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  • Use of 'super' keyword when accessing non-overridden superclass methods

    - by jonny
    I'm trying to get the hang of inheritance in Java and have learnt that when overriding methods (and hiding fields) in sub classes, they can still be accessed from the super class by using the 'super' keyword. What I want to know is, should the 'super' keyword be used for non-overridden methods? Is there any difference (for non-overridden methods / non-hidden fields)? I've put together an example below. public class Vehicle { public int tyreCost; public Vehicle(int tyreCost) { this.tyreCost = tyreCost; } public int getTyreCost() { return tyreCost; } } and public class Car extends Vehicle { public int wheelCount; public Vehicle(int tyreCost, int wheelCount) { super(tyreCost); this.wheelCount = wheelCount; } public int getTotalTyreReplacementCost() { return getTyreCost() * wheelCount; } } Specifically, given that getTyreCost() hasn't been overridden, should getTotalTyreReplacementCost() use getTyreCost(), or super.getTyreCost() ? I'm wondering whether super should be used in all instances where fields or methods of the superclass are accessed (to show in the code that you are accessing the superclass), or only in the overridden/hidden ones (so they stand out).

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  • IntelliJ Doesn't Notice Changes in Interface

    - by yar
    [I've decided to give IntelliJ another go (to replace Eclipse), since its Groovy support is supposed to be the best. But back to Java...] I have an Interface that defines a constant public static final int CHANNEL_IN = 1; and about 20 classes in my Module that implement that interface. I've decided that this constant was a bad idea so I did what I do in Eclipse: I deleted the entire line. This should cause the Project tree to light up like a Christmas tree and all classes that implement that interface and use that constant to break. Instead, this is not happening. If I don't actually double-click on the relevant classes -- which I find using grep -- the module even builds correctly (using Build - Make Module). If I double-click on a relevant class, the error is shown both in the Project Tree and in the Editor. I am not able to replicate this behavior in small tests, but in large modules it works (incorrectly) this way. Is there some relevant setting in IntelliJ for this?

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  • Is there any other way of using signed applets

    - by 640KB
    Hi There, If I want to deploy high privileged applets they need to be signed. For that a certificate is created and then a jar file is signed with a jarsigner. After that in the HTML code one has to specify code,codebase AND archive (jar) which we signed before. However I wrote a servlet which acts as two things: it sits at the URL pointed by the codebase and serves class bytecode to the applet. The same servlet also uses serialization to communicate with the applet whereby whenever the applet gets a class it does not know it goes to the codebase which ends up back at the servlet. Almost like a mini RMI setup but simpler. I hope you can see the power in this. Unfortunately for signed applets one needs the archive. Now the servlet is also able to load a Certificate object and can send it to the applet too. So here is the setup: At one point the applet receives class bytecode and it also has the Certificate. It would be nice if the applet could instantiate all received classes using that certificate (otherwise code from jar is signed and outside is not which prompts nasty messages to the user). So my question to you fine Java aficionados: Would there by any way for me to use the bytecode data and the Certificate to instantiate the class as a signed object so that the plugin pops the Security dialog, accepts teh certificate and elevates the object's privileges. What I could find is that the there is a class CodeSource that accepts codebase URL and certificate and is essential to the signing process. What I am not sure is how one could intercept the class loading inside applets to install additional certificates not obtained through a JAR file via archive. What do you say? Thanks a bunch.

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  • Way to store a large dictionary with low memory footprint + fast lookups (on Android)

    - by BobbyJim
    I'm developing an android word game app that needs a large (~250,000 word dictionary) available. I need: reasonably fast look ups e.g. constant time preferable, need to do maybe 200 lookups a second on occasion to solve a word puzzle and maybe 20 lookups within 0.2 second more often to check words the user just spelled. EDIT: Lookups are typically asking "Is in the dictionary?". I'd like to support up to two wildcards in the word as well, but this is easy enough by just generating all possible letters the wildcards could have been and checking the generated words (i.e. 26 * 26 lookups for a word with two wildcards). as it's a mobile app, using as little memory as possible and requiring only a small initial download for the dictionary data is top priority. My first naive attempts used Java's HashMap class, which caused an out of memory exception. I've looked into using the SQL lite databases available on android, but this seems like overkill. What's a good way to do what I need?

