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📜  Java多线程-线程池

📅  最后修改于: 2020-09-27 01:22:42             🧑  作者: Mango

Java线程池

Java线程池表示一组正在等待作业并多次重复使用的工作线程。

对于线程池，将创建一组固定大小的线程。服务提供商从线程池中拉出一个线程并为其分配作业。作业完成后，线程再次包含在线程池中。

Java线程池的优势

更好的性能由于不需要创建新线程，因此可以节省时间。

实时使用

它用于Servlet和JSP，其中容器创建一个线程池来处理请求。

Java线程池示例

让我们看一个使用ExecutorService和Executors的Java线程池的简单示例。

文件：WorkerThread.java

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
class WorkerThread implements Runnable {
    private String message;
    public WorkerThread(String s){
        this.message=s;
    }
     public void run() {
        System.out.println(Thread.currentThread().getName()+" (Start) message = "+message);
        processmessage();//call processmessage method that sleeps the thread for 2 seconds
        System.out.println(Thread.currentThread().getName()+" (End)");//prints thread name
    }
    private void processmessage() {
        try {  Thread.sleep(2000);  } catch (InterruptedException e) { e.printStackTrace(); }
    }
}

文件：JavaThreadPoolExample.java

public class TestThreadPool {
     public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(5);//creating a pool of 5 threads
        for (int i = 0; i < 10; i++) {
            Runnable worker = new WorkerThread("" + i);
            executor.execute(worker);//calling execute method of ExecutorService
          }
        executor.shutdown();
        while (!executor.isTerminated()) {   }

        System.out.println("Finished all threads");
    }
 }

输出：

pool-1-thread-1 (Start) message = 0
pool-1-thread-2 (Start) message = 1
pool-1-thread-3 (Start) message = 2
pool-1-thread-5 (Start) message = 4
pool-1-thread-4 (Start) message = 3
pool-1-thread-2 (End)
pool-1-thread-2 (Start) message = 5
pool-1-thread-1 (End)
pool-1-thread-1 (Start) message = 6
pool-1-thread-3 (End)
pool-1-thread-3 (Start) message = 7
pool-1-thread-4 (End)
pool-1-thread-4 (Start) message = 8
pool-1-thread-5 (End)
pool-1-thread-5 (Start) message = 9
pool-1-thread-2 (End)
pool-1-thread-1 (End)
pool-1-thread-4 (End)
pool-1-thread-3 (End)
pool-1-thread-5 (End)
Finished all threads