Process Jobs from a list with Java Threads

Question

I have a program which has to process a list with many jobs. To speed up the whole things, I would like to implement Threads.

I think about something like this:

Main-Class

// I have a joblist with 100 entries
int iAmountThreads = 5;
for(Job oJob : joblist)
{
//only execute 5 Jobs at the same time
        if(Thread.activeCount() < iAmountThreads)
        {
            Runnable threadJob = new JobRunnable(oJob);
            Thread myThread = new Thread(threadJob);
            myThread.start();
        }
    }

//wait here until all jobs from the joblist are finished

Runnable Class Implementing Runnable

public class JobRunnable implements Runnable
{
     private Job oJob;

     public JobRunnable(Job _oJob)
     {
         oJob = _oJob;

     }

     public void run() 
     {
        //processing of the job
     }
}

I'm looking for a way to run 5 Jobs at the same time until the whole list is processed. When one Job is finished -> the next Thread shall start.

Thanks for any help!

Answer 1

Use a fixed thread pool, via the executor API:

Executor executor = Executors.newFixedThreadPool(5);

// all jobs are submitted sequentially, but only 5 jobs execute concurrently at a time
for(Runnable job : jobs)
{
    executor.execute(job);
}