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  • Streaming content to JSF UI

    - by Mark Lewis
    Hello, I was quite happy with my JSF app which read the contents of MQ messages received and supplied them to the UI like this: <rich:panel> <snip> <rich:panelMenuItem label="mylabel" action="#{MyBacking.updateCurrent}"> <f:param name="current" value="mylog.log" /> </rich:panelMenuItem> </snip> </rich:panel> <rich:panel> <a4j:outputPanel ajaxRendered="true"> <rich:insert content="#{MyBacking.log}" highlight="groovy" /> </a4j:outputPanel> </rich:panel> and in MyBacking.java private String logFile = null; ... public String updateCurrent() { FacesContext context=FacesContext.getCurrentInstance(); setCurrent((String)context.getExternalContext().getRequestParameterMap().get("current")); setLog(getCurrent()); return null; } public void setLog(String log) { sendMsg(log); msgBody = receiveMsg(moreargs); logFile = msgBody; } public String getLog() { return logFile; } until the contents of one of the messages was too big and tomcat fell over. Obviously, I thought, I need to change the way it works so that I return some form of stream so that no one object grows so big that the container dies and the content returned by successive messages is streamed to the UI as it comes in. Am I right in thinking that I can replace the work I'm doing now on a String object with a BufferedOutputStream object ie no change to the JSF code and something like this changing at the back end: private BufferedOutputStream logFile = null; public void setLog(String log) { sendMsg(args); logFile = (BufferedOutputStream) receiveMsg(moreargs); } public String getLog() { return logFile; }

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  • Axis2 SOAP Envelope Header Information

    - by BigZig
    I'm consuming a web service that places an authentication token in the SOAP envelope header. It appears (through looking at the samples that came with the WS WSDL) that if the stub is generated in .NET, this header information is exposed through a member variable in the stub class. However, when I generate my Axis2 java stub using WSDL2Java it doesn't appear to be exposed anywhere. What is the correct way to extract this information from the SOAP envelope header? WSDL: http://www.vbar.com/zangelo/SecurityService.wsdl C# Sample: using System; using SignInSample.Security; // web service using SignInSample.Document; // web service namespace SignInSample { class SignInSampleClass { [STAThread] static void Main(string[] args) { // login to the Vault and set up the document service SecurityService secSvc = new SecurityService(); secSvc.Url = "http://localhost/AutodeskDM/Services/SecurityService.asmx"; secSvc.SecurityHeaderValue = new SignInSample.Security.SecurityHeader(); secSvc.SignIn("Administrator", "", "Vault"); DocumentServiceWse docSvc = new DocumentServiceWse(); docSvc.Url = "http://localhost/AutodeskDM/Services/DocumentService.asmx"; docSvc.SecurityHeaderValue = new SignInSample.Document.SecurityHeader(); docSvc.SecurityHeaderValue.Ticket = secSvc.SecurityHeaderValue.Ticket; docSvc.SecurityHeaderValue.UserId = secSvc.SecurityHeaderValue.UserId; } } } The sample illustrates what I'd like to do. Notice how the secSvc instance has a SecurityHeaderValue member variable that is populated after a successful secSvc.SignIn() invocation. Here's some relevant API documentation regarding the SignIn method: Although there is no return value, a successful sign in will populate the SecurityHeaderValue of the security service. The SecurityHeaderValue information is then used for other web service calls.

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  • Using maven to distribute a swing application that can have each dependency individually tracked

    - by tms
    I'm moving my project to Maven and eventually OSGi. I currently distribute the project is a large Zip file with all the dependencies. Although my projects code is only 20% of the total package I have to redistribute all the dependency. With smaller independent modules this may be even less. Looking here on stack overflow it seems that to keep my current plan the maven-assembly-plugin should do the trick. I was considering having a base installer that would look at a XML manifest, then collect all the libraries that needed to be updated. This would mean that libraries that change occasionally would be downloaded less often. This also makes since for something like OSGi plugins (which could have independent release schedules). In essence I want my software to look and manage individual libraries, and download on demand (based on the manifest). I was wondering if there is a "maven way" of generating this Manifest and publishing all the libraries to a website? I believe the deploy life-cycle would do the second step. As an alternative, is there a OpenSource Java library that does this type of deployment? I don't want to embed Maven or something larger with the distributed code. The application is not for coders, the simpler the better, and the smaller the installer the better.

