CODEWITHSUNDEEP
javamultithreading
Sameek Mishra
Sameek Mishra

Reputation: 9384

Correct approach for creating Multithread in java?

I have a class,which implements Runnable interface. I want to create multiple threads for that class and I have found two approaches for creating a multithread:

  class MyRunnable implements Runnable {
        public void run() {
          System.out.println("Important job running in MyRunnable");
     }
   }

1.first approach:

    public class TestThreads {
    public static void main (String [] args) {
    MyRunnable r = new MyRunnable();
    Thread foo = new Thread(r);
    Thread bar = new Thread(r);
    Thread bat = new Thread(r);
    foo.start();
    bar.start();
    bat.start();
    }
    }

2.second approach:

public class TestThreads 
{
public static void main (String [] args) 
{
Thread[] worker=new Thread[3];
MyRunnable[] r = new MyRunnable[3];

for(int i=0;i<3;i++)
{
   r[i] = new MyRunnable();
   worker[i]=new Thread(r[i]);
   worker[i].start();

}
}
}

Which one is best approach to use and what is difference between both?

Regards

Upvotes: 1

Views: 5192

Answers (4)

Tudor
Tudor

Reputation: 62439

Well each one of the two approaches has their use:

  1. The first approach is useful if you have a few different tasks to execute in parallel that do not use the same Runnable interface (i.e. download a web page and in the mean time process some XML). Of course, this is not visible in your example, because you are using the same interface.
  2. The second approach is when you want to process the same thing with multiple threads (aka a master-slave pattern, where the master thread spawns a team of threads to process the same thing and then joins them at a barrier).

Upvotes: 0

Michael Wiles
Michael Wiles

Reputation: 21186

Only difference is the first one there is only one copy of "MyRunnable" that is run 3 times. 2nd approach each thread has its own copy of MyRunnable. Not a problem in this case as

Upvotes: 0

dmeister
dmeister

Reputation: 35604

In your example the runnable has not instance state, so you don't need multiple instances of it.

Otherwise I like the second approach more, because every time you cut&paste a line of codemultiple times in a row, a loop usually is the better idea.

And usually, you should wait for a thread you started. 

public class TestThreads {
    public static void main (String [] args) {
        Thread[] worker=new Thread[3];
        Runnable r = new MyRunnable();

        for(int i=0;i<3;i++) {
           worker[i]=new Thread(r);
           worker[i].start();
        }

         for(int i=0;i<3;i++) {
           worker[i].join();
           worker[i] = null;
        }
    }

}

The next step then would be using the ExecutorService of Java 5+. You don't want and need to manage you own thread in modern Java.

int poolSize = 3;
int jobCount = 3;
Runnable r = new MyRunnable()
ExecutorService  pool = Executors.newFixedThreadPool(poolSize);
for (int i = 0; i < jobCount; i++) {
    pool.execute(r);
}
pool.shutdown();

Upvotes: 2

tanyehzheng
tanyehzheng

Reputation: 2221

I would recommend you to use a ExecutorService. sample

Upvotes: 2

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