Solved

Java's keyword synchronized

Posted on 2004-09-09
7
345 Views
Last Modified: 2012-06-21
Hey experts,

I read the Java documentation about threads and the interface Runnable, but I kind of couldn't understand the word synchronized (when used in a function header): Does that mean that an entering thread locks mutex before entering this function so it can have sole access to it or does it mean that instructions inside the function are "synchronized" between threads (also sometimes it seemed to mean that threads can be created inside synchronized functions or something like that)

Any explanations would be really helpful
0
Comment
Question by:mte01
  • 4
  • 3
7 Comments
 
LVL 24

Accepted Solution

by:
sciuriware earned 200 total points
ID: 12018540
synchonised is a tag to methods and objects.
It means that provisions are (to be) made so that not 2 or more threads will try to modify
the data and/or to call the method(s) concurrently.
A thread by itself has only one "life" so you can't synchonise it.
A thread calling a synchronised method will "make sure" no other thread "is there"
and will wait until the other one is finished.

There's a lot more, but I recommend you look at the tutorial(s) on the SUN site.

;JOOP!
0
 
LVL 3

Author Comment

by:mte01
ID: 12018612
>> A thread by itself has only one "life" so you can't synchonise it.

What does that mean??
0
 
LVL 24

Expert Comment

by:sciuriware
ID: 12018738
A thread is a single phenomenon: it runs or not.
You can't tell it to wait because it is doing something itself.
From 2 threads on you can.
;JOOP!
0
PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

 
LVL 3

Author Comment

by:mte01
ID: 12018848
Ahaa....what you mean is that with a single thread you don't have to do synchronization (yeh sure that's obvious)
0
 
LVL 3

Author Comment

by:mte01
ID: 12019137
I'll keep the question now open for like an hour for any new useful comments...
0
 
LVL 3

Author Comment

by:mte01
ID: 12020067
I guess that's it......what sciuriware said was more than enough....
0
 
LVL 24

Expert Comment

by:sciuriware
ID: 12023895
One more: be aware that even a tiny program (hello world) has several threads running.
But these are started from the JVM and may be considered safe and balanced.
For you the main thread may be the only thread to account for.
Things get more complex by adding a GUI, which introduces several new threads.
Almost every week you will find some question in this forum that rises
from putting a GUI thread to work from itself.
I wrote some applications with 100's of concurrent threads; only then
things get difficult; unless you know exactly where and how those interfere.
NOT WHEN! you just can not predict WHEN events will interfere.
Therefore we try to control events by 'synchronised' methods and objects.
;JOOP!
0

Featured Post

Master Your Team's Linux and Cloud Stack!

The average business loses $13.5M per year to ineffective training (per 1,000 employees). Keep ahead of the competition and combine in-person quality with online cost and flexibility by training with Linux Academy.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

For customizing the look of your lightweight component and making it look opaque like it was made of plastic.  This tip assumes your component to be of rectangular shape and completely opaque.   (CODE)
An old method to applying the Singleton pattern in your Java code is to check if a static instance, defined in the same class that needs to be instantiated once and only once, is null and then create a new instance; otherwise, the pre-existing insta…
The viewer will learn how to implement Singleton Design Pattern in Java.
Viewers will learn how to properly install Eclipse with the necessary JDK, and will take a look at an introductory Java program. Download Eclipse installation zip file: Extract files from zip file: Download and install JDK 8: Open Eclipse and …

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question