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  • Volatile keyword

    - by Tiyoal
    Say I have two threads and an object. One thread assigns the object: public void assign(MyObject o) { myObject = o; } Another thread uses the object: public void use() { myObject.use(); } Does the variable myObject have to be declared as volatile? I am trying to understand when to use volatile and when not, and this is puzzling me. Is it possible that the second thread keeps a reference to an old object in its local memory cache? If not, why not? Thanks a lot.

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  • jsf custom control strange behaviour

    - by Cristian Boariu
    hi, I have a jsf custom control which contains this: <rich:column> <c:if test="#{not empty columnTitle}"> <f:facet name="header"> <rich:spacer/> </f:facet> </c:if> <s:link view="#{view}" value="#{messages['edit']}" propagation="#{propagation}"> <f:param name="${paramName}" value="${paramValue}"/> </s:link> &#160; <h:commandLink action="#{entityHome.removeMethodName(entity)}" value="#{messages['remove']}"/> </rich:column> You see that command link action. I want it to call an action like this: action="#{documentHome.removeProperty(property)"} Well, in order to do this i call the control like: <up:columnDetails view="/admin/property.xhtml" columnTitle="yes" entity="#{property}" paramValue="#{property.propertyId}" propagation="nest" entityHome="documentHome" removeMethodName="removeProperty"/> So, i hardcode entityHome and removeMethodName. Well an error is firing. Caused by javax.servlet.ServletException with message: "#{entityHome.removeMethodName(entity)}: javax.el.MethodNotFoundException It seems that it cannot interpret "removeMethodName". If i print entityHome or removeMethodName it correctly shows the values i pass. But i think jsf has an error like not beeing able to "believe" that after an object.something, that something can be a parameter... Can anyone guide me...?

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  • Best practice when removing entity regarding mappedBy collections?

    - by Daniel Bleisteiner
    I'm still kind of undecided which is the best practice to handle em.remove(entity) with this entity being in several collections mapped using mappedBy in JPA. Consider an entity like a Property that references three other entities: a Descriptor, a BusinessObject and a Level entity. The mapping is defined using @ManyToOne in the Property entity and using @OneToMany(mappedBy...) in the other three objects. That inverse mapping is defined because there are some situations where I need to access those collections. Whenever I remove a Property using em.remove(prop) this element is not automatically removed from managed entities of the other three types. If I don't care about that and the following page load (webapp) doesn't reload those entities the Property is still found and some decisions might be taken that are no longer true. The inverse mappings may become quite large and though I don't want to use something like descriptor.getProperties().remove(prop) because it will load all those properties that might have been lazy loaded until then. So my currently preferred way is to refresh the entity if it is managed: if (em.contains(descriptor)) em.refresh(descriptor) - which unloads a possibly loaded collection and triggers a reload upon the next access. Is there another feasible way to handle all those mappedBy collections of already loaded entites?

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  • Returning and instance of a Class given its .class (MyClass.class)

    - by jax
    I have an enum that will hold my algorithms. I cannot instantiate these classes because I need the application context which is only available once the application has started. I want to load the class at runtime when I choose by calling getAlgorithm(Context cnx). How do I easily instantiate a class at runtime given its .class (and my constructor takes arguments)? All my classes are subclasses of Algorithm. public enum AlgorithmTypes { ALL_FROM_9_AND_LAST_FROM_10_ID(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), ALL_FROM_9_AND_LAST_FROM_10_CURRENCY_ID(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), DIVIDE_BY_9_LESS_THAN_100(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), TABLES_BEYOND_5_BY_5(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class); private Class<? extends Algorithm> algorithm; AlgorithmTypes(Class<? extends Algorithm> c) { algorithm = c; } public Algorithm getAlgorithm(Context cnx) { return //needs to return the current algoriths constructor which takes the Context Algorithm(Context cnx); } }

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  • What GC parameters is a JVM running with?

    - by skaffman
    I'm still investigating issues I have with GC tuning (see prior question), which involves lots of reading and experimentation. Sun Java5+ JVMs attempt to automatically select the optimal GC strategy and parameters based on their environment, which is great, but I can't figure out how to query the running JVM to find out what those parameters are. Ideally, I'd like to see what values of the various GC-related -XX options are being used, as selected automatically by the VM. If I had that, I could have a baseline to begin tweaking. Anyone know to recover these values from a running VM?

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  • How to raise an action picker with options of Send to via sms, email, etc.

    - by Pentium10
    I've seen in applications a popup that prompts me what I do want to do with a text. I am prompted to choose from Send by SMS, Send by Email, Send by Bluetooth, Send by Fring etc. How do I make such a popup, it seamed to be automatically built? Also how do I tell what message to use? And if needed how do I tell who the contact is? Maybe chooses the options based on the contact, (if has email, show email)

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  • multiplying all elements in an array by an outside number?

