Question

Using the concepts from the Concurrency Basics Tutorial I provided in Modules, write a program that consists of two threads. The first is the main thread that every Java application has. The main thread should create a new thread from the Runnable object, MessageLoop, and wait for it to finish. If the MessageLoop thread takes too long to finish, the main thread should interrupt it. Use a variable named maxWaitTime to store the maximum number of seconds to wait. The main thread should output a message stating that it is still waiting every half second. The MessageLoop thread should print out a series of 4 messages. These messages should be numbered, as in the example below. It should wait 850 milliseconds between printing messages to create a delay. If it is interrupted before it has printed all its messages, the MessageLoop thread should print "Message loop interrupted" and exit. Or you can let main print "Message loop interrupted". Your program must demonstrate that it can both output messages and interrupt the message output. To do this, place the body of main into a for loop using maxWaitTime as the index. As in the following example, it should finally output all 4 messages in the last iteration. So in main your code will be for (int maxWaitTime = 1; maxWaitTime <= 4; maxWaitTime++) { // All of main's processing goes here (Note that it does not say some, it says all). }

Sample output :

maxWaitTime: 1 second(s)
main : Starting MessageLoop thread
main : Waiting for MessageLoop thread to finish
main : Continuing to wait...
main : Continuing to wait...
Thread-0 : 1. All that is gold does not glitter, Not all those who wander are lost
main : MessageLoop interrupted
maxWaitTime: 2 second(s)
main : Starting MessageLoop thread
main : Waiting for MessageLoop thread to finish
main : Continuing to wait...
main : Continuing to wait...
Thread-1 : 1. All that is gold does not glitter, Not all those who wander are lost
main : Continuing to wait...
main : Continuing to wait...
Thread-1 : 2. The old that is strong does not wither, Deep roots are not reached by the frost
main : MessageLoop interrupted
maxWaitTime: 3 second(s)
main : Starting MessageLoop thread
main : Waiting for MessageLoop thread to finish
main : Continuing to wait...
main : Continuing to wait...
Thread-2 : 1. All that is gold does not glitter, Not all those who wander are lost
main : Continuing to wait...
main : Continuing to wait...
Thread-2 : 2. The old that is strong does not wither, Deep roots are not reached by the frost
main : Continuing to wait...
main : Continuing to wait...
Thread-2 : 3. From the ashes a fire shall be woken, A light from the shadows shall spring
main : MessageLoop interrupted
maxWaitTime: 4 second(s)
main : Starting MessageLoop thread
main : Waiting for MessageLoop thread to finish
main : Continuing to wait...
main : Continuing to wait...
Thread-3 : 1. All that is gold does not glitter, Not all those who wander are lost
main : Continuing to wait...
main : Continuing to wait...
Thread-3 : 2. The old that is strong does not wither, Deep roots are not reached by the frost
main : Continuing to wait...
main : Continuing to wait...
Thread-3 : 3. From the ashes a fire shall be woken, A light from the shadows shall spring
main : Continuing to wait...
Thread-3 : 4. Renewed shall be blade that was broken
main : Done!

Your class must be in a package named mypackage and be named Concurrency, as explained in last week's videos. It should be contained in 1 and only 1 source file. Must be in Java and result info as above.

Answer 1

Case: When thread interrupts:

Code -

package thread;

public class MessageLoop implements Runnable {

public void run() {

try {

for(int i=1;i<=5;i++){

Thread.sleep(2100);

System.out.println("Thread-0: Message "+(i));

}

}

catch (InterruptedException ex) {

System.out.println("Thread-0: Message loop interrupted");

}

}

public static void main(String[] args) {

System.out.println("main: Starting MessageLoop thread");

//create a thread

Thread t1 = new Thread(new MessageLoop());

//start the thread

t1.start();

System.out.println("main: Waiting for MessageLoop thread to finish");

//until thread alive

while(t1.isAlive()){

try {

//1 second delay and print message

System.out.println("main: Continuing to wait...");

System.out.println("main: Interrupting");

t1.interrupt();

Thread.sleep(1000);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

System.out.println("main: Finished!");

}

}

Output of the code:

Case II -

package thread;

public class MessageLoop implements Runnable {

public void run() {

try {

for(int i=1;i<=5;i++){

Thread.sleep(2100);

System.out.println("Thread-0: Message "+(i));

}

}

catch (InterruptedException ex) {

System.out.println("Thread-0: Message loop interrupted");

}

}

public static void main(String[] args) {

System.out.println("main: Starting MessageLoop thread");

//create a thread

Thread t1 = new Thread(new MessageLoop());

//start the thread

t1.start();

System.out.println("main: Waiting for MessageLoop thread to finish");

//until thread alive

while(t1.isAlive()){

try {

//1 second delay and print message

System.out.println("main: Continuing to wait...");

Thread.sleep(1000);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

System.out.println("main: Finished!");

}

}