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  • getting java.lang.OutOfMemoryError exception while running a Midlet (using netbeans)

    - by Jeeka
    I am writing a Midlet(using Netbeans) which reads a file containing exactly 2400 lines (each line being 32 characters long) and (extract a part of each line) puts them in an array. I am doing the same for 11 such files( all files have exactly 2400 lines).The Midlet runs fine for reading 6 files and putting them in 6 arrays. However, the Midlet stops while doing it for the 7th file throwing the following exception: TRACE: , startApp threw an Exception java.lang.OutOfMemoryError (stack trace incomplete) java.lang.OutOfMemoryError (stack trace incomplete) I have tried the modifying the netbeans.conf file to increase the heap memory ( as suggested by many forums and blogs) but nothing works for me. Here are the parameters that i had modified in the netbeans.conf file: -J-Xss2m -J-Xms1024m -J-Xmx1024m -J-XX:PermSize=1024m -J-XX:MaxPermSize=1536m -J-XX:+UseConcMarkSweepGC -J-XX:+CMSClassUnloadingEnabled -J-XX:+CMSPermGenSweepingEnabled Can anyone please help me to get me out of this ! I badly need this to be sorted out ASAP ! Thanks in advance !

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  • make a thread which recieves values from other threads

    - by farteaga88
    This program in Java creates a list of 15 numbers and creates 3 threads to search for the maximum in a given interval. I want to create another thread that takes those 3 numbers and get the maximum. but i don't know how to get those values in the other thread. public class apple implements Runnable{ String name; int time, number, first, last, maximum; int[] array = {12, 32, 54 ,64, 656, 756, 765 ,43, 34, 54,5 ,45 ,6 , 5, 65}; public apple(String s, int f, int l){ name = s; first = f; last = l; maximum = array[0]; } public void run(){ try{ for(int i = first; i < last; i++ ) { if(maximum < array[i]) { maximum = array[i]; } } System.out.println("Thread"+ name + "maximum = " + maximum); }catch(Exception e){} } public static void main(String[] args){ Thread t1 = new Thread(new apple("1 ", 0, 5)); Thread t2 = new Thread(new apple("2 ", 5, 10 )); Thread t3 = new Thread(new apple("3 ", 10, 15)); try{ t1.start(); t2.start(); t3.start(); }catch(Exception e){} } }

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  • how to filter files from the root "classes" and "test-classes" folders in Eclipse?

    - by Kidburla
    I am using ClearCase in my application which generates a whole load of ".copyarea.db" files (one in every folder). These cause conflicts when publishing to Tomcat as Eclipse will bundle the "classes" and "test-classes" folders into one JAR (not sure why it does this - as there is no need to have test classes available on the application server). Any folders with the same names will have a separate .copyarea.db in the classes and test-classes branches. I managed to get around this problem in general by adding ".copyarea.db" to the Filtered resources on the Java->Compiler->Building->Output Folder preference page. This stops the file appearing in source output (package/class folders), the vast majority of cases. However there remains the problem of the root folder, i.e. "target/classes/.copyarea.db" and "target/test-classes/.copyarea.db". These files are not filtered as they are not part of the compile task. Just deleting the files manually doesn't help either, as Eclipse expects to find them and doesn't. How can I exclude these ".copyarea.db" files from the root "classes" and "test-classes" folders?

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  • Searching in an Arraylist

    - by Puchatek
    Currently I have two classes. A Classroom class and a School class. I would like to write a method in the School class public void showClassRoomDetails which would find the classroom details by only using the teacherName. e.g. teacherName = Daniel className = Science teacherName = Bob className = Maths so when I input Bob, it would print out Bob and Maths many, thanks public class Classroom { private String classRoomName; private String teacherName; public void setClassRoomName(String newClassRoomName) { classRoomName = newClassRoomName; } public String returnClassRoomName() { return classRoomName; } public void setTeacherName(String newTeacherName) { teacherName = newTeacherName; } public String returnTeacherName() { return teacherName; } } import java.util.ArrayList; public class School { private ArrayList<Classroom> classrooms; private String classRoomName; private String teacherName; public School() { classrooms = new ArrayList<Classroom>(); } public void addClassRoom(Classroom newClassRoom, String theClassRoomName) { classrooms.add(newClassRoom); classRoomName = theClassRoomName; } public void addTeacherToClassRoom(int classroomId, String TeacherName) { if (classroomId < classrooms.size() ) { classrooms.get(classroomId).setTeacherName(TeacherName); } } public void showClassRoomDetails { //loop System.out.println(returnClassRoomName); System.out.println(returnTeacherName); } }

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  • How can one convince a team to use a new technology (LinQ, MVC, etc )?

