Java.util.concurrent versions: Doug's Lea X J2SDK 1.5.0b31

B31 version of java.util.concurrent has a class named ScheduledExecutor.
The new Doug Lea's code (in his web site) has no such class, but a new one named ScheduledThreadPoolExecutor. He says that we must use the new code, not the code that ships with J2SDK 1.5.0.
Is the new Doug Lea's code scheduled for inclusion in the golden release of J2SDK 1.5.0?

Yes it's my understanding that the final JSR-166 API will be a part of the 1.5.0 'golden release' - any further development of java.util.concurrent would happen under a new JSR .
So yes, following Doug Lea's instructions on the following page will give you a version of java.util.concurrent which is as close as possible to the one we'll be using when 1.5.0 is released.
http://gee.cs.oswego.edu/dl/concurrency-interest/index.html
Mark

Similar Messages

FU Ant task failure: java.util.concurrent.ExecutionException: could not close client/server socket

We sometimes see this failure intermitently when using the FlexUnit Ant task to run tests in a CI environment. The Ant task throws this exception:
java.util.concurrent.ExecutionException: could not close client/server socket
I have seen this for a while now, and still see it with the latest 4.1 RC versions.
Here is the console output seen along with the above exception:
FlexUnit player target: flash
Validating task attributes ...
Generating default values ...
Using default working dir [C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\Source\Flex]
Using the following settings for the test run:
FLEX_HOME: [C:\dev\vert-d3flxcmn32\302100.41.0.20110323122739_d3flxcmn32]
haltonfailure: [false]
headless: [false]
display: [99]
localTrusted: [true]
player: [flash]
port: [1024]
swf: [C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\build\commons.formatter.tests.unit.sw f]
timeout: [1800000ms]
toDir: [C:\DJTE\commons.formatter_swc\d3flxcmn32\reports\xml]
Setting up server process ...
Entry [C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\build] already available in local trust file at [C:\Users\user\AppData\Roaming\Macromedia\Flash Player\#Security\FlashPlayerTrust\flexUnit.cfg].
Executing 'rundll32' with arguments:
'url.dll,FileProtocolHandler'
'C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\build\commons.formatter.tests.unit.swf '
The ' characters around the executable and arguments are
not part of the command.
Starting server ...
Opening server socket on port [1024].
Waiting for client connection ...
Client connected.
Setting inbound buffer size to [262144] bytes.
Receiving data ...
Sending acknowledgement to player to start sending test data ...
Stopping server ...
End of test data reached, sending acknowledgement to player ...
When the problem occurs, it is not always during the running of any particular test (that I am aware of). Recent runs where this failure was seen had the following number of tests executed (note: the total number that should be run is 45677): 18021, 18, 229.
Here is a "good" run when the problem does not occur:
Setting inbound buffer size to [262144] bytes.
Receiving data ...
Sending acknowledgement to player to start sending test data ...
Stopping server ...
End of test data reached, sending acknowledgement to player ...
Closing client connection ...
Closing server on port [1024] ...
Analyzing reports ...
Suite: com.formatters.help.TestGeographicSiteUrls
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.008 sec
Suite: com.formatters.functionalUnitTest.testCases.TestNumericUDF
Tests run: 13, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.071 sec
Results :
Tests run: 45,677, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 201.186 sec
Has anyone else ran across this problem?
Thanks,
Trevor

I am not sure if this information will help everyone, but here goes...
For us, these problems with FlexUnit tests crashing the Flash Player appear to be related to couple of factors. Recently, we moved up from Flex 3.2 to Flex 4.1 as our development baseline. Many people complained that their development environment (Flash Builder, etc.) was much more unstable. Apparently, 4.1 produces SWFs that require more memory to run than 3.2 does? Anyway, we still had Flash Player 10.1 as our runtime baseline. Apparently, that version of the player was not as capable of running larger FlexUnit test SWFs, and would crash (as I posted months earlier). I upgraded to the latest 10.3 standalone player versions, and the crashes have now ceased. It would be nice to know exactly what was causing the crashes, but memory management (or lack of) is my best guess.
So, if you are seeing these issues, try upgrading to the latest Flash Player version.
Regards,
Trevor

Supplementing java.util.concurrent.TimeUnit with a Duration?

