File size: 3,010 Bytes
c574d3a |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 |
class Chat {
boolean flag = false;
public synchronized void sendText(String msg) { // Person-1
if (flag) {
try {
wait();
// ? Why does the wait() call have a warning?
} catch (InterruptedException e) {
e.printStackTrace();
// ? Why does this catch block have a warning?
}
}
System.out.println("Person-1: " + msg);
flag = true;
notify();
// ? Why does using notify() over here lead to a warning?
}
public synchronized void sendReply(String msg) { // Person-2
while (!flag) {
try {
// * ANSWER
/**
* When waiting upon a Condition, a "spurious wakeup" is permitted to occur, in
* general, as a concession to the underlying platform semantics.
*/
wait();
} catch (InterruptedException e) {
// * ANSWER
/**
* InterruptedExceptions should never be ignored in the code, and simply logging
* the exception counts in this case as "ignoring". The throwing of the
* InterruptedException clears the interrupted state of the Thread, so if the
* exception is not handled properly the fact that the thread was interrupted
* will be lost.
*/
e.printStackTrace();
Thread.currentThread().interrupt(); // restore interrupted state
}
}
System.out.println("Person-2: " + msg);
flag = false;
notifyAll();
// * ANSWER
// notify and notifyAll both wake up sleeping threads, but notify only
// rouses one, while notifyAll rouses all of them. Since notify might not wake
// up the right thread, notifyAll should be used instead.
}
}
class Person1 implements Runnable {
Chat personalChat;
String[] messages = { "Hi😀", "Just checking up on you. How are you?", "I am also doing fine.😁" };
public Person1(Chat personalChat) {
this.personalChat = personalChat;
new Thread(this, "Question").start();
}
public void run() {
for (int i = 0; i < messages.length; i++) {
personalChat.sendText(messages[i]);
}
}
}
class Person2 implements Runnable {
Chat personalChat;
String[] messages = { "Hi!🙌", "I am good.👌 What about you?", "Cool!👍" };
public Person2(Chat personalChat) {
this.personalChat = personalChat;
new Thread(this, "Answer").start();
}
public void run() {
for (int i = 0; i < messages.length; i++) {
personalChat.sendReply(messages[i]);
}
}
}
public class ChatThreadSafetyDemo {
public static void main(String[] args) {
Chat justAChat = new Chat();
new Person1(justAChat);
new Person2(justAChat);
}
}
|