The content of this article is about how to use the Executor multi-threading framework (with examples). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
In our JDK1.5, JAVA launched a framework (Executor) encapsulated for more convenient development of multi-threaded applications. Compared with the traditional Thread class, Executor is more convenient, has better performance, and is more convenient. Easy to manage and supports thread pools. Generally, when developing a crawler, in order to improve the efficiency of the crawler, multi-threading is required, and Executor is a very good choice.
Common interfaces:
1) Create a thread pool with a fixed number of threads:
public static ExecutorService newFixedThreadPool(int nThreads)
2) Execute a thread
void java.util.concurrent.Executor.execute(Runnable command)
3) View the current number of active threads
int java.util.concurrent.ThreadPoolExecutor.getActiveCount ()
4) End all threads
void java.util.concrrent.ExecutorService.shutdonw()
Executor will be effective when managing multiple threads s arrangement. Processing, for example, when there are 10 threads in the thread pool when it is created, adding more than 10 Executors to implement threads will perform effective queue blocking and scheduling. For us developers, this is transparent and there is no need to care about how it operates internally.
Example code:
package com.java.executor; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.ThreadPoolExecutor; public class ExecutorTest { private static Integer count = 1; //数量 private static boolean flag = true;//是否执行 public static void main(String[] args) { ExecutorService executorService = Executors.newFixedThreadPool(10);//在连接池中初始化10个线程 while(flag){ if(count<=100){ executorService.execute(new Runnable() { @Override public void run() { System.out.println("执行 ： " + count++); } }); }else{ //判断是否有活动线程 if(((ThreadPoolExecutor)executorService).getActiveCount()==0){ executorService.shutdown();//结束所有线程 flag=false; System.out.println("完成操作"); } } try { Thread.sleep(100);//休息0.1秒 } catch (InterruptedException e) { e.printStackTrace(); } } } }
This is a simple way to use Executor, convenient and fast, and easy to learn. Why do we need to take a break here 0.1 In terms of seconds, we do not lock the above code. If we do not rest on this code until the count is greater than 100, the thread will still be active, which will cause the thread to not be closed. In addition, the thread execution speed is very fast. It will exceed our needs, and it is easy to block the IP when the crawler crawls the web using such a speed.
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