CODEWITHSUNDEEP
javamultithreadingjunit4
user3138008
user3138008

Reputation: 3

multi-thread run processes simultaneously

I am currently interested in learning about Multi-threading. I have written a piece of code. And my question is if this the correct way. I later want to implement this in another code of mine. My idea was to run multiple threads existing of the same class. So let's say 5 threads and they all have a runner class inside them. What I want to implement in another code, is that I want to run multiple browsers at once. So, I have a class Browser. And then I have 5 threads with the class Browser. And they are all working simultaneously but don't know each other, so they don't have any interaction with each other at all.

So is this idea OK then?

class Runner implements Runnable {
public void run() {
    for(int i = 0; i < 10; i++) {
        System.out.println(Thread.currentThread().getName() + " - " + i);

        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
}


public class BasisDemo {
    public static void main(String[] args) {
        Thread runner1 = new Thread(new Runner(), "Runner 1");
        runner1.start();

        Thread runner2 = new Thread(new Runner(), "Runner 2");
        runner2.start();
    }

}

Is this a good practise and does it support my idea?

Or is using multi-threading even unnecessary. I don't know it for sure.

Thanks for helping me out.

Upvotes: 0

Views: 777

Answers (3)

Basil Bourque
Basil Bourque

Reputation: 338406

1 Thread, not 5

Or is using multi-threading even unnecessary. I don't know it for sure.

If using the same class to do the same work, then No, no need for 5 threads. You only need one thread to run a task daily in the background.

If you want a copy everyday of a daily newspaper, would you send one of you children to the store with a dollar in hand each morning or would you send five of your children each with a dollar in hand?

ScheduledExecutorService

Also, Java provide a slick facility for this kind of work where you are scheduling tasks to be done in the background regularly: ScheduledExecutorService. Search Stack Overflow for more info, and read the Oracle Tutorial on Executors.

Upvotes: 0

Junbang Huang
Junbang Huang

Reputation: 1967

So your idea would work. If you try this code below.

System.out.println(System.currentTimeMillis());
System.out.println(System.currentTimeMillis());

You will find that the time is actually the same, which mean these two lines are executed almost at the same time.

In term of your code:

Thread runner1 = new Thread(new Runner(), "Runner 1");
runner1.start();

Thread runner2 = new Thread(new Runner(), "Runner 2");
runner2.start();

These threads will be executed at almost the same time, that's why your idea will work.

To make it more accurate. You can switch your codes:

Thread runner1 = new Thread(new Runner(), "Runner 1");
Thread runner2 = new Thread(new Runner(), "Runner 2");
runner1.start();
runner2.start();

If you want to make the timing even more accurate. You can use CyclicBarrier. It allows a set of thread to wait for each other and start at the same time. Here is demo codes:

class Demo {
   final CyclicBarrier barrier;

   class Broswer implements Runnable {
     Worker() { }
     public void run() {
       while (!done()) {
         try {
           // wait for other threads
           barrier.await();
           // work for something, in your case an hour, but how can you control that
           // work....
           // sleep for a certain time
           sleep(certain time)
         } catch (InterruptedException ex) {
           return;
         } catch (BrokenBarrierException ex) {
           return;
         }
       }
     }
   }

   public static main(String args[]) {
     barrier = new CyclicBarrier(N);
     for (int i = 0; i < N; ++i)
       new Thread(new Broswer()).start();

     // wait until all done, in your case, forever.
   }
 }

Upvotes: 1

benssky
benssky

Reputation: 1

Sounds like you're on the right track. Each thread will have no reference of each other, since you defined them as separate objects. They would both be able to contain their own data, execute their own methods, completely independently of one another.

One way you could confirm they are executing simultaneously is to make your loop start from a random number, that way you will see the console output incrementing beginning from two different numbers. (i.e. 100, 50, 101, 102, 51, 52, ...)

What you have outlined is the most common way to create threads in Java, you can read more about it here if you have questions later on.

Upvotes: 0

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