Ever since the concurrency classes were introduced in Java 5 have I been wondering why they designed all the interfaces so clumsily with regards to specifying durations:
every method that expects an amount of time needs 2 parameters, one for the value and one for the unit. IMHO that should have been just one value-object!
So in my projects I'm using a class called "Duration" that encapsulates a long value together with a TimeUnit. http://www.neppert.com/duration/doc/index.html
It has turned out to be extremely handy, because it adheres to the DRY rule: only once, usually when reading timeouts from UIs or properties files into Durations do I need to consider the value's unit.
Now when a user tells me "I don't want to type in stupid milliseconds, I want minutes", it's just one place I have to change ;-)
Would it be good to have such a class in the JDK?

jiju wrote:
check whether import java.util.concurrent.*; is workingAwesome.
As for netbeans, I went and double checked to see if it is reading from the most updated folder of Java and it is.
So as I said, I am totally lost as to why it's not working. Should I just downgrade to a lower version of Java? Although it would seem kinda weird to do something like this.

Java.util.concurrent.ConcurrentHashMap

All,
I prefer to use the java.util.ConcurrentHashMap over a Hashtable but there are some points regarding this structure that are not very clear to me.
From java.util.concurrent: Class ConcurrentHashMap:
"A hash table supporting full concurrency of retrievals and adjustable expected concurrency for updates. This class obeys the same functional specification as Hashtable, and includes versions of methods corresponding to each method of Hashtable.
*+However, even though all operations are thread-safe, retrieval operations do not entail locking, and there is not any support for locking the entire table in a way that prevents all access. This class is fully interoperable with Hashtable in programs that rely on its thread safety but not on its synchronization details. Iterators are designed to be used by only one thread at a time."+ *
Also from: Java API: Package java.util.concurrent, we read:
"The "Concurrent" prefix used with some classes in this package is a shorthand indicating several differences from similar "synchronized" classes. For example java.util.Hashtable and Collections.synchronizedMap(new HashMap()) are synchronized. But ConcurrentHashMap is "concurrent". A concurrent collection is thread-safe, but not governed by a single exclusion lock. In the particular case of ConcurrentHashMap, it safely permits any number of concurrent reads as well as a tunable number of concurrent writes. "Synchronized" classes can be useful when you need to prevent all access to a collection via a single lock, at the expense of poorer scalability. In other cases in which multiple threads are expected to access a common collection, "concurrent" versions are normally preferable. And unsynchronized collections are preferable when either collections are unshared, or are accessible only when holding other locks."
Based on above, is this correct of I say:
When using a structure like Hashtable, all the methods or operations are synchronized,
meaning if one thread is accessing the Hashtable (by get(), put(),... or other methods on this structure), it owns the lock and all other threads will lock out until the thread that owns the lock releases the lock; which means only one thread can access the hash table at a time; which can cause performance issues.
We need to use a synchronized block or method only of two threads modify a "shared resource", if they do not modify a shared resource, we do not need to use the synchronization.
On the other hand, the methods of ConcurrentHashMap are not synchronized; so multiple threads can access the ConcurrentHashMap at the same time. But isn't the ConcurrentHashMap itself the "shared resource" that threads are accessing? Should we use it only if the threads are reading from map and not writing to it? And then if threads also write to the structure, then it looks like its better to not to use the ConcurrentHashMap, rather use the regular HashMap with the synchronized wrapper?
Any help is greatly appreciated.

We need to use a synchronized block or method only of two threads modify a "shared resource", if they do not modify a shared resource, we do not need to use the synchronization. Actually, you need to synchronize access to the shared resource for both readers and writers. If one thread is updating an unsynchronized HashMap, and a concurrent thread tries to read that map, it may be in an inconsistent state. When synchronizing on the map, the reader will be blocked until the writer completes.
What you don't need to do is prevent multiple readers from accessing the map, if there's no writer. However, a synchronized map or HashTable will single-thread reads as well as writes.
On the other hand, the methods of ConcurrentHashMap are not synchronized; so multiple threads can access the ConcurrentHashMap at the same time. But isn't the ConcurrentHashMap itself the "shared resource" that threads are accessing? No, it's actually synchronized at a finer level. Without getting into the details of HashMap implementation, an object's hashcode is used to identify a linked list of hashmap entries. The only time that you have a concurrency issue is when a reader and writer are accessing the same list. So the ConcurrentHashMap locks only the list that's being updated, and allows readers (and writers!) to access the other bucket lists. Plus, it allows two readers to proceed concurrently.

