Thread Basics

Thread Basics

1-      Thread Creation :

There are two ways of creating a new thread.

Way-1 Implementing Runnable Interface:

public class CustRunnable implements Runnable {

    public void run() {

        System.out.println("Executed !");

    }

    public static void main(String args[]) {

        Thread myThread =  new Thread(new CustRunnable());

        myThread.start()

    }

}

Way-2 Extending Thread Interface:

public class CustThread extends Thread {

    public void run() {

        System.out.println("Executed from a new thread!");

    }

    public static void main(String args[]) {

        CustThread myThread = new CustThread();

        myThread.start();

    }

}

First way is preferable. Because it leaves the flexibility of extending another class and compatible with higher level thread management APIs.

2 -      Important Thread Methods

-    public static void sleep(long millis) throws InterruptedException

public static void sleep(long millis, int nanos) throws    InterruptedException

Executing threads goes to sleep for specified times amount. Puts thread into TIMED_WAITING state. Thread doesn’t leave locks it obtains. If thread is interrupted during sleep, InterruptedException is raised.

-          public void interrupt()

Used to interrupt a thread. When a thread is interrupted it stops what it is doing and does some thing in respose to interrupt.

Generally threads respond to interrupts by stopping execution. A typical respond is as in the example.

public void run() {

        try {

            Thread.sleep(10000);

        } catch (InterruptedException e) {

            return;// stop execution

        }

      }

Thread related methods tend to throw InterruptedException. If a thread is not invoking a method that throws InterruptedException, a thread my check interrupt status by calling Thread.interrupted()method.

·         Remember after throwing InterruptedException or returning true to static Thread.interrupted() method, thread’s internal interrupt status flag is cleared.

·         The non-static version of interrupted() method doesn’t clear interrupt status flag.

-          public final void join() throws InterruptedException

public final void join(long millis) throws InterruptedException

public final void join(long millis,int nanos) throws InterruptedException

Allows a thread to pause execution until another thread finishes execution. Puts  thread into WAITING state. Overloaded versions allows to specfy a timeout value and puts thread into  TIMED_WAITING state.

May throw InterruptedException .