Java - Creating Multiple Threads with a For Loop

Question

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?

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);
    }
}
}

Answer 1

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

Answer 2

You have better alternative with ExecutorService

Sample code:

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:

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 

Related posts: ( Advantages of using ExecutorService as a replacement for plain Thread)

ExecutorService vs Casual Thread Spawner

How to properly use Java Executor?

Answer 3

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

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();
            }
        }
    }
}