Java - Close a thread with 'return' not working

Question

I have the following code in a class which contains my main method

ExecutorService executor = Executors.newFixedThreadPool(1);
Runnable formatConcentration = new formatConcentration(87);
executor.execute(formatConcentration);
System.out.println("Called an instance of formatConcentration");
while (!executor.isTerminated())
{
    //stay Alive
    Thread.sleep(1000);
    System.out.println("Still alive");
}
System.out.println("Program successfully finished");
return;

This creates an instance of formatConcentration class. The code for which is the following (I've taken all of my functionality out for the sake of the example).

public class formatConcentration extends Thread{
    private int numberOfNewRows;

    formatConcentration(int rows)
    {
        this.numberOfNewRows = rows;
    }
    public void run() {

        System.out.println("Running the Formatting Script");
        final int numberOfNewRegistered = this.numberOfNewRows;
        try 
        {
            System.out.println("Finished formatting");
        }//end of try
        catch (Exception e1) 
        {
            log.log(e1.toString());
            log.closeLog() ;
            System.exit(1) ;
        }
        System.out.println("Still Finished formatting");
        return;
    }
}

My problem is that once return is invoked it does not terminate the thread.

I have done quite a lot of looking around and as far as I can tell this should be fine but I would imagine that I'm overlooking something small and would appreciate fresh eyes on the problem.

Or if someone has a suggestion of how to kill the thread from inside the run(){} method I would greatly appreciate it (preferably not by setting a variable that I'll check in the main class but if that's how I have to do it so be it) as I know that once it reaches the return statement it's finished and no longer need any reference to variables created in run().

The output generated to the console is as follows:

Called an instance of formatConcentration
Running the Formatting Script
Finished formatting
Still Finished formatting
Still alive
Still alive
Still alive
Still alive
Still alive
etc.

Answer 1

ExecutorService executor = Executors.newFixedThreadPool(1);
Runnable formatConcentration = new formatConcentration(87);
executor.execute(formatConcentration);
System.out.println("Called an instance of formatConcentration");
executor.shutdown();
while (!executor.isTerminated())
{
    //stay Alive
    Thread.sleep(1000);
    System.out.println("Still alive");
}
System.out.println("Program successfully finished");
return;

Another simpler way to do it would be :

   ExecutorService executor = Executors.newFixedThreadPool(1);
    Runnable formatConcentration = new formatConcentration(87);
    executor.execute(formatConcentration);
    executor.shutdown();
    try {
        executor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

Executor awaitTermination method substitutes your loop.