    - by prodo
    I need to multiple all the values in an array by 3000 which in turn would create a new array that I will use to subtract from another array. I've tried to create a separate method that would do that for me but all I got back in the multiplied array was a bunch of numbers and symbols strangely? here is the code that I wrote public static void main(String[] args) { int numberOfTaxpayers = Integer.parseInt(JOptionPane.showInputDialog("Enter how many users you would like to calculate taxes for: "); int[] usernumChild = new int[numberOfTaxPayers]; for (int i = 0; i < usernumChild.length; i++) { usernumChild[i] = Integer.parseInt(JOptionPane.showInputDialog("Enter number of children for user "+ (i+1) +": ")); }//this for loop finds out the number of children per user so we can later multiply each input by 3000 to create an array that determine dependency exemption for each user int[] depndExemp = multiply(usernumChild, 3000);//this was the calling of the multiply method... somewhere here is the error!! }//end main method public static int[] multiply(int[] children, int number) { int array[] = new int[children.length]; for( int i = 0; i < children.length; i++) { children[i] = children[i] * number; }//end for return array; }//this is the method that I was shown in a previous post on how to create return an array in this the dependency exemption array but when I tested this by printing out the dependency array all I received were a jumble of wrong numbers.

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  • Code example with annotation in JavaDoc

    - by John
    Hello, my JavaDoc doesn't work when I have a code example with an annotation. Any suggestions? /** * <pre> * public class Demo { * @DemoAnnotation * public void demoMethod() { * } * } * </pre> */ @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.METHOD}) public @interface DemoAnnotation {

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  • new Integer vs valueOf

    - by LB
    Hi, I was using Sonar to make my code cleaner, and it pointed that I'm using new Integer(1) instead of Integer.valueOf(1). Because it seems that valueOf does not instantiate a new object so is more memory-friendly. How can valueOf not instantiate a new object ? How does it work ? Is this true for all integers ? thanks.

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  • Making html tags selectable in GWT

    - by Zoja
    I'm trying to display an html source ( without interpretation ) and I'd like all the nodes to be selectable (p, div, etc..). Something like in firebug where if I click on a node I can get it's properties. Does anybody have an idea how to do that or where to start ?

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  • Find all numbers that appear in each of a set of lists

    - by Ankur
    I have several ArrayLists of Integer objects, stored in a HashMap. I want to get a list (ArrayList) of all the numbers (Integer objects) that appear in each list. My thinking so far is: Iterate through each ArrayList and put all the values into a HashSet This will give us a "listing" of all the values in the lists, but only once Iterate through the HashSet 2.1 With each iteration perform ArrayList.contains() 2.2 If none of the ArrayLists return false for the operation add the number to a "master list" which contains all the final values. If you can come up with something faster or more efficient, funny thing is as I wrote this I came up with a reasonably good solution. But I'll still post it just in case it is useful for someone else. But of course if you have a better way please do let me know.

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  • AJAX Problem - No response text in FireFox, but ok in IE

    - by Taiba
    Hi, I am making a simple AJAX call to an external site. It works ok in IE, but in Firefox, not response text is returned. I think it might have something to do with the response being "chunked", but I'm not sure. Any ideas? Thanks. function loadXMLDoc() { var xmlhttp; var urlString = "http://drc.edeliver.com.au/ratecalc.asp?Pickup_Postcode=6025&Destination_Postcode=6055&Country=AU&Weight=100&Service_Type=STANDARD&Length=100&Width=100&Height=100&Quantity=2"; if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4) { window.alert(xmlhttp.responseText); } } xmlhttp.open("GET", urlString, true); xmlhttp.send(); }

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  • Why is the output like this?

    - by javatechi
    class another { public void method(Object o) { System.out.println("This is in method which takes object"); } public void method(String s) { System.out.println("This is method which takes string"); } } public class NewClass { public static void main(String args[]) { another an = new another(); an.method(null); } } When I try to execute this, I get This is method which takes string as the output. Why not "This is in method which takes object"? Object can also be null and string can also be null, why doesn't it invoke first method?

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  • Finding the specific type held in an ArrayList<Object> (ie. Object = String, etc.)

    - by Christopher Griffith
    Say I have an ArrayList that I have cast to an ArrayList of objects. I know that all the objects that were in the ArrayList I cast were of the same type, but not what the type was. Now, if the ArrayList is not empty, I could take one of the objects in it and use the instanceof operator to learn what the actual type is. But what of the case where the ArrayList is empty? How do I determine what type Object actually is then? Is it possible?

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  • jaxb: How can I bind nested element

    - by user368532
    There is my xml: <parent> <children> <child>1</child> <child>2</child> </children> </parent> I want to have the following Parent class: @XmlRootElement Parent{ @XmlElement(name="children/child") List<Child> children; } I don't want to have class for element 'children'. How should I map field children ?

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  • Join data from two Lists into one object

    - by Petr Mensik
    I ran into following situation and I am wondering about best solution. Let's say I have List<Object1> and List<Object2>, these lists are result of two separated queries. Both of them have the same size and there is relationship 1:1 between elements in the lists based on ID. I know that best solution would be fetching data in one DB query but that's possible right now. So my question is, what is the best way to join these lists into let's say List<Object3>?

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  • Automatically Add a Prefix to Column Names for @Embeddable Classes

    - by VeeArr
    I am developing a project in which I am persisting some POJOs by adding Hibernate annotations. One problem I am running into is that code like this fails, as Hibernate tries to map the sub-fields within the Time_T onto the same column (i.e. startTime.sec and stopTime.sec both try to map to the colum sec, causing an error). @Entity public class ExampleClass { @Id long eventId; Time_T startTime; Time_T stopTime; } @Embeddable public class Time_T { int sec; int nsec; } As there will be many occurrences like this throughout the system, it would be nice if there was an option to automatically append a prefix to the column name (e.g. make the columns be startTime_sec, startTime_nsec, stopTime_sec, stopTime_nsec), without having to apply overrides on a per-field basis. Does Hibernate have this capability, or is there any other reasonable work-around?

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