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Process tasks from a list using Java streams

I have a program that needs to process a list with many tasks. To speed things up, I would like to implement Threads.

I am thinking of 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 Implementation Runnable

public class JobRunnable implements Runnable
{
     private Job oJob;

     public JobRunnable(Job _oJob)
     {
         oJob = _oJob;

     }

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

I am looking for a way to run 5 Jobs at the same time until the entire list is processed. When one job is complete → the next thread will start.

Thanks for any help!

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3 answers


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);
}
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The easiest way is to use Java 8 parallel streams. Simple implementation:

List<JobRunnable> tasks = ...;
tasks.parallelStream()
    forEach(JobRunnable::run);


This can be changed and you don't need to use Runnable

; you can use any method from any class. You have to be careful with thread safety, but don't share state between objects in the list.

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You must use Executors.newFixedThreadPool(5)

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