A problem with importing java.util.concurrent

I am rather new to Java with not that much experience. I apologize ahead though if this is the inappropriate forum to post this problem and/or this question has been answered somewhere else (I couldn't find a post on this subject).
Some of my research has lead to using a semaphore if you wish to use the synchronized() method. I looked up that the import for that is under java.util.concurrent.Semaphore; however, thanks to netbeans for pointing this out before I compiled it, this doesn't seem to exist.
I'm using Java version 1.6.0_03 which does seem to be the latest version. Was it simply removed or am I seriously missing something big here? Anyways, I'm at a total loss and hopefully someone can point me in the right direction.
Thank you in advance for your help.

jiju wrote:
check whether import java.util.concurrent.*; is workingAwesome.
As for netbeans, I went and double checked to see if it is reading from the most updated folder of Java and it is.
So as I said, I am totally lost as to why it's not working. Should I just downgrade to a lower version of Java? Although it would seem kinda weird to do something like this.

Java.util.concurrent.*;

i am comming up with this error when i compile my code "package java.util.concurrent does not exist"
i have the code
import java.util.concurrent.*;
and i have just updated my java java SE 6 update 5.
i am using netbeans 3.6.
does anybody know what my problem is???????

Ouch, is there a reason why you're still using Netbeans 3.6 instead of something a little more recent? The newer versions are much improved.
It's been a very long time since I used 3.6, but I seem to recall that you can change the JDK used by 3.6 by changing one of the configuration files. Should be something like $NETBEANS_HOME/etc/netbeans.conf. In that file should be a jdkhome variable.

Java.io.InvalidClassException: java.util.concurrent.SynchronousQueue$WaitQu

version: 1.6.0-beta2-b86
I want to call a remote method using RMI to pass back a serialized Remote object that is composed of two SynchronousQueue objects. The exception that I get when I call the method is below.
Client exception: java.rmi.UnmarshalException: error unmarshalling return; nested exception is:
        java.io.InvalidClassException: java.util.concurrent.SynchronousQueue$WaitQueue; local class incompatible: stream classdesc seria
lVersionUID = 4403964863567356358, local class serialVersionUID = -858510627080488182
java.rmi.UnmarshalException: error unmarshalling return; nested exception is:
        java.io.InvalidClassException: java.util.concurrent.SynchronousQueue$WaitQueue; local class incompatible: stream classdesc seria
lVersionUID = 4403964863567356358, local class serialVersionUID = -858510627080488182
        at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:173)
        at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178)
        at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132)
        at $Proxy0.register(Unknown Source)
        at ExchangeClient.main(ExchangeClient.java:30)
Caused by: java.io.InvalidClassException: java.util.concurrent.SynchronousQueue$WaitQueue; local class incompatible: stream classdesc se
rialVersionUID = 4403964863567356358, local class serialVersionUID = -858510627080488182
        at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:562)
        at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
        at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1732)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1945)
        at java.io.ObjectInputStream.defaultReadObject(ObjectInputStream.java:480)
        at java.util.concurrent.SynchronousQueue.readObject(SynchronousQueue.java:1120)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:589)
        at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1846)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1945)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1869)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
        at sun.rmi.server.UnicastRef.unmarshalValue(UnicastRef.java:306)
        at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:155

hi,
is this j2ee application ur trying to deploy on app server?
if so u could try re-deploying ur application and check ur settings again..datasources etc , see to it that u hv given rite and correct values for jdbc drivers,jdbc url,check java classes used,DS etc for the j2ee app in ur EM website.
or try re-starting that oc4j component that was used , maybe this could help.god bless:)
Edited by: lillyak on Mar 16, 2009 11:58 PM

Using ExecutorService class from java.util.concurrent package

Dear java programmers,
I have a question regarding the ExecutorService class from java.util.concurrent package.
I want to parse hundreds of files and for this purpose I'm implementing a thread pool. The way I use the ExecutorService class is summarized below:
ExecutorService executor = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 1000; i++){
            System.out.println("Parsing file No "+i);
            executor.submit(new Dock(i));
        executor.shutdown();
        try {
            executor.awaitTermination(30, TimeUnit.SECONDS);
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        executor.shutdownNow();However, the code snippet above creates all the 1000 threads (Dock objects) at once and loads them to the executor, and thus I'm worrying about memory leak. I haven't tested it on 1000 files yet but just on 50 small ones, and even if the program prints out "Parsing file No "+i 50 times at once, it executes normally the threads in the background.
I guess the write way would be to keep the number of active/idle threads in the executor constant (lets say 20 if the thread pool's size is 10) and submit a new one whenever a thread has been finished or terminated. But for this to happen the program should be notified someway whenever a thread is done. Can anybody help me do that?
thanks in advance,
Tom

