Java - 使用 For 循环创建多个线程

Java - Creating Multiple Threads with a For Loop

提问by HSeldon

I am trying to create multiple threads, the number of which is dependent on the input from the command line. I know extending Thread isn't the best OO practice unless you are making a specialized version of Thread, but hypothetically is this code creating the desired result?

我正在尝试创建多个线程，其数量取决于命令行的输入。我知道扩展 Thread 不是最好的 OO 实践，除非您正在制作 Thread 的专门版本，但假设这段代码创建了所需的结果？

class MyThread extends Thread { 

  public MyThread (String s) { 
    super(s); 
  }

  public void run() { 
    System.out.println("Run: "+ getName()); 
  } 
}


 class TestThread {
  public static void main (String arg[]) { 

    Scanner input = new Scanner(System.in);
    System.out.println("Please input the number of Threads you want to create: ");
    int n = input.nextInt();
    System.out.println("You selected " + n + " Threads");

    for (int x=0; x<n; x++)
    {
        MyThread temp= new MyThread("Thread #" + x);
        temp.start();
        System.out.println("Started Thread:" + x);
    }
}
}

采纳答案by Daniel Hershcovich

Yes, it is creating and starting nthreads, all ending immediately after printing Run:and their name.

是的，它正在创建和启动n线程，所有线程都在打印Run:和它们的名称后立即结束。

回答by Er. Joshi

One important thing java JVM can create 20000 thread at a time . Creating 255 threads in java

java JVM 一次可以创建 20000 个线程的一件重要事情。在 Java 中创建 255 个线程

class MyThread1 extends Thread {
    int k;
    public MyThread1(int i) {
            k = i;
    }

    @Override
    public void run() {
        //Your Code
        System.out.println("Thread no. "+k);

    }
}
class MainClass {

    public static void main(String arg[]) throws UnknownHostException {
        Refresh() ;
    }

    public static void Refresh(){

        //create 255 Thread using for loop
        for (int x = 0; x < 256; x++) {
            // Create Thread class 
            MyThread1 temp = new MyThread1(x);
                temp.start();
            try {
                temp.join(10);
            }
            catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

回答by Ravindra babu

You have better alternative with ExecutorService

ExecutorService有更好的选择

Sample code:

示例代码：

import java.util.concurrent.*;

public class ExecutorTest{
    public static void main(String args[]){

        int numberOfTasks = Integer.parseInt(args[0]);
        ExecutorService executor= Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
        try{
            for ( int i=0; i < numberOfTasks; i++){
                executor.execute(new MyRunnable(i));                
            }
        }catch(Exception err){
            err.printStackTrace();
        }
        executor.shutdown(); // once you are done with ExecutorService
    }   
}
class MyRunnable implements Runnable{
    int id;
    public MyRunnable(int i){
        this.id = i;
    }
    public void run(){
        try{
            System.out.println("Runnable started id:"+id);
            System.out.println("Run: "+ Thread.currentThread().getName()); 
            System.out.println("Runnable ended id:"+id);
        }catch(Exception err){
            err.printStackTrace();
        }
    }
}

Usage:

用法：

java ExecutorTest 2

Runnable started id:0
Run: pool-1-thread-1
Runnable ended id:0
Runnable started id:1
Run: pool-1-thread-2
Runnable ended id:1

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