How to design a thread pool for concurrency and multi-threading of Java functions?

When creating a thread pool, you should consider the number of core threads, maximum number of threads, queues, and rejection policies. Thread pools in Java can be implemented through the Executors class, for example using the newFixedThreadPool() method. To optimize performance, you can adjust the number of threads, queue size, use custom deny policies, and monitor metrics.

Concurrency and multithreading of Java functions: How to design a thread pool

Introduction

Thread pools are crucial in multi-threaded programming because they help manage the life cycle of threads and improve code efficiency and scalability. This article guides you through designing and implementing a thread pool through Java functions.

Thread pool design

When creating a thread pool, you need to consider the following key factors:

• Number of core threads: This is the number of threads in the pool that are always active.
• Maximum number of threads: This is the maximum number of active threads allowed in the pool.
• Queue: This is a queue used to store tasks waiting to be executed.
• Rejection Policy: When the thread pool is full, it will decide how to handle new tasks.

Code Example

The following code example shows how to create a thread pool using the Executors class:

// 创建一个有 5 个核心线程和 10 个最大线程的线程池
ExecutorService pool = Executors.newFixedThreadPool(5, 10);

// 向池中提交一个任务
pool.submit(() -> {
    System.out.println("任务正在执行");
});

// 关闭线程池
pool.shutdown();

Practical Case

Suppose you have an application that needs to handle a large number of small tasks. By using a thread pool, you can process these tasks in parallel, significantly improving the performance of your application.

The following is another example of setting up a thread pool:

// 使用队列来存储等待的任务
BlockingQueue<Runnable> tasks = new ArrayBlockingQueue<>(100);

// 创建一个自定义线程工厂
ThreadFactory threadFactory = new ThreadFactory() {
    @Override
    public Thread newThread(Runnable r) {
        return new Thread(r, "任务线程");
    }
};

// 创建一个自定义拒绝策略
RejectedExecutionHandler rejectionHandler = new RejectedExecutionHandler() {
    @Override
    public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
        System.out.println("任务被拒绝：" + r.toString());
    }
};

// 创建一个自定义线程池
ThreadPoolExecutor pool = new ThreadPoolExecutor(
    5, 10, 0L, TimeUnit.MILLISECONDS,
    tasks, threadFactory, rejectionHandler
);

// 向池中提交任务
for (int i = 0; i < 100; i++) {
    pool.submit(() -> {
        System.out.println("任务 " + i + " 正在执行");
    });
}

// 关闭线程池
pool.shutdown();

Optimizing the thread pool

To optimize thread pool performance, consider the following tips:

• Adjust the number of core threads and maximum threads to match your application load.
• Use reasonable queue size.
• Use a custom deny policy to handle tasks that cannot be processed.
• Monitor thread pool metrics to detect performance issues.

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