Trying to implement the Observer pattern with a notify() method

OK, I'm not implementing the observer exactly rigidly but I'm doing something thereabouts inline with the pattern. I have an abstract class which provides some common functionality for the observers and is also used for type checking elsewhere. Each observer must inherit from this class. Now; the abstract class has one abstract method notify() as per the generic observer.
I get an error that notify() cannot be overridden as it's final. I understand what all that means but I'm curious where it's implemented that's actually affecting my own code? Is notify() a standard method in all objects in Java?
package zoopackage;
public abstract class ZooObserver
     protected Cage cage;
     public void setCage(Cage myCage)
          this.cage = myCage;
     abstract public void notify();
}And...
package zoopackage.observers;
import zoopackage.*;
public class VisualObserver extends ZooObserver
     public void notify()
}

Is notify() a standard method in all objects in Java?Yes, as are notifyAll() and wait(). You'll also notice in the API that there already is an Observer interface and an Observable object. That's probably sufficient to implement what you want to do.
Brian

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Trying to implement the Builder pattern with inheritance

This is just a bit long, but don't worry, it's very understandable.
I'm applying the Builder pattern found in Effective Java (J. Bloch). The pattern is avaiable right here :
http://books.google.fr/books?id=ka2VUBqHiWkC&lpg=PA15&ots=yXGmIjr3M2&dq=nutritionfacts%20builder%20java&pg=PA14
My issue is due to the fact that I have to implement that pattern on an abstract class and its extensions. I have declared a Builder inside the base class, and the extensions specify their own extension of the base's Builder.
The abstract base class is roughly this :
public abstract class Effect extends Trigger implements Cloneable {
    protected Ability parent_ability;
    protected Targetable target;
    protected EffectBinder binder;
    protected Effect(){
    protected Effect(EffectBuilder parBuilder){
        parent_ability = parBuilder.parent_ability;
        target = parBuilder.target;
        binder = parBuilder.binder;
    public static class EffectBuilder {
        protected Ability parent_ability;
        protected Targetable target;
        protected EffectBinder binder;
        protected EffectBuilder() {}
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        public EffectBuilder target(Targetable parTarget)
        { target = parTarget; return this; }
        public EffectBuilder binder(EffectBinder parBinder)
        { binder = parBinder ; return this; }
    // etc.
}And the following is one of its implementation :
public class GainGoldEffect extends Effect {
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    public GainGoldEffect(GainGoldEffectBuilder parBuilder) {
        super(parBuilder);
        gold_gain = parBuilder.gold_gain;
    public class GainGoldEffectBuilder extends EffectBuilder {
        private int gold_gain;
        public GainGoldEffectBuilder(int parGoldGain, Ability parParentAbility) {
            this.gold_gain = parGoldGain;
            super.parent_ability = parParentAbility;
        public GainGoldEffectBuilder goldGain(int parGoldGain)
        { gold_gain = parGoldGain; return this; }
        public GainGoldEffect build() {
            return new GainGoldEffect(this);
    // etc.
}Effect requires 1 parameter to be correctly instantiated (parent_ability), and 2 others that are optional (target and binder). Implementing the Builder Pattern means that I won't have to rewrite specific construcors that cover all the combination of parameters of the Effect base class, plus their own parameter as an extension. I expect the gain to be quite huge, as there will be at least a hundred of Effects in this API.
But... in the case of these 2 classes, when I'm trying to create the a GoldGainEffect like this :
new GainGoldEffect.GainGoldEffectBuilder(1 , locAbility).goldGain(5);the compiler says "GainGoldEffect is not an enclosing class". Is there something wrong with the way I'm trying to extend the base Builder ?
I need your help to understand this and find a solution.
Thank you for reading.

The GainGoldEffectBuilder class must be static.
Otherwise a Builder would require a GainGoldEffect object to exist, which is backwards.