Ok I found a feasible solution myself although I'm not sure if this is the optimum.
Here's what I did:
        ExecutorService executor = Executors.newFixedThreadPool(10);
        Future<String> future0, future1, future2, future3, future4, future5, future6, future7, future8, future9;
        Future[] futureArray = {future0 = null, future1 = null, future2 = null, future3 = null, future4 = null, future5 = null,
        future6 = null, future7 = null, future8 = null, future9 = null};
        for (int i = 0; i < 10; i++){
            futureArray[i] = executor.submit(new Dock(i));
        }I created the ExecutorService object which encapsulates the thread pool and then created 10 Future objects (java.util.concurrent.Future) and added them into an Array.
For java.util.concurrent.Future and Callable Interface usage refer to:
[http://www.swingwiki.org/best:use_worker_thread_for_long_operations]
[http://www.particle.kth.se/~lindsey/JavaCourse/Book/Part1/Java/Chapter10/concurrencyTools.html]
I used a Future[] Array to make the code neater. So after that I submitted -and in this way filled up- the first 10 threads to the thread pool.
        int i = 9;
        while (i < 1000){
            for (int j = 0; j < 10; j++){
                if (futureArray[j].isDone() && i < 999){
                    try{
                        i++;
                        futureArray[j] = executor.submit(new Dock(i));
                    } catch (ExecutionException ex) {
                        ex.printStackTrace();
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();
            try {
                Thread.sleep(100); // wait a while
            } catch(InterruptedException iex) { /* ignore */ }
        executor.shutdown();
        try {
            executor.awaitTermination(60, TimeUnit.SECONDS);
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        executor.shutdownNow();
    }Each of the future[0-9] objects represents a thread in the thread pool. So essentially I'm check which of these 10 threads has been finished (using the java.util.concurrent.Future.isDone() method) and if yes I replenish that empty future[0-9] object with a new one.

Java.util.concurrent.ExecutorService inside J2EE Container

I want to use the JDK 1.5 concurrency class ExecutorService for concurrent execution of data-access logic inside my oc4j web-application.
I'm using the Factory Executors.newFixedThreadPool(6) for creating a thread-pool.
I know that it's not a good practice to create new threads inside a j2ee container.
Is there anything I have to think of or beware of??
Perhaps anybody here has experience using the java.util.concurrent.Executor inside OC4J or an other j2ee container.
Thanks, Harald

Yes, I have used java.util.concurrent.Executor in weblogic 10 server.
You can really improve the performance of the EJB application if you use the thread pool carefully with limited size say 100 threads, by creating a single instance of thread pool for the whole J2EE application.
You have to control the life cycle of thread pool using the container's life cycle methods, create the thread pool only once and destroy every time you recycle your app.
Good luck with the implementation :)

Java.util.concurrent.ExecutorService inside OC4J

I want to use the JDK 1.5 concurrency class ExecutorService for concurrent execution of data-access logic inside my oc4j web-application. I'm using the Factory Executors.newFixedThreadPool(6) for creating a thread-pool.
I know that it's not a good practice to create new threads inside a j2ee container.
Is there anything I have to think of or beware of??
Perhaps anybody here has experience using the java.util.concurrent.Executor inside OC4J.
Thanks, Harald

Yes, I have used java.util.concurrent.Executor in weblogic 10 server.
You can really improve the performance of the EJB application if you use the thread pool carefully with limited size say 100 threads, by creating a single instance of thread pool for the whole J2EE application.
You have to control the life cycle of thread pool using the container's life cycle methods, create the thread pool only once and destroy every time you recycle your app.
Good luck with the implementation :)

Cannot import java.util.concurrent.locks ... WHY?

