[Object-Oriented Design Basics] monitor

Author: gnuhpc
Source: http://www.cnblogs.com/gnuhpc/

1) Application Scenario: an object may need to access Shared resources to complete the services it provides. In the case of multiple threads, the combination of multiple such objects will produce unexpected consequences, for example, competition. The monitor sets a lock on such an object to ensure that only one thread can execute any method on this object within a given time.

2) Example: Create a logging class

Public class filelogger {
PublicSynchronizedVoid log (string MSG ){
Dataoutputstream dos = NULL;
Try {
DOS = new dataoutputstream (
New fileoutputstream ("log.txt", true ));
Dos. writebytes (MSG );
Dos. Close ();
} Catch (filenotfoundexception ex ){
//
}
Catch (ioexception ex ){
//
}
}
}

When a thread executes a synchronization method to an object, it gets a lock for this object. When this method is executed, the thread holds this lock to know that the method is running ended, during this period, other threads cannot obtain the lock and therefore cannot execute this method. Of course, the synchronization method is at the cost of running speed overhead.

 

Author: gnuhpc
Source: http://www.cnblogs.com/gnuhpc/