Observer pattern with TCP

Hello java friends!
I have implemented an auction application over a TCP communication. The client's using a basis Socket and the server is multi threaded with a ServerSocket returning a Socket which is processed in a separate thread. The connection between server and client is closed automatic after each request, so another request from the client would need to be connected over a new connection. It's implemented like this for the sake of performance.
But however, I now want to implement the Observer pattern(which I'm also comfortable with). This would let the client be notified by the server if someone else overbids him in a auction. And I wonder how this could be completed?
I had a thought and it went like this. If the client would also have a ServerSocket then the server would be able to connect to it when ever he would like to notifying the client. What I like by this implementation is that the notification is done without any delay! This is obviously one way to implement it, but I wonder if someone else in here had a better idea,or if someone knew the standard implementation for a situation like this.
Thanks in regards!

superdeportivo wrote:
The sever creates a new thread for every request that the client makes. If performance is important you may want to use a thread pool.
For example the client makes a bid on an auction item. [deleted]This is simplest way to do what you require. I am generally in favour of keeping things simple.
if the Client would like to make another bid then the client would need to go through all the steps again from 1 to 4. Why the fourth step is implemented is because otherwise the client would held a thread live at the server as long as he is connected (using the application) and eventually the server would run out of threads!How many clients do you have at once? You should be able to support 1,000 on a typical PC and 10,000 on a decent server. You can keep the connection/thread for a period of time and drop the connection if the client disconnects or doesn't do anything for a period of time (from a few seconds to a few hours)
Another approach is to use non-blocking IO (see the samples which come with the JDK) In this way a small number of threads can manage a large number of connections.
So lets say if we're using a thread pool with maximum 20 threads, then only 20 clients would be able to connect to the server at the same time (use the application). If the maximum is 2,000 then you can have up to 2,000 clients.
I hope I made my self clear if not please tell me which part wasn't.I think you have made a few assumptions about what performs best or what is possible could have a rethink.
And about the delay, of course the connection delay is what's acceptable for my program.The simplest approach using your current model is for the client to poll the server.
Edited by: Peter__Lawrey on 30-Jan-2009 22:56

Trying to use the JSSE library with Jrocket 7.0

Hi All,
I HAC who is trying to use the JSSE library with Jrocket 7.0.
Sometimes the socket works and sometimes it does not. It throws the below
exception,
The exception stacktrace is given below:
java.net.SocketException: SSL implementation not available
at
javax.net.ssl.DefaultSSLSocketFactory.createSocket(Ljava.lang.String;I)Ljava
.net.Socket;(Unknown Source)
at
com.twister.transunion.TransUnionUtils.sendRequest(Ljava.lang.String;)Ljava.
lang.String;(Unknown Source)
at
com.twister.transunion.TransUnionUtils.parseRequest(Lcom.twister.transunion.
TransUnionRequest;)Z(Unknown Source)
at
com.twister.struts.signup.Signup5Action.button_apply_now(Lorg.apache.struts.
action.ActionMapping;Lorg.apache.struts.action.ActionForm;Ljavax.servlet.htt
p.HttpServletRequest;Ljavax.servlet.http.HttpServletResponse;)Lorg.apache.st
ruts.action.ActionForward;(Unknown Source)
at
COM.jrockit.reflect.NativeMethodInvoker.invoke0(ILjava.lang.Object;[Ljava.la
ng.Object;)Ljava.lang.Object;(Unknown Source)
at
COM.jrockit.reflect.NativeMethodInvoker.invoke(Ljava.lang.Object;[Ljava.lang
.Object;)Ljava.lang.Object;(Unknown Sou
the line of code causing the stack trace is:
Socket socket =
javax.net.ssl.SSLSocketFactory.getDefault().createSocket(HOST, PORT);
He has added the following line to his jre/lib/security/java.security file:
security.provider.3=com.sun.net.ssl.internal.ssl.Provider
and he has added the JSSE jar files to the jre/lib/ext directory.
The problem occurs when SSL is enabled in the config.xml file (e.g. <SSL
Enabled="true" ...>). It does NOT occur when SSL is disabled.
When SSL is disabled, the following code shows all three providers as
defined in the java.security file. If SSL is enabled then he only sees the
default 2 implementation and NOT the one he added above.
java.security.Provider[] a = java.security.Security.getProviders();
for (int i=0; i < a.length; i++)
System.out.println("name: " + a.getName());
System.out.println("ver: " + a[i].getVersion());
System.out.println("info: " + a[i].getInfo());
The problem is that client does not want to use WebLogic specific classes to
create an SSL socket. As well he do NOT wish to dynamically register the
SunJSSE provider. Since this setup works when SSL is disabled in WebLogic he
believes he has configured everything properly.
It appears to me that WebLogic is removing the JSSE as a security provider
if SSL is enabled.
Is it the expected behaviour? and Is it possible to statically register the
JSSE provider in the jre/lib/security/java.security file ?
Any pointers will be appreciated,
Thanks in advance,
Rubesh

