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Multithreading
QUIZQUIZ
QUIZQUIZHow many threads?
public static void main(String[] args) {
y
1. NoneRunnable r1 = new Producer();Runnable r2 = new Producer();Thread t1 = new Thread(r1);
2. One3. Two Thread t1 = new Thread(r1);
Thread t2 = new Thread(r2);
t1.start();
3. Two4. Three5 I don’t know
t2.start();
}
5. I don t know
}
QUIZQUIZHow many threads?
public static void main(String[] args) {
y
1. NoneRunnable r1 = new Producer();Runnable r2 = new Producer();Thread t1 = new Thread(r1);
2. One3. Two Thread t1 = new Thread(r1);
Thread t2 = new Thread(r2);
t1.start();
3. Two4. Three5 I don’t know
t2.start();
}
5. I don t know
}
QUIZQUIZ
Which thread(s)become blocked?
Thread T1 based on run methodpublic void run {
try { Thread.sleep(100000); } 1. Noney { p( ); }catch (InterruptedException e) {}
}
1. None2. T13. T2
Thread T2 based on run method
3. T24. Both5 I don’t know
public void run {factor(785678564567385635789)
}
5. I don t know
}factor method from ”noter” ch. 1
QUIZQUIZ
Which thread(s)become blocked?
Thread T1 based on run methodpublic void run {
try { Thread.sleep(100000); } 1. Noney { p( ); }catch (InterruptedException e) {}
}
1. None2. T13. T2
Thread T2 based on run method
3. T24. Both5 I don’t know
public void run {factor(785678564567385635789)
}
5. I don t know
}factor method from ”noter” ch. 1
public class Test1 implements Runnable {public void run() {
QUIZ
p () {try {
for (int i=1; i<=10; i++) {S t t i tl (i)QUIZ System.out.println(i);Thread.sleep(1000);
}} catch (InterruptedException e) {
} } }
Th t h t t t i t ?The catch statement is empty?1. Compiler error2. Legal code, but better style to omit try-catch3. Legal code, try-catch is necessary, but empty catch is
bad style4. Legal code, try-catch is necessary, empty catch is good
t lstyle5. I don’t know
public class Test1 implements Runnable {public void run() {
QUIZ
p () {try {
for (int i=1; i<=10; i++) {S t t i tl (i)QUIZ System.out.println(i);Thread.sleep(1000);
}} catch (InterruptedException e) {
} } }
Th t h t t t i t ?Good style to swallow Exception
The catch statement is empty?1. Compiler error
only in this context.InterruptedException indicates that
the thread should terminate
2. Legal code, but better style to omit try-catch3. Legal code, try-catch is necessary, but empty catch is
bad style4. Legal code, try-catch is necessary, empty catch is good
t lstyle5. I don’t know
QUIZ Could race condition occur whenrunning these thread in parallel?QUIZ
Producer Thread:BoundedQueue<String> queue
running these thread in parallel?1. Yes2. No3. I don’t knowBoundedQueue<String> queue =
new BoundedQueue<String>(10);for (int i = 1; i <= 100; i++) {
queue.add(i + ": " + greeting);Thread.sleep((int)(Math.random() * DELAY));
}}
Consumer Thread:d d iBoundedQueue<String> queue = new BoundedQueue<String>(10);
for (int i = 1; i <= 100; i++) { Object greeting = queue.remove();System.out.println(greeting); Thread.sleep((int)(Math.random() * DELAY));
}
QUIZ Could race condition occur whenrunning these thread in parallel?QUIZ
Producer Thread:BoundedQueue<String> queue
running these thread in parallel?1. Yes2. No3. I don’t knowBoundedQueue<String> queue =
new BoundedQueue<String>(10);for (int i = 1; i <= 100; i++) {
queue.add(i + ": " + greeting);Thread.sleep((int)(Math.random() * DELAY));
} No race condition since the}
Consumer Thread:d d i
No race condition, since the threads do not use the same
queue object. (This may be a logical error)BoundedQueue<String> queue =
new BoundedQueue<String>(10);for (int i = 1; i <= 100; i++) {
logical error)
Object greeting = queue.remove();System.out.println(greeting); Thread.sleep((int)(Math.random() * DELAY));
}
QUIZ Does it work?QUIZ Does it work?
1: No, race condition may still h k i i id occur
2: Yes race condition cannot
isfull() check is now insidelock protected add()
public void add(E newValue) throws InterruptedException {
2: Yes, race condition cannot occur, and this code works fine
aLock.lock();try {
while( isFull() ) {3: ??? – race condition cannot
occur – but a new problem( () ) {Thread.sleep(1000);
}
occur but a new problem arises…
...} finally {aLock.unlock();}
}
4: I don’t know
QUIZ Does it work?QUIZ Does it work?
1: No, race condition may still h k i i id occur
2: Yes race condition cannot
isfull() check is now insidelock protected add()
public void add(E newValue) throws InterruptedException {
2: Yes, race condition cannot occur, and this code works fine
aLock.lock();try {
while( isFull() ) {3: ??? – race condition cannot
occur – but a new problem( () ) {Thread.sleep(1000);
}
occur but a new problem arises…
...} finally {aLock.unlock();}
}
4: I don’t know
”Deadlock” Since the q e e remains locked no cons mer thread”Deadlock”: Since the queue remains locked, no consumer threadcan execute remove() and make isFull() false
QUIZQUIZWhat is not reason for blocking a thread?g
1. Sleeping 2. Waiting for I/O2. Waiting for I/O3. Time slice is up 4. Waiting to acquire lock4. Waiting to acquire lock5. Waiting for a condition6 I don’t know6. I don t know
QUIZQUIZWhat is not reason for blocking a thread?g
1. Sleeping 2. Waiting for I/O2. Waiting for I/O3. Time slice is up 4. Waiting to acquire lock4. Waiting to acquire lock5. Waiting for a condition6 I don’t know6. I don t know
QUIZQUIZWhen is InterruptedException thrown?p p
1. when Thread.sleep(..) returns2. when <condition>.await() returns2. when condition .await() returns 3. when other thread calls this threads interrupt
method while this thread is blocked4. I don’t know
QUIZQUIZWhen is InterruptedException thrown?p p
1. when Thread.sleep(..) returns2. when <condition>.await() returns2. when condition .await() returns 3. when other thread calls this threads interrupt
method while this thread is blocked4. I don’t know
