• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Ron McLeod
  • Rob Spoor
  • Tim Cooke
  • Junilu Lacar
Sheriffs:
  • Henry Wong
  • Liutauras Vilda
  • Jeanne Boyarsky
Saloon Keepers:
  • Jesse Silverman
  • Tim Holloway
  • Stephan van Hulst
  • Tim Moores
  • Carey Brown
Bartenders:
  • Al Hobbs
  • Mikalai Zaikin
  • Piet Souris

notifyAll() example

 
Ranch Hand
Posts: 96
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Dear all,

In the book of K&B, there is an example about how to use notifyAll() for thread communication. However, in the class Calculator below, if I remove the notifyAll(), the program stills works well. Can anybody tell me why?



And here is the result, it's the same with or without notifyAll().


 
author
Posts: 9031
21
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
This topic is no longer on the SCJP 6 exam. It might still be on the SCJP 5 exam, but really, it's hard to imagine a good reason to take the SCJP 5 exam at this point, so let's move it and the discussion can be continued in Java in General.
 
Ranch Hand
Posts: 35
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Specifically, what part of this is not on the exam? Threads, synchronized, wait() and notifyAll()? I understood serialization was not longer on the exam and I am familiar with the updated objectives. Is there anything new on the exam that is not covered in K&B SCJP 6? Sorry if this is out of scope of the topic. I have been studying threads a lot for the exam...regardless I know it will be helpful in the real world but my focus is to pass the exam.
 
Ranch Hand
Posts: 433
Eclipse IDE Firefox Browser Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
This is actually a very simple example.

3 threads are running all on same instance, which means - synchronized(this) means same for all threads. Lets say we have T-1, T-2,T-3 as threads and C-1 is calculator instance. Let assume that -
> T-2 got the lock over C-1, this leads to T-1 and T-3 both on waiting stage.
> T-2 finishes the calculation and released the lock over C-1. Now you can do either of two things-
1) Notify all the other threads waiting for C-1, by calling C-1.notifyAll( ) or this.notifyAll( ). order of T-1 and T-3 will be random. could be either T-1 then T-3 or vice versa.
2) Leave it as it is, in this case JVM will schedule the running of threads by its own. order of T-1 and T-3 will be random. could be either T-1 then T-3 or vice versa.


Thanks,
 
You showed up just in time for the waffles! And this tiny ad:
Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop
https://coderanch.com/wiki/718759/books/Building-World-Backyard-Paul-Wheaton
reply
    Bookmark Topic Watch Topic
  • New Topic