Executor框架与Thread

Executor将线程的创建和线程的执行解耦，比较下面两个例子：

1：TaskExecutionWebServer.java

package chapter06;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

public class TaskExecutionWebServer {
    private static final int NTHREADS=100;
    private static final Executor exec = Executors.newFixedThreadPool(NTHREADS);

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(100);

        while (true) {
            final Socket connection=serverSocket.accept();
            Runnable task=new Runnable() {  //Runnable 不处理异常，callable 处理异常。
                @Override
                public void run() {
                    //handlerRequest (connection);
                }
            };

            exec.execute(task);  //将Runnable 交给executor
        }
    }
}

2：ThreadPerTaskWebServer ,不可取。

package chapter06;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @program: GradleTestUseSubModule
 * @author: Yafei Li
 * @create: 2018-07-13 21:05
 **/
public class ThreadPerTaskWebServer {
    public static void main(String[] args) throws IOException {
        ServerSocket socket = new ServerSocket(80);
        while (true) {
            final Socket connection=socket.accept();
            Runnable task=new Runnable() {
                @Override
                public void run() {
//                    handleRequest(connection);
                }
            };
            new Thread(task).start();
        }
    }
}

从上面两个例子可以看出  Executors 会创建线程池，从线程池中取出线程执行任务。可以控制线程的数量。

而Thread要为每个任务创建一个线程，浪费资源。  开销比较高。

所以Executors  能够将创建线程与任务执行解耦，  控制线程数量等优点。

当遇到new  Thread(Runnable).start();  时，应该换为Executor.execute(Runnable);