Worker Thread in Java

Question

I need to read the data from a table every minute through thread & then perform certain action.

Should I just start a thread & put it in sleep mode for 1 minute

Answer 1

"Should I just start a thread & put it in sleep mode for 1 minute" Even if you want you want to go with traditional thread ( dont want to use executor Fremework) DO NOT USE SLEEP for waiting purpose as it will not release lock and its a blocking operation . DO USE wait(timeout) here.

Wrong Approach -

public synchronized void doSomething(long time)  throws InterruptedException {
  // ...
  Thread.sleep(time);
}

Correct Approach

public synchronized void doSomething(long timeout) throws InterruptedException {
// ...
  while (<condition does not hold>) {
    wait(timeout); // Immediately releases the current monitor
  }
}

you may want to check link https://www.securecoding.cert.org/confluence/display/java/LCK09-J.+Do+not+perform+operations+that+can+block+while+holding+a+lock

Answer 2

As so often, the Java 5 extensions from the java.util.concurrent package are a huge help here.

You should use the ScheduledThreadPoolExecutor. Here is a small (untestet) example:

class ToSomethingRunnable implements Runnable {
    void run() {
        // Add your customized code here to update the contents in the database.
    }
}

ScheduledThreadPoolExecutor executor = Executors.newScheduledThreadPool(1);
ScheduledFuture<?> future = executor.scheduleAtFixedRate(new ToSomethingRunnable(), 
     0, 1, TimeUnit.MINUTES); 

// at some point at the end
future.cancel();
executor.shutdown();

Update:

A benefit of using an Executor is you can add many repeating tasks of various intervals all sharing the same threadpool an the simple, but controlled shutdown.

Answer 3

An alternative to create a thread yourself is to use the ExcecutorService, where Executors.newScheduledThreadPool( 1 ) creates a thred pool of size 1 and scheduleAtFixedRate has the signature: scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit);

public class ScheduledDBPoll
{
  public static void main( String[] args )
  {
    ScheduledExecutorService scheduler = Executors.newScheduledThreadPool( 1 );
    ScheduledFuture<?> sf = scheduler.scheduleAtFixedRate(
        new Runnable() {
          public void run() {
            pollDB();
          }
        },
        1,  60,TimeUnit.SECONDS );
  }
}

Answer 4

Your approach is good.You can proceed your approach.

This Sample will help you to do your task:

class SimpleThread extends Thread {
   public SimpleThread(String str) {
    super(str);
   }
   public void run() {
    for (int i = 0; i < 10; i++) {
        System.out.println(i + " " + getName());
        try {
             // Add your customized code here to update the contents in the database.

            sleep((int)(Math.random() * 1000));

        } catch (InterruptedException e) {}
    }
    System.out.println("DONE! " + getName());
}
}