    - by Atomiton
    Obviously, it's easier to do with some developers, but I'm sure many of us are on teams that prefer the status quo. You know the type. You see some benefit in a piece of new technology and they prefer the tried and true methods. Try, for example, DBA/C# programmer the advantages of using LinQ ( not necessarily LinQ to SQL, just LinQ in general ). For example, When a project requirement is to be cross-platform... instead of thinking about how one can run Windows on a Mac through a VM Machine, introducing the idea of using relatively new Silverlight or creating it in Java ( as an option to look into ). I know most people don't like to be out of their comfort level, so it takes a bit of convincing, and not ALL new technology makes business sense... but how have you convinced your team to look at a new technology? What technologies have you successfully introduced to your workplace? What technologies do you think are hardest to introduce? ( I'm thinking paradigm-shifting ones, like MVC from WebForms... or new languages ) What strategies do you employ to make these new technologies appealing?

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  • Within an aray of objects can one create a new instance of an object at an index?

    - by David
    Here's the sample code: class TestAO { int[] x; public TestAO () { this.x = new int[5] ; for (int i = 0; i<x.length; i++) x[i] = i; } public static void main (String[]arg) { TestAO a = new TestAO (); System.out.println (a) ; TestAO c = new TestAO () ; c.x[3] = 35 ; TestAO[] Z = new TestAO[3] ; Z[0] = a ; Z[1] = (TestAO b = new TestAO()) ; Z[2] = c ; } } When i try to compile this i get an error message at the line Z[1] which reads as follows: TestAO.java:22: ')' expected Z[1] = (TestAO b = new TestAO()) ; ^ What i'm trying to do here is create an instance of the object TestAO that i want to be in that index within the assignment of the value at that index instead of creating the instance of the object outside of the array like i did with a. Is this legal and i'm just making some syntax error that i can't see (thus causing the error message) or can what i'm trying to do just not be done?

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  • Lost in dates and timezones

    - by Sebastien
    I'm working on an application that stores conferences with their start and end date. Up until now, I was developing in Belgium and my server is in France, so everything is in the same timezone, no problem. But today, I'm in San Francisco, my server is in France and I noticed I have a bug. I'm setting dates from a Flex client (ActionScript automatically adapts date display according to client local timezone, which is GMT-8 for me today. My server runs on Hibernate and MySQL in France (GMT+1). So when I look at my database using phpMyAdmin, I see a date set to "2010-06-07 00:00:01" but in my Flex client it displays "2010-06-06 15:00:01". Ultimately, what I want is that the dates are displayed in the local timezone of the event, which is the date I set it to. So when I'm in Belgium and I set the start date of an event to be "2010-06-07 00:00:01" I want to retrieve it that way. But I'm lost as to what layer adapts what. Is timezone stored in DATETIME MySQL columns (I can't see it in MySQL)? Does Hibernate to anything to it when it transfers it to java.lang.Date that has Timezone information? And ultimately, what is the best way to solve this mess?

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  • Looping over commits for a file with jGit

    - by Andy Jarrett
    I've managed to get to grips with the basics of jGit file in terms of connecting to a repos and adding, commiting, and even looping of the commit messages for the files. File gitDir = new File("/Users/myname/Sites/helloworld/.git"); RepositoryBuilder builder = new RepositoryBuilder(); Repository repository; repository = builder.setGitDir(gitDir).readEnvironment() .findGitDir().build(); Git git = new Git(repository); RevWalk walk = new RevWalk(repository); RevCommit commit = null; // Add all files // AddCommand add = git.add(); // add.addFilepattern(".").call(); // Commit them // CommitCommand commit = git.commit(); // commit.setMessage("Commiting from java").call(); Iterable<RevCommit> logs = git.log().call(); Iterator<RevCommit> i = logs.iterator(); while (i.hasNext()) { commit = walk.parseCommit( i.next() ); System.out.println( commit.getFullMessage() ); } What I want to do next is be able to get all the commit message for a single file and then be able revert the single file back to a specific reference/point in time.

