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  • ServiceLoader double iterator issues

    - by buge
    Is this a known issue? I had trouble finding any search results. When iterating over a ServiceLoader while an iteration already is in progress, the first iteration will be aborted. For example, assuming there are at least two implementations of Foo, the following code will fail with an AssertionError: ServiceLoader<Foo> loader = ServiceLoader.load(Foo.class); Iterator<Foo> iter1 = loader.iterator(); iter1.next(); Iterator<Foo> iter2 = loader.iterator(); while (iter2.hasNext()) { iter2.next(); } assert iter1.hasNext(); This only seems to occur, if the second iterator really terminates. The code will succeed in this variation for example: ServiceLoader<Foo> loader = ServiceLoader.load(Foo.class); Iterator<Foo> iter1 = loader.iterator(); iter1.next(); Iterator<Foo> iter2 = loader.iterator(); iter2.next(); assert iter1.hasNext(); Is this a bug or a feature? :p Is there a ticket for this already anywhere?

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  • Project Euler #3

    - by Alex
    Question: The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143? I found this one pretty easy, but running the file took an extremely long time, it's been going on for a while and the highest number I've got to is 716151937. Here is my code, am I just going to have a wait or is there an error in my code? //User made class public class Three { public static boolean checkPrime(long p) { long i; boolean prime = false; for(i = 2;i<p/2;i++) { if(p%i==0) { prime = true; break; } } return prime; } } //Note: This is a separate file public class ThreeMain { public static void main(String[] args) { long comp = 600851475143L; boolean prime; long i; for(i=2;i<comp/2;i++) { if(comp%i==0) { prime = Three.checkPrime(i); if(prime==true) { System.out.println(i); } } } } }

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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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  • 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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  • 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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  • 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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  • how to add list to button

    - by priya
    hi... how to add a list to a button.. for example if i have four button like classic, western, jazz,pop.if i click classic button i should get subtitle .or if i click western i should get sub title... so how to creat

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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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  • Redirects in Glassfish (adding trailing slash)

    - by echox
    Is it possible to add a trailing slash to the default context of an application? Example: http://www.uri.com/foo -> http://www.uri.com/foo/ I added the following redirect to the server properties: redirect_1: from=/foo url-prefix=/foo/ and this ends up in a loop... Several other configurations also didn't work :-/ I'm using glassfish v2.1-b60e.

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  • What Design Pattern is this?

    - by 01
    I know that everything we do in programming can be described as design pattern(even abstract method has design pattern called template method) public class Guicer extends AbstractModule { private static Injector injector = Guice.createInjector(new Guicer()); public static void setInjector(Injector injector) { Guicer.injector = injector; } public static T getInstance(Class c) { return injector.getInstance(c); } @Override protected void configure() { } } What design patterns are used in this code?

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  • Keeping track of threads when creating them recursively

    - by 66replica
    I'm currently working on some code for my Programming Languages course. I can't post the code but I'm permitted to talk about some high level concepts that I'm struggling with and receive input on them. Basically the code is a recursive DFS on a undirected graph that I'm supposed to convert to a concurrent program. My professor already specified that I should create my threads in the recursive DFS method and then join them in another method. Basically, I'm having trouble thinking of how I should keep track of the threads I'm creating so I can join all of them in the other method. I'm thinking an array of Threads but I'm unsure how to add each new thread to the array or even if that's the right direction.

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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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  • 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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  • 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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  • Merge object from list by comparing one value

    - by Bala
    I have two List of Objects (one is master list and other is error list) and if there is a match of one value when compared two lists then merge all other error list values into mast list value (only one object). Other than iterating is there any other way to compare a value and then merge that object. Object is a Value object with some setters and getters. Appreciate your help. List<OrderVO> masterList; List<OrderVO> errorList; If errorList.OrderVO.getOrderID = masterList.OrderVO.getOrderID then masterList.OrderVO.merge(errorList.OrderVO) or copy all values of masterList.OrderVO.copy(errorList.OrderVO). Hoper this is clear

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