Using isAlive() and join() method in java

 how to use isAlive() and Join( ):

Using isAlive( ) and join( )

As mentioned, often you will want the main thread to finish last.Two ways exist to determine whether a thread has finished.

•   isAlive()
• join()

isAlive():

you can call isAlive( ) on the thread. This method is defined by Thread.

  General form of isAlive()

final boolean isAlive( )

The isAlive( )method returns true if the thread upon which it is called is still running. It returns false otherwise.

join():

While isAlive( ) is occasionally useful, the method that you will more commonly use to wait for a thread to finish is called join( ).

general form of join()

final void join( ) throws InterruptedException

This method waits until the thread on which it is called terminates. Its name comes from the concept of the calling thread waiting until the specified thread joinsit. Additional forms of join( ) allow you to specify a maximum amount of time that you want to wait for the specified thread to terminate.

Example:using isAlive() and join()

// Using join() to wait for threads to finish.

class NewThread implements Runnable 

{

String name; // name of thread

Thread t;

NewThread(String threadname) {

name = threadname;

t = new Thread(this, name);

System.out.println("New thread: " + t);

t.start(); // Start the thread

}

// This is the entry point for thread.

public void run() 

{

try 

{

for(int i = 5; i > 0; i--)

 {

System.out.println(name + ": " + i);

Thread.sleep(1000);

}

} catch (InterruptedException e) {

System.out.println(name + " interrupted.");

}

System.out.println(name + " exiting.");

}

}

class DemoJoin

 {

public static void main(String args[])

 {

NewThread ob1 = new NewThread("One");

NewThread ob2 = new NewThread("Two");

NewThread ob3 = new NewThread("Three");

System.out.println("Thread One is alive: "+ ob1.t.isAlive());

System.out.println("Thread Two is alive: "+ ob2.t.isAlive());

System.out.println("Thread Three is alive: "+ ob3.t.isAlive());

// wait for threads to finish

try

 {

System.out.println("Waiting for threads to finish.");

ob1.t.join();

ob2.t.join();

ob3.t.join();

} 

catch (InterruptedException e)

 {

System.out.println("Main thread Interrupted");

}

System.out.println("Thread One is alive: "+ ob1.t.isAlive());

System.out.println("Thread Two is alive: "+ ob2.t.isAlive());

System.out.println("Thread Three is alive: "+ ob3.t.isAlive());

System.out.println("Main thread exiting.");

}

}

Sample output from this program is shown here. (Your output may vary based on processor speed and task load.)

New thread: Thread[One,5,main]
New thread: Thread[Two,5,main]
New thread: Thread[Three,5,main]
Thread One is alive: true
Thread Two is alive: true
Thread Three is alive: true
Waiting for threads to finish.
One: 5
Two: 5
Three: 5
One: 4
Two: 4
Three: 4
One: 3
Two: 3
Three: 3
One: 2
Two: 2

Three: 2