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  • Is it safe to silently catch ClassCastException when searching for a specific value?

    - by finnw
    Suppose I am implementing a sorted collection (simple example - a Set based on a sorted array.) Consider this (incomplete) implementation: import java.util.*; public class SortedArraySet<E> extends AbstractSet<E> { @SuppressWarnings("unchecked") public SortedArraySet(Collection<E> source, Comparator<E> comparator) { this.comparator = (Comparator<Object>) comparator; this.array = source.toArray(); Collections.sort(Arrays.asList(array), this.comparator); } @Override public boolean contains(Object key) { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } private final Object[] array; private final Comparator<Object> comparator; } Now let's create a set of integers Set<Integer> s = new SortedArraySet<Integer>(Arrays.asList(1, 2, 3), null); And test whether it contains some specific values: System.out.println(s.contains(2)); System.out.println(s.contains(42)); System.out.println(s.contains("42")); The third line above will throw a ClassCastException. Not what I want. I would prefer it to return false (as HashSet does.) I can get this behaviour by catching the exception and returning false: @Override public boolean contains(Object key) { try { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } catch (ClassCastException e) { return false; } } Assuming the source collection is correctly typed, what could go wrong if I do this?

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  • Custom Swing component: questions on approach

    - by phatmanace
    Hi Folks, I'm trying to build a new java swing component, I realise that I might be able to find one that does what I need on the web, but this is partly an exercise for me to learn ow to do this. I want to build a swing component that represents a Gantt chart. it would be good (though not essential for people to be able to interact with it (e.g slide the the tasks around to adjust timings) it feels like the best approach for this is to subclass JComponent, and override PaintComponent() to 'draw a picture' of what the chart should look like, as opposed to doing something like trying to jam everything into a custom JTable. I've read a couple of books on the subject, and also looked at a few examples (most notably things like JXGraph) - but I'm curious about a few things When do I have to switch to using UI delegates, and when can I stick to just fiddling around in paintcomponent() to render what I want? if I want other swing components as sub-elements of my component (e.g I wanted a text box on my gantt chart) can I no longer use paintComponent()? can I arbitrarily position them within my Gantt chart, or do I have to use a normal swing layout manager many thanks in advance. -Ace

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  • Why I get this error in CXF

    - by Milan
    I want to make dynamic web service invoker in JSF with CXF. But when I load this simple code I get error. The code: JaxWsDynamicClientFactory dcf = JaxWsDynamicClientFactory.newInstance(); Client client = dcf.createClient("http://ws.strikeiron.com/IPLookup2?wsdl"); The error: No Factories configured for this Application. This happens if the faces-initialization does not work at all - make sure that you properly include all configuration settings necessary for a basic faces application and that all the necessary libs are included. Also check the logging output of your web application and your container for any exceptions! If you did that and find nothing, the mistake might be due to the fact that you use some special web-containers which do not support registering context-listeners via TLD files and a context listener is not setup in your web.xml. A typical config looks like this; org.apache.myfaces.webapp.StartupServletContextListener Caused by: java.lang.IllegalStateException - No Factories configured for this Application. This happens if the faces-initialization does not work at all - make sure that you properly include all configuration settings necessary for a basic faces application and that all the necessary libs are included. Also check the logging output of your web application and your container for any exceptions! If you did that and find nothing, the mistake might be due to the fact that you use some special web-containers which do not support registering context-listeners via TLD files and a context listener is not setup in your web.xml. A typical config looks like this; org.apache.myfaces.webapp.StartupServletContextListener Any Idea how to solve the problem?

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  • Need help implementing this algorithm with map Hadoop MapReduce

