Java多线程中如何创建线程池

在Java中，可以使用java.util.concurrent.Executors类来创建线程池。以下是几种常见的线程池类型及其创建方法：

1. 固定大小的线程池（Fixed Thread Pool）：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class FixedThreadPoolExample {
    public static void main(String[] args) {
        int numberOfThreads = 5;
        ExecutorService executorService = Executors.newFixedThreadPool(numberOfThreads);

        for (int i = 0; i < 10; i++) {
            Runnable worker = new WorkerThread("" + i);
            executorService.execute(worker);
        }

        executorService.shutdown();
        while (!executorService.isTerminated()) {
        }
        System.out.println("Finished all threads");
    }
}

class WorkerThread implements Runnable {
    private String command;

    public WorkerThread(String s) {
        this.command = s;
    }

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + " Start. Command = " + command);
        processCommand();
        System.out.println(Thread.currentThread().getName() + " End.");
    }

    private void processCommand() {
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

2. 单线程的线程池（Single Thread Executor）：

ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();

3. 可缓存的线程池（Cached Thread Pool）：

ExecutorService cachedThreadPool = Executors.newCachedThreadPool();

4. 定时任务线程池（Scheduled Thread Pool）：

import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.Executors;

ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(5);

5. 单线程定时任务线程池（Single Thread Scheduled Executor）：

ScheduledExecutorService singleThreadScheduledExecutor = Executors.newSingleThreadScheduledExecutor();

创建线程池后，可以使用execute(Runnable)方法提交任务。当不再需要线程池时，应调用shutdown()方法来关闭线程池。如果需要等待所有已提交的任务完成，可以调用awaitTermination(long timeout, TimeUnit unit)方法。

注意：在实际应用中，应根据具体需求选择合适的线程池类型，并合理配置线程池参数，以达到最佳性能。