Assignment 3 – Multithread Programming

COMP 3411: Operating Systems 1
Assignment 3 – Multithread Programming (9%)
Introduction
Assignment 3 total is 10 marks. You should begin Assignment 3 in Module 4; it is
due at the end of Module 4. Check your Course Schedule for the precise due date.
Directions for submitting Assignment 3 to your Open Learning Faculty Member for
grading can be found in the Assignments Overview tab. An assignment marking
criteria follows at the end of this document.
Instructions
Through this assignment you will learn how to use multiple threads in your Java
application programs. This assignment is to write a multithread Java program that
performs matrix multiplication. In your program there should be two operand
matrices and a results matrix. The two operand matrices should be populated with
sample data. You will need to calculate each element in the result matrix using a
separate thread. The sizes of three matrices should be stored in static variables. The
contents of the two operand matrices and the result matrix should be printed by
your program.
You must submit Java files and screen shots that show how your program
works. Refer to the marking criteria at the end of this document.
Thread and Runnable classes
The following five sections are prepared to help you understand how to use Thread
and Runnable classes to implement multithread Java application programs.
1. Java thread states
ne
w
runnable
blocked
terminated
start()
sleep()
I/O
I/O is
available
exit()
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2. Two approaches:
2.1 extends Thread
class Worker extends Thread
{
int id; // not shared among threads; instance variable for an
object, i.e., thread
Worker (int id) {
this.id = id;
}
// need to be implemented; starting point of threads, when
start() is called
public void run() {
System.out.println("I am " + id + "'th worker thread");
 }
}
public class First
{
 public static void main(String args[]) {
 Worker runnerOne = new Worker(1); // create a thread
 Worker runnerTwo = new Worker(2);
 runnerOne.start(); // start the thread
 runnerTwo.start();
 System.out.println("I am the main thread");
 }
}
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//------------------------------------------------------------------------------------------------------
public class Second extends Thread
{
int id;
Second (int id) {
this.id = id;
}
public void run() {
System.out.println("I am " + id + "'th worker thread.");
 }
 public static void main(String args[]) {
 Second runnerOne = new Second(1);
 Second runnerTwo = new Second(2);
 runnerOne.start();
 runnerTwo.start();
 System.out.println("I am the main thread.");
 }
}
• Disadvantage
o Cannot extend other class
2.2 implements Runnable
• Can extend other class
• Sort of multiple inheritance
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• E.g., public class ThreadApplet extends Applet implements Runnable
class Worker implements Runnable
{
int id;
Worker (int id) {
this.id = id;
}
public void run() {
System.out.println("I am " + id + "'th worker thread.");
 }
}
public class Third
{
 public static void main(String args[]) {
 Runnable worker = new Worker(1);
 Thread runnerOne = new Thread(worker);
 worker = new Worker(2);
 Thread runnerTwo = new Thread(worker);

 runnerOne.start();
 runnerTwo.start();
 System.out.println("I am the main thread.");
 }
}
//------------------------------------------------------------------------------------
public class Fourth implements Runnable
{
int id;
Fourth (int id) {
this.id = id;
}
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public void run() {
System.out.println("I am " + id + "'th worker thread.");
 }
 public static void main(String args[]) {
 Runnable worker = new Fourth(1);
 Thread runnerOne = new Thread(worker);
 Thread runnerTwo = new Thread(new Fourth(2));

 runnerOne.start();
 runnerTwo.start();
 System.out.println("I am the main thread.");
 }
}
3. Joining threads
public class Fifth implements Runnable
{
int id;
Fifth (int id) {
this.id = id;
}
public void run() {
try { Thread.sleep(1000); } // sleep 1000 ms
catch (InterruptedException ie) {}
System.out.println("I am " + id + "'th worker thread.");
 }
 public static void main(String args[]) {
 Runnable worker = new Fifth(1);
 Thread runnerOne = new Thread(worker);
 Thread runnerTwo = new Thread(new Fifth(2));

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 runnerOne.start();
 runnerTwo.start();

 try { runnerOne.join(); } // wait until runnerOne
terminates
 catch(InterruptedException ie) {}
 System.out.println("The first worker done.");

 System.out.println("I am the main thread.");
 }
}
4. Thread cancellation
public class Sixth implements Runnable
{
int id;
Sixth (int id) {
this.id = id;
}
public void run() {
while (true) {
try { Thread.sleep(1000); } // sleep 1000 ms
catch (InterruptedException ie) { // if interrupted
System.out.println("I (" + id + "'th worker) am
interrupted.");
break;
}
System.out.println("I am " + id + "'th worker
thread.");
if (Thread.currentThread().isInterrupted()) { // if
interrupted
System.out.println("I (" + id + "'th worker) am
interrupted.");
break;
}
}
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 }

public static void main(String args[]) {
 Runnable worker = new Sixth(1);
 Thread runnerOne = new Thread(worker);
 Thread runnerTwo = new Thread(new Sixth(2));

 runnerOne.start();
 runnerTwo.start();

 runnerOne.stop(); // stop runnerOne; deprecated

 try { runnerOne.join(); }
 catch(InterruptedException ie) {}
 System.out.println("The first worker done.");

 runnerTwo.interrupt(); // interrupt runnerTwo

 System.out.println("I am the main thread.");
 }
}
5. Shared variable
public class Seventh implements Runnable
{
static int common; // shared among objects, i.e., threads
int id;
Seventh (int id) {
this.id = id;
common = id;
}
public void run() {
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System.out.println("I am " + id + "'th worker thread - " +
common);
 }
 public static void main(String args[]) {
 Thread runnerOne = new Thread(new Seventh(1));
 Thread runnerTwo = new Thread(new Seventh(2));

 runnerOne.start();
 runnerTwo.start();
 System.out.println("I mm the main thread.");
 }
}
Assignment Marking Criteria Weighting
No syntax error: All requirements are fully implemented without syntax
errors. Submitted screen shots will be reviewed with source code. /5
Correct implementation: All requirements are correctly implemented
and produce correct results Submitted screen shots will be reviewed
with source code.
/5
Total /10