    - by Julia
    Hi all! i have algorithm that will go through a large data set read some text files and search for specific terms in those lines. I have it implemented in Java, but I didnt want to post code so that it doesnt look i am searching for someone to implement it for me, but it is true i really need a lot of help!!! This was not planned for my project, but data set turned out to be huge, so teacher told me I have to do it like this. EDIT(i did not clarified i previos version)The data set I have is on a Hadoop cluster, and I should make its MapReduce implementation I was reading about MapReduce and thaught that i first do the standard implementation and then it will be more/less easier to do it with mapreduce. But didnt happen, since algorithm is quite stupid and nothing special, and map reduce...i cant wrap my mind around it. So here is shortly pseudo code of my algorithm LIST termList (there is method that creates this list from lucene index) FOLDER topFolder INPUT topFolder IF it is folder and not empty list files (there are 30 sub folders inside) FOR EACH sub folder GET file "CheckedFile.txt" analyze(CheckedFile) ENDFOR END IF Method ANALYZE(CheckedFile) read CheckedFile WHILE CheckedFile has next line GET line FOR(loops through termList) GET third word from line IF third word = term from list append whole line to string buffer ENDIF ENDFOR END WHILE OUTPUT string buffer to file Also, as you can see, each time when "analyze" is called, new file has to be created, i understood that map reduce is difficult to write to many outputs??? I understand mapreduce intuition, and my example seems perfectly suited for mapreduce, but when it comes to do this, obviously I do not know enough and i am STUCK! Please please help.

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  • What good open source programs exist for fuzzing popular image file types?

    - by JohnnySoftware
    I am looking for a free, open source, portable fuzzing tool for popular image file types that is written in either Java, Python, or Jython. Ideally, it would accept specifications for the fuzzable fields using some kind of declarative constraints. Non-procedural grammar for specifying constraints are greatly preferred. Otherwise, might as well write them all in Python or whatever. Just specifying ranges of valid values or expressions for them. Ideally, it would support some kind of generative programming to export the fuzzer into various programming languages to suit cases where more customization was required. If it supported a direct-manipulation GUI for controlling parameter values and ranges, that would be nice too. The file formats that should be supported are: GIF JPEG PNG So basically, it should be sort of a toolkit consisting of ready-to-run utility, a framework or library, and be capable of generating the fuzzed files directly as well as from programs it generates. It needs to be simple so that test images can be created quickly. It should have a batch capability for creating a series of images. Creating just one at a time would be too painful. I do not want a hacking tool, just a QA tool. Basically, I just want to address concerns that it is taking too long to get commonplace image rendering/parsing libraries stable and trustworthy.

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  • Invoking a method overloaded where all arguments implement the same interface

    - by double07
    Hello, My starting point is the following: - I have a method, transform, which I overloaded to behave differently depending on the type of arguments that are passed in (see transform(A a1, A a2) and transform(A a1, B b) in my example below) - All these arguments implement the same interface, X I would like to apply that transform method on various objects all implementing the X interface. What I came up with was to implement transform(X x1, X x2), which checks for the instance of each object before applying the relevant variant of my transform. Though it works, the code seems ugly and I am also concerned of the performance overhead for evaluating these various instanceof and casting. Is that transform the best I can do in Java or is there a more elegant and/or efficient way of achieving the same behavior? Below is a trivial, working example printing out BA. I am looking for examples on how to improve that code. In my real code, I have naturally more implementations of 'transform' and none are trivial like below. public class A implements X { } public class B implements X { } interface X { } public A transform(A a1, A a2) { System.out.print("A"); return a2; } public A transform(A a1, B b) { System.out.print("B"); return a1; } // Isn't there something better than the code below??? public X transform(X x1, X x2) { if ((x1 instanceof A) && (x2 instanceof A)) { return transform((A) x1, (A) x2); } else if ((x1 instanceof A) && (x2 instanceof B)) { return transform((A) x1, (B) x2); } else { throw new RuntimeException("Transform not implemented for " + x1.getClass() + "," + x2.getClass()); } } @Test public void trivial() { X x1 = new A(); X x2 = new B(); X result = transform(x1, x2); transform(x1, result); }

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  • Hibernate collection mapping Problem

    - by Geln Yang
    Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database.

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  • Object equality in context of hibernate / webapp

    - by bert
    How do you handle object equality for java objects managed by hibernate? In the 'hibernate in action' book they say that one should favor business keys over surrogate keys. Most of the time, i do not have a business key. Think of addresses mapped to a person. The addresses are keeped in a Set and displayed in a Wicket RefreshingView (with a ReuseIfEquals strategy). I could either use the surrogate id or use all fields in the equals() and hashCode() functions. The problem is that those fields change during the lifetime ob the object. Either because the user entered some data or the id changes due to JPA merge() being called inside the OSIV (Open Session in View) filter. My understanding of the equals() and hashCode() contract is that those