Hi Howard, just trawling through the Labview TE issues as I myself have started to work on a similar issue. I have now infact upgraded the Labview Test Executive to work in 7.1 ok (both development and Runtime).
Using XP I had no issues upgrading in the development environment - creating the run-time version was not as easy but manged to do so with help from the Application Builder. I have also tested the SQL function (as i log to Oracle) and a basic audio test using a DSA4551 - again both seem to be upgraded with no issues.
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Implementing the Singleton pattern

Has anyone implemented the singleton pattern in Forte? A singleton is simply ensuring that there is one unique instance of a class. In other OO languages I would create a class method which would use a class variable to hold onto the unique instance. Since forte doesn't have either of these (class methods or variables), I'm not sure how to do it. I thought of using named objects, but it seems like a heavy implementation. Any ideas.

An SO with its shared=TRUE and anchored=TRUE?
Venkat J Kodumudi
Price Waterhouse LLP
Internet: [email protected]
Internet2: [email protected]
-----Original Message-----
From: [email protected] [SMTP:[email protected]]
Sent: Monday, February 02, 1998 1:09 PM
To: Venkat Kodumudi
Subject: Implementing the Singleton pattern
To: [email protected] @ Internet
cc:
From: [email protected] @ Internet
Date: 02/02/98 12:36:02 PM
Subject: Implementing the Singleton pattern
Has anyone implemented the singleton pattern in Forte? A singleton is
simply
ensuring that there is one unique instance of a class. In other OO
languages I
would create a class method which would use a class variable to hold
onto the
unique instance. Since forte doesn't have either of these (class
methods or
variables), I'm not sure how to do it. I thought of using named
objects, but it
seems like a heavy implementation. Any ideas.

Error while trying to invoice the delivery doc with future date

Hi Gurus,
I am trying to create the Invoice document with future date with reference to delivery document,but the system is not allowing to do and its throwing the error message billing date is greater than current date not authorized.How to resolve this issue.
Thanks and Regards,
hari Challa.

Dear Hari
Curious to know why you are trying to maintain a future date in billing when you yourself very well know that it is WRONG. Logically, the invoice date should be either Actual GI Date from Delivery or the system date.
Coming to your question, in VTFL, for your item category if routine 11 is maintained for the field Data VBRK/VBRP, you cannot achieve what you want.
thanks
G. Lakshmipathi

Serializing a class that implements the Singleton pattern

Hello,
I am relatively new to Java and especially to serialization so the answer to this question might be obvious, but I could not make it work event though I have read the documentation and the article "Using XML Encoder" that was linked from the documentation.
I have a class that implements the singleton pattern. It's definition is as follows:
public class JCOption implements Serializable {
private int x = 1;
private static JCOption option = new JCOption();
private JCOption() {}
public static JCOption getOption() { return option; }
public int getX() { return x; }
public void setX(int x) { this.x = x; }
public static void main(String args[]) throws IOException {
    JCOption opt = JCOption.getOption();
    opt.setX(10);
    XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(new FileOutputStream("Test.xml")));
    encoder.setPersistenceDelegate(opt.getClass(), new JCOptionPersistenceDelegate());
    encoder.writeObject(opt);
    encoder.close();
}Since this class does not fully comply to the JavaBeans conventions by not having a public no-argument constructor, I have create a class JCOptionPersistenceDelegate that extends the PersistenceDelegate. The implementation of the instantiate method is as follows:
protected Expression instantiate(Object oldInstance, Encoder out) {
       Expression expression = new Expression(oldInstance, oldInstance.getClass(), "getOption", new Object[]{});
        return expression;
}The problem is that the resulting XML file only contains the following lines:
    <java version="1.5.0_06" class="java.beans.XMLDecoder">
        <object class="JCOption" property="option"/>
    </java> so there is no trace of the property x.
Thank you in advance for your answers.