Why is Xcode unable to find the java.util.concurrent.locks package. The class browser knows it exists. For example the entry for the ReentrantLock class looks like this in the browser class window:
ReentrantLock (java.util.concurrent.locks)
Xcode knows about other java.util packages such as java.util.ResourceBundle which I have been accessed successfully in other parts of my projecgt.
Here is a source file and the resulting compiler error:
The source file:
// Foo.java
import java.util.ResourceBundle;
import java.util.concurrent.locks;
public class Foo { }
The compiler error:
compile:
Compiling 2 source files to /Users/Terry/Desktop/JAVA/PROJECTS/Logic/bin
/Users/Terry/Desktop/JAVA/PROJECTS/Logic/src/Foo.java:3: cannot find symbol
symbol : class locks
location: package java.util.concurrent
import java.util.concurrent.locks;
^
1 error
BUILD FAILED
Help or hints would be greatly appreciated!

Well the reason to your problem is very simple... java.util.concurrent.locks is a package... Not a class.
if you want to import a specific class, the class should be written at the end like you did for import java.util.ResourceBundle; but if you want to import a whole package you need to add the little star at the end :
import java.util.concurrent.locks.*;
Or else, you only import the class you need :
import java.util.concurrent.locks.ReentrantLock;

Java.util.concurrent.LinkedBlockingDeque: cannot find symbol

Hello,
I'm trying to use an existing java code into a JavaFX application. To do this, I copied all my sources into the fx project in Netbeans and I linked the needed libraries, but when I tried to compile all this, I got the following message:
"cannot find symbol
symbol : class LinkedBlockingDeque
location: package java.util.concurrent
import java.util.concurrent.LinkedBlockingDeque;"
the problem is at that line: import java.util.concurrent.LinkedBlockingDeque;
This is a native java class. Is it not supported in JavaFx? Is not java fully compatible with Fx? What's happening?
Thank you in advance

Please, create an issue on it with the detailed comments: [http://www.netbeans.org/issues/enter_bug.cgi?component=javafx|http://www.netbeans.org/issues/enter_bug.cgi?component=javafx]

Java.util.concurrent.XYZ and cloneable

Hello!
How come that collection classes in java.util.concurrent do not implement Cloneable?
On 01.06.2004 there was a bug report on CopyOnWriteArraySet regarding this:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5055732
However, on 02.06.2004 the cloneable support was removed from the JSR166 repository?!
http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/main/java/util/concurrent/ConcurrentHashMap.java?rev=1.48&content-type=text/vnd.viewcvs-markup
Best regards,
Thomas

Hello!
How come that collection classes in java.util.concurrent do not implement Cloneable?
On 01.06.2004 there was a bug report on CopyOnWriteArraySet regarding this:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5055732
However, on 02.06.2004 the cloneable support was removed from the JSR166 repository?!
http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/main/java/util/concurrent/ConcurrentHashMap.java?rev=1.48&content-type=text/vnd.viewcvs-markup
Best regards,
Thomas

Java.util.concurrent.ExecutorService question!!!

HI,
I'm working with java.util.concurrent.ExecutorService. I need to know: Is there a possibility to know that all executions are done, that there is nothing to execute?????
All ideas are welcome!:)
Thanks a lot!:)
Best,
Aram.

If I understood If I will use maxpoolsize of 1 that will be like Executors.newSingleThreadPool()?????It will be like SingleThreadPool, except that you can supply your own queue, with its own queueing characteristics. Also, there is no need to use five question-marks; four will suffice.
Your tasks will be executed in the order they are in in the queue; read the documentation for the queue you choose for details. "Priority" is not a built-in concept in Java. You must implement the Comparable interface so that the priority-queue can tell which task should be executed next.
And what "second queue"? A given executor will execute tasks off one queue.
M.

Java.util.concurrent.ConcurrentLinkedQueue efficient?

If I need to put, say, 2K-3K nodes in a second in a multi threaded environment, would ConcurrentLinkedQueue of java.util.concurrent package of java version1.5 be efficeint ? Or should I use something lese??
Thanks in advance..

my whole code is in java, I am listening to two multicast sockets, and receiveing messages. I am missing a few data when it peaks to 2K-3K in a second. to resolve this, I thought of putting everything I receive to a shared buffer before i do anything to these messages, and process them from later. so, I thought of using ConcurrentLinkedQueue as temp buffer.

Java.util.concurrent versions: Doug's Lea X J2SDK 1.5.0b31

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