How to implement executor service by passing new thread as parameter to execute?

Question

I needed to refactor a code to see if it can help me resolve my "Could not open Hibernate Session for transaction". I am currently trying to streamline the way threads are handled in the code.

The existing code is seen as below. Lets call it 'code A':

    if (!CollectionUtils.isEmpty(dailyReportProjectList)) {
            for (ProjectEntity project : dailyReportProjectList) {
                Thread.sleep(2000);
                new Thread(() -> {
                    try {
                        // Implementation Logic

                        if (isConfig == true) {
                            // Generating Daily Report
                        
                            if (dailyRep != null) {
                                LOG.info(
                                        "============start of daily report mail for zone : " + zone + ", newZone : "
                                                + newZone + " for date : " + currOrPrevDay + "===============");
                                new Thread(() -> {
                                    try {
                                        //genericController;
                                        
                                    } catch (Exception e) {
                                        e.printStackTrace();
                                        
                                        }
                                    }
                                }).start();
                            }
                        } else {
                                 //"All 4 default reports for site : " + project.getId() + ", empId:" + project.getEmployerId());
                            
                                }
                            }
                        }
                        LOG.info("End of generateReportByZone >> zone : " + zone);
                    } catch (Exception e2) {
                        e2.printStackTrace();
                        }
                    }
                }).start();
            }
        }

In order to streamline this I decided to proceed with Executor Service. I referred a few examples and I am confused as to use service.submit() or service.execute(). I am not seeing my intented benefit from the below code. Can you please help me identify any issues with this apporach.

EDIT: Based on the comments, I have simplified the existing code as above. There is a thread called inside the thread which I feel is not achieving much. Is this ok to have such implementation.

I am planning to do the following:

Instead of passing thread, as a parameter in the for loop, make a separate class and have it implement runnable.

  public class ReportProcessor implements Runnable {
  private int id;
  public ReportProcessor (int id){
   this.id = id;
   }

   public void run(){
   try {
  String currOrPrevDay = new String();
  ...// write the code in the try element of 'code A' here onwards

In the 'code A' executor. submit the newly created class

             for (i = 0; i < dailyReportProjectList.length; i ++){
         service.submit(new ReportProcessor(i));

         }

But how do I fulfil the dependencies required by the existing stated 'code A' if I separate out the logic to a new class. I am trying to model my executor service on the basis of this tutorial https://www.youtube.com/watch?v=KUdro0G1BV4&t=325s

user_4432328 · Answer

Do not pass a Thread, pass a lambda or anything "runnable".

        ExecutorService service = Executors.newFixedThreadPool(3);

        for (int i = 0; i < 10; i++) {
            final int number = i;
            service.execute(() -> System.out.println("test" + number));
        }

Edit:
I really think this code need simplicity. It seems you want to create reports.
So why create a thread in a Thread ?
And why Thread.sleep ? (generally malpractice, prefer wait/notify)

I do really think you don't need threads at all.
But if you really want (or need) them, loose coupling:

Each thread make a single, precise task.
Tests to decide what to do have to be upstream.

And try Streams and functional interfaces. It will simplify your code.

dailyReportProjectList.parallelStream()
    .filter(condition)
    .forEach(doSomething)

Streams manage threading themselves.

How to implement executor service by passing new thread as parameter to execute?

1 Answers