How about this:
import java.beans.DefaultPersistenceDelegate;
import java.beans.Encoder;
import java.beans.Expression;
import java.beans.Statement;
import java.beans.XMLEncoder;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class JCOption {
    private int x = 1;
    private static JCOption option = new JCOption();
    private JCOption() {}
    public static JCOption getOption() { return option; }
    public int getX() { return x; }
    public void setX(int x) { this.x = x; }
    public static void main(String args[]) throws IOException {
      JCOption opt = JCOption.getOption();
      opt.setX(10);
      ByteArrayOutputStream os = new ByteArrayOutputStream();
      XMLEncoder encoder = new XMLEncoder( os );
      encoder.setPersistenceDelegate( opt.getClass(), new JCOptionPersistenceDelegate() );
      encoder.writeObject(opt);
      encoder.close();
      System.out.println( os.toString() );
class JCOptionPersistenceDelegate extends DefaultPersistenceDelegate {
    protected Expression instantiate(Object oldInstance, Encoder out) {
        return new Expression(
                oldInstance,
                oldInstance.getClass(),
                "getOption",
                new Object[]{} );
    protected void initialize( Class<?> type, Object oldInstance, Object newInstance, Encoder out ) {
        super.initialize( type, oldInstance, newInstance, out );
        JCOption q = (JCOption)oldInstance;
        out.writeStatement( new Statement( oldInstance, "setX", new Object[] { q.getX() } ) );
}   Output:
<?xml version="1.0" encoding="UTF-8"?>
<java version="1.5.0_06" class="java.beans.XMLDecoder">
<object class="JCOption" property="option">
<void property="x">
   <int>10</int>
</void>
</object>
</java>

The Observer Pattern

I need to help on the Observer pattern. It's true/false questions:
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2. You cannot reuse subjects without reusing their observers, and vice versa.
3. You cannot add observers without modifying the subject or other observers.
4. The coupling between subjects and observers is abstract and minimal.
5. Like an ordinary request, the notification that a subject sends must specify its receiver.
6. In some situations an observer depends on more than one subject, for example, a spreadsheet may depend on more than one data source.
Thanks
Brendan

Please check if correct. THe reason why I asked for help is because I have not found any good articles on this pattern and it is not part of my curriculum, but we have to answer it.
1. TRUE
2. FALSE
3. FALSE
4. TRUE
5. FALSE
6. TRUE
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Thanks

I have turned off my iphone 5s but i got a blue screen when i tried to turn it on back, and i tried to press the power button with the home button but it wont work

i have turned off my iphone 5s but i got a blue screen when i tried to turn it on back, and i tried to press the power button with the home button but it wont work

fadijaber wrote:
i have turned off my iphone 5s but i got a blue screen when i tried to turn it on back,
The Basic Troubleshooting Steps are:
Restart... Reset... Restore from Backup... Restore as New...
Restart / Reset > http://support.apple.com/kb/ht1430
Backing up, Updating and Restoring > http://support.apple.com/kb/HT1414
If you try all these Steps and you still have issues... Then a Visit to an Apple Store or AASP (Authorized Apple Service Provider) is the Next Step... Be sure to make an appointment first...

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Did you ever get an answer to this? I'm having the same issue.

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i have an iphone 4s and i over purchased by $15 from the appstore. in other words, i owe the appstore $15 . however, when i made a deposit of $20 into my card and tried to pay the appstore it says my payment method was declined. how can i fix this?

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I strongly recommend AIDA64 to show everything, temps, fans, chips, drivers and versions
http://www.aida64.com/ Windows has better tools to show you every service and knick and cranny
https://discussions.apple.com/thread/2769294
http://realitypod.com/category/hacks-and-cracks/mac-hacks-and-cracks/
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How to implement the schema validation with XSD in adapter module

Dear All,
I am trying to develop a EJB as the file adapter mudule.
Please guide me how to implement the schema validation of the source message with XSD.
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Red
Edited by: Grace Chien on Nov 19, 2008 8:23 AM

Hi Grace,
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To develop the adapter module for xml schema validation
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Schema Validation of Incoming Message
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I have different account ID's with my iphone and computer. I would like to standardise both to just the one. One of the ID's doesn't work, when I tried to list the second email with the preferred one a message telling me that this email is already in

I have different account ID's with my iphone and computer.
I would like to standardize both to just the one.
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While i am trying to save the existing record with same fields in cloud DTO using flex4 mxml app

hi,
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sorry but you question is not very clear...are you trying to show the item clicked on the datagrid on the input box? with an alert? you should look at "listevent" if thats the case?... sorry i just dont follow.
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How to specify a servlet mapping as the url pattern with in the security constraints

Hi ,
Weblogic 6.0 documentation says the following:-
Define which resources in the Web Application the security constraint applies to using the <url-pattern> element that is nested inside the <web-resource-collection> element. The <url-pattern> can refer to either a directory, filename or a <servlet-mapping>.
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Could any one let me know how to specify servlet mapping as the url pattern.
I tried various combination and it doesn't seem to work and any help in this regard will be greatly appreciated.
Thanks
kannan

The answer is posted here:
Unapproved User Flag in UME

Trying to implement the Observer pattern with a notify() method

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