notify()

[meena latha]

Hi all....The program below compiles and runs but it hangs
How can i use the notify() to make the program end.
It will be great if some one helps me to solve this.

public class done
{  
  public static void main (String [] args)
 {
        final Food f = new Food();    
    Thread t = new Thread(new Runnable() {
            public void run()
 {
     f.note();

               }
        });  
           t.start();
   }
}
 
 class Food 
{
    int x = 10;   
boolean flag=true; 
public synchronized  void note()
{
if(flag)
try{
System.out.println("Wait");
wait();
}catch(InterruptedException e)
{}
flag=false;
notify();
}
}

Thanks in advance.

[Aruna Agrawal]

See solution . I have added certain things to make the code work.

 
public class done {
public static void main(String[] args) {
final Food f = new Food();
Thread t = new Thread(new Runnable() {
public void run() {
f.note();
 
}
});
t.start();
try {
Thread.sleep(1000*1);
}catch(InterruptedException e) {
e.printStackTrace();
}

System.out.println("after start");
synchronized (f){// this acquires a lock on the required object
System.out.println("after acquire lock");
f.notify();
} // this notify blocked thread to wake up.
System.out.println("after synchronized over");
}
}
 
class Food {
int x = 10;
 
boolean flag = true;
 
public synchronized void note() {
if (flag)
try {
System.out.println("before Wait");
wait();
System.out.println("after Wait");
} catch (InterruptedException e) {
}
flag = false;
notify();
}
}

The thread calls wait() and get into the waiting queue of the object f. but no one wakes it up. so we call notify() from main to wake this thread.

Output
before Wait
after start
after acquire lock
after Wait
after synchronized over

[e-mail]
[ February 20, 2005: Message edited by: Aruna Agrawal ]

[Veer Batra]

How It can be checked that thread while in Thread.sleep(10000*1) has been interuppted and goes to catch block? Thanks in advance.

[Animesh Shrivastava]

Veer,

When any other thread calls the method interrupt() the thread which is sleeping gets interrupted and then the catch block is called

  
public class Done{    
public static void main (String [] args) {        
final Food f = new Food();        
Thread t1 = new Thread(new Runnable() {            
public void run() 
{     
Thread.currentThread().interrupt();               
}        
});         


t1.run();
try {
Thread.sleep(10000);

} catch(InterruptedException e) {
System.out.println("II was in sleep and now i am interrupted....");
}

}  
}

The output of above code is "I was in sleep and now i am interrupted...."

Hope it makes u clear, for more info look at the api

[meena latha]

Hi Animesh
In your program you when used t1.run(),it doesnt starts a new thread.
So when i replaced it with t1.start()the program hangs.

Kindly slove it..

[Animesh Shrivastava]

Hi Ramya,
I am extremely sorry about the above program. Thats a totally wrong program. The correct one is here:

The explanation about the interrupt is explained as in API

If this thread is blocked in an invocation of the wait(), wait(long), or wait(long, int) methods of the Object class, or of the join(), join(long), join(long, int), sleep(long), or sleep(long, int), methods of this class, then its interrupt status will be cleared and it will receive an InterruptedException.

  
public class Done{    
public static void main (String [] args) {  

Thread t1 = new Thread(new Runnable() {            
public synchronized void run() 
{     
try {
      Thread.sleep(1000);      
    } catch(InterruptedException e) {
    System.out.println("I was in sleep and now i am interrupted....");
    }               
}        
});         
t1.start();
System.out.println("hhiii I am going to interrupt Thread t1");
t1.interrupt();
}  
}

Accoridng to API, it says is that if the thread is in sleep state, and if interrupt is called on this thread, its interrupt status gets cleared and the thread is interruped
Hope now its clear