multithreading in java

Question

I want "runnable" to run at 5tps. This is not executing paralelly.

package tt;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

public class mySpawner {

public int tillDone = 0;
public int tillMax = 0;
public ArrayList arrayList;
private myWorker myworking;
private ScheduledExecutorService service = Executors.newScheduledThreadPool(50);

Runnable runnable = new Runnable() {

    @Override
    public void run() {
        try {
            System.out.println(System.nanoTime());
            Thread.sleep(7000);
        } catch (InterruptedException ex) {
            Logger.getLogger(mySpawner.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
};


public void activate() {
    try {
        service = Executors.newScheduledThreadPool(50);
        service.scheduleAtFixedRate(runnable, 0, 200, TimeUnit.MILLISECONDS);
    } catch (Exception e) {//Catch exception if any
        System.err.println("Error: " + e.getMessage());
    }

}

public void deactivate() {
    service.shutdown();
}

}

Answer 1

Consider this:

• Your tasks are sleeping for 7 seconds during their execution
• You are scheduling a new task every 200ms
• You only have 50 threads in your executor

It should be clear, I hope, that you'll run out of pooled threads in just a few seconds, and you'll lose your parallelism. You need to balance this better, either by reducing the rate or reducing the sleep. Increasing the pool size won't help, you'll still run out of threads.