBlockingQueue<Runnable>(), // 队列大小
  Executors.defaultThreadFactory(),
  new ThreadPoolExecutor.AbortPolicy() // 拒绝策略
);

2. Task submission:

Task submission requires using the submit or execute method provided by the thread pool to submit the task to the work queue and wait. Thread pool processing. The following code is an example of submitting a task to the thread pool:

Future<String> future = threadPool.submit(new Callable<String>() {
  @Override
  public String call() throws Exception {
    return "Hello, World!";
  }
});

System.out.println(future.get()); // 输出Hello, World!

3. Thread pool closure:

When the thread pool is no longer needed, the thread pool should be closed to release resources. The following code is an example of closing the thread pool:

threadPool.shutdown();

4. Java thread pool application scenarios and optimization strategies

Java thread pool is suitable for scenarios that require a large amount of concurrent processing. Common application scenarios include:

1. Network communication: such as Web server, file server, etc.

2. Data processing: such as big data analysis, data mining, etc.

3. Game development: such as online games, mobile games, etc.

4. Real-time video processing: such as video calls, video monitoring, etc.

In order to optimize the performance of the Java thread pool, appropriate adjustments need to be made according to different application scenarios. The following are examples of several optimization strategies.

1. Reasonably adjust the thread pool configuration parameters.

Thread pool size, work queue size, maximum thread pool size, thread survival time and rejection policy will all affect the performance of the thread pool and need to be appropriately adjusted according to business needs.

2. Use an appropriate thread pool.

Java thread pool provides different types of thread pools, such as ExecutorService, FixedThreadPool, CahedThreadPool and SingleThreadExecutor. Different types of thread pools can be selected according to different business scenarios.

3. Use appropriate synchronization methods.

The synchronization methods used in the Java thread pool include synchronized, volatile, Lock and Atomic, etc. You need to choose the appropriate synchronization method according to the specific situation.

4. Avoid thread deadlock and starvation.

When developing and using the Java thread pool, it is necessary to avoid thread deadlock and starvation, avoid threads waiting and blocking for a long time, and optimize the efficiency of the thread pool.

Summary:

Java thread pool is an efficient concurrent programming technology that can make full use of CPU resources and improve the concurrent processing capabilities of the system. By properly configuring thread pool parameters, using appropriate thread pool and synchronization methods, and avoiding thread deadlock and starvation, the performance of the Java thread pool can be optimized and the efficiency and stability of the system can be improved.

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