Multithreading

class MyThread implements Runnable {

public void run() {

System.out.println(Thread.currentThread().getName());

}

}

public class ThreadTest {

public static void main(String arg[]) {

Thread thread = new Thread(new MyThread());

thread.run();

thread.run();

thread.start();

}

}

• main

  main

  Thread-0

• Thread-0

  main

  Thread-1

• main

  Thread-0

  Thread-1

• Thread-0

  Thread-1

  Thread-2

class MyThread extends Thread {

public MyThread(String name) {

this.setName(name);

}

public void run() {

try {

sleep(100);

} catch (InterruptedException e) {

e.printStackTrace();

}

play();

}

private void play() {

System.out.print(getName());

System.out.print(getName());

}

}

public class ThreadTest {

public static void main(String args[]) throws InterruptedException {

Thread tableThread = new MyThread("Table");

Thread tennisThread = new MyThread("Tennis");

tableThread.start();

tennisThread.start();

}

}

• a) This program will throw an IllegalStateException.

• b) This program will always print the following: Tennis Tennis Table Table.

• c) This program will always print the following: Table Table Tennis Tennis.

• d) The output of this program cannot be predicted; it depends on thread scheduling.

class Worker extends Thread {

public void run() {

System.out.println(Thread.currentThread().getName());

}

}

public class Master {

public static void main(String[] args) throws InterruptedException {

Thread.currentThread().setName("Master ");

Thread worker = new Worker();

worker.setName("Worker ");

worker.start();

Thread.currentThread().join();

System.out.println(Thread.currentThread().getName());

}

}

• a) When executed, the program prints the following: “Worker Master ”.

• b) When executed, the program prints “Worker ”, and after that the program hangs (i.e., does not terminate).

• c) When executed, the program prints “Worker ” and then terminates.

• d) When executed, the program throws IllegalMonitorStateException.

• e) The program does not compile and fails with multiple compiler errors.

What code is missing?

public class MyRunnable implements Runnable

{

public void run()

{

// some code here

}

}

• new Thread(MyRunnable).run();

• new Runnable(MyRunnable).start();

• new Thread(new MyRunnable()).start();

• new MyRunnable().start();

Which of the following line of code is suitable to start a thread?

class Demo implements Runnable

{

public void run() {

System.out.println(“Thread is in Running state”);

}

public static void main(String args[])

{

/* Missing code? */

}

}

• Demo obj = new Demo();

  Thread tobj = new Thread(obj);

  tobj.start();

• Thread t = new Thread(X);

  t.start();

• Thread t = new Thread(Demo);

• Thread t = new Thread();

  Demo.run();

class ThreadDemo extends Thread

{

public static void main(String [] args)

{

ThreadDemo t = new ThreadDemo();

t.start();

System.out.print("one. ");

t.start();

System.out.print("two. ");

}

public void run()

{

System.out.print("Thread ");

}

}

• An exception occurs at runtime.

• Compilation fails.

• . It prints "Thread one. Thread two.".

• The output cannot be determined.

1. public class Test extends Thread{

2. public static void main(String argv[]){

3. Test t = new Test();

4. t.run();

5. t.start();

6. }

7. public void run(){

8. System.out.println("run-test");

9. }

10. }

• A. run-test run-test

• B. run-test

• C. Compilation fails due to an error on line 4

• D. Compilation fails due to an error on line 7

class A implements Runnable{

public void run(){

try{

for(int i=0;i<4;i++){

Thread.sleep(100);

System.out.println(Thread.currentThread().getName());

}

}catch(InterruptedException e){

}

}

}

public class Test{

public static void main(String argv[]) throws Exception{

A a = new A();

Thread t = new Thread(a, "A");

Thread t1 = new Thread(a, "B");

t.start();

t.join();

t1.start();

}

}

• Compilation succeed but Runtime Exception

• A B A B A B A B

• Output order is not guaranteed

• A A A A B B B B