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  • "Abstract static" method - how?

    - by polyglot
    There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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  • How can I pass a Context object to a thread on call

    - by Pentium10
    I have this code fragment: public static class ExportDatabaseFileTask extends AsyncTask<String, Void, Boolean> { private final ProgressDialog dialog = new ProgressDialog(ctx); protected void onPreExecute(); protected Boolean doInBackground(final String... args); protected void onPostExecute(final Boolean success); } I execute this thread as new ExportDatabaseFileTask().execute(); As you see I use a ctx as Context variable in the new ProgressDialog call, how do I pass a context to the call method? to this one: new ExportDatabaseFileTask().execute();*

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  • Hibernate Persistence problems with Bean Mapping (Dozer)

    - by BuffaloBuffalo
    I am using Hibernate 3, and having a particular issue when persisting a new Entity which has an association with an existing detached entity. Easiest way to explain this is via code samples. I have two entities, FooEntity and BarEntity, of which a BarEntity can be associated with many FooEntity: @Entity public class FooEntity implements Foo{ @Id private Long id; @ManyToOne(targetEntity = BarEntity.class) @JoinColumn(name = "bar_id", referencedColumnName = "id") @Cascade(value={CascadeType.ALL}) private Bar bar; } @Entity public class BarEntity implements Bar{ @Id private Long id; @OneToMany(mappedBy = "bar", targetEntity = FooEntity.class) private Set<Foo> foos; } Foo and Bar are interfaces that loosely define getters for the various fields. There are corresponding FooImpl and BarImpl classes that are essentially just the entity objects without the annotations. What I am trying to do is construct a new instance of FooImpl, and persist it after setting a number of fields. The new Foo instance will have its 'bar' member set to an existing Bar (runtime being a BarEntity) from the database (retrieved via session.get(..)). After the FooImpl has all of its properties set, Apache Dozer is used to map between the 'domain' object FooImpl and the Entity FooEntity. What Dozer is doing in the background is instantiating a new FooEntity and setting all of the matching fields. BarEntity is cloned as well via instantiation and set the FooEntity's 'bar' member. After this occurs, passing the new FooEntity object to persist. This throws the exception: org.hibernate.PersistentObjectException: detached entity passed to persist: com.company.entity.BarEntity Below is in code the steps that are occurring FooImpl foo = new FooImpl(); //returns at runtime a persistent BarEntity through session.get() Bar bar = BarService.getBar(1L); foo.setBar(bar); ... //This constructs a new instance of FooEntity, with a member 'bar' which itself is a new instance that is detached) FooEntity entityToPersist = dozerMapper.map(foo, FooEntity.class); ... session.persist(entityToPersist); I have been able to resolve this issue by either removing or changing the @Cascade annotation, but that limits future use for say adding a new Foo with a new Bar attached to it already. Is there some solution here I am missing? I would be surprised if this issue hasn't been solved somewhere before, either by altering how Dozer Maps the children of Foo or how Hibernate reacts to a detached Child Entity.

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  • Why does /**[newline] not always insert the Javadoc template including @param and @return in Eclipse

    - by Bas van den Broek
    I'm documenting code in Eclipse and have been using the /** followed by Enter alot to insert the Javadoc template. However this does not always work for some reason, it will create the template for writing comments but it won't automatically insert the @param and @return text. If I copy the exact same method to another class it will insert the full template. It would be a big help if anyone could tell me why it won't do this in some situations.

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  • Struts for IBM Application Server Toolkit

    - by Timbuck
    I'm looking to build a Struts 1.2.x application for Websphere, using IBM's Application Server Toolkit. Are there any plugins available for this toolkit (it is a version of Eclipse) that are known to help with this type of development? I am new to Struts so I will also be learning about the technology as I go along, but I want to make it as painless as possible. A web search has only brought up things such as "MyEclipse", which I can't use in the corporate environment.

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  • Iterate over a list and put data in hashmap

    - by sarah
    I am having a list where i need to loop over it and put its data in hashmap,i am using this approach for(int i=0;i<list.size();i++) { HashMap hMap=new HashMap(); hMap.put("Data", list); } But when i need to read the value from hMap i am doing in this way Collection c = hMap.values(); Iterator itr = c.iterator(); while(itr.hasNext()) { System.out.println("next val is--"+itr.next()); } next vali is--- is printed in com.bean.xyz@23032bc[id=1] format ,i need the exact data,how will i do this ?

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  • Queries with developing a Voice to Text Based Software

    - by harigm
    I am looking for any software which converts the voice to the text. I can get some software which can easily convert the english launguage voice to English text. But my intention is be it any language, whatever the system gets voice that should give the output in the text format in English. Is it possible to get this kind of software? If yes any open source available to help me to use this? If not, Is this feasible to develop this kind of software, Can any one guide how to and where to begin with? I am looking for windows based software

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  • KXML library Problem

    - by Hesham
    i'm working j2me with netbeans platform and i had a problem while i was trying to read a XML file and i added the library kxml.zip to my project's libraries and i used some of it's functions, there r no errors or red lines in the code, but the problem is that i cant run the project cos it come up with errors while compiling and all these errors are on the kxml functions, so any on can help me through this cos i really dont know what to do to make it run properly

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  • jsf and eclipse setup. Lib in Explorer is different than lib in tomcat. How come?

    - by user384706
    Hi, I am starter in JSF2.0, and I have a question related to Eclipse (I am using Helios). 1)I create a Dynamic Project 2)I add JSF project facet. 3)I choose JSF user library (I have created it using MyFaces) All ok so far. I notice though that in the Project Explorer in WebContent/WEB-INF/lib the lib directory is empty instead of having MyFaces jars. The application works fine though. I looked into this and the jars are actually being placed in the corresponding lib directory of the app deployed under wtpwebapps of the Tomcat instance of eclipse in the .pluggins directory. Ok, it works but IMHO it is incorrect to have the Project Explorer inconsistent with the directories actually deployed. I.e. lib is shown empty in Project Explorer but with jars under wtpwebapps. Am I wrong to dislike this inconsistency? Is this how it should work or am I doing something wrong in the way I am setting my project? Thanks!

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  • Can I have two names for the same variable?

    - by Roman
    The short version of the question: I do: x = y. Then I change x, and y is unchanged. What I want is to "bind" x and y in such a way that I change y whenever I change x. The extended version (with some details): I wrote a class ("first" class) which generates objects of another class ("second" class). In more details, every object of the second class has a name as a unique identifier. I call a static method of the first class with a name of the object from the second class. The first class checks if such an object was already generated (if it is present in the static HashMap of the first class). If it is already there, it is returned. If it is not yet there, it is created, added to the HashMap and returned. And then I have the following problem. At some stage of my program, I take an object with a specific name from the HashMap of the first class. I do something with this object (for example change values of some fields). But the object in the HashMap does not see these changes! So, in fact, I do not "take" an object from the HashMap, I "create a copy" of this object and this is what I would like to avoid.

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  • I have a feeling that adding fields marked with @Transient annotation to entity is very bug-prone. A

    - by Roman
    I have some philosophical feeling that adding to an entity fields which doesn't mapped to the DB is a wrong way of solving problems. But are there any concrete situations where using @Transient fields leads to implicit and hard fixing problems? For example, is it possible that adding/removing 2nd level cache will break our app when there are @Transient fields in our entities?

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  • Solr; What does this mean?

    - by Camran
    At the end of the README.txt file which is located in the example directory under solr, I find this line: NOTE: This Solr example server references SolrCell jars outside of the server directory with statements in the solrconfig.xml. If you make a copy of this example server and wish to use the ExtractingRequestHandler (SolrCell), you will need to copy the required jars into solr/lib or update the paths to the jars in your solrconfig.xml What does this mean? Do I have to make some adjustment before uploading solr to my server? Also, if you know, what is Solr-nightly:s difference to regular solr? The tutorial states "solr-nightly.zip" but on their download section I cant find it.

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  • How does Object Oriented Programming work?

    - by venom
    Hello, I am not sure about some things in OOP. If I have Class1, which has some private field, for example private Field field1, and make getField1 () { return field1; } then I have some class with constructor public Class2 (Field field) { someMethod(field); } And then I call constructor of Class2 in Class3 like: Class2 cl = new Class2(instanceOfClass1.getField1()); And now the question: Am I working with field1 of instanceOfClass1 in someMethod(field)?

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  • Jaxb to generate the XML directly to the OutputStream

    - by sonu
    Hi, I have a 500Mb csv file. I need to convert it into XML file. I am using the Jaxb to created the xml file. It is working fine for small amout of data. but for large amout of data like 300 mb it is throwing out of memory exception. Can anyone tell me that How can I create each element and write it into a file without creating the whole tree using the jaxb?" Thanks Sonu

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  • What features EJB3 bring and also how does EJB3 stack up with Spring Framework ?

    - by Rachel
    I have never worked on ejb, when I started programming Spring was already arrived and all my projects have been with Spring only, recently I had one interview and they wanted knowledge of EJB3.0 and so I want to know how does EJB3.0 stack up with Spring Framework and why many projects now a day are with Spring Framework and not with EJB3.0, do not quote me here as I can be wrong I would really appreciate if difference and benefits of using one over another could be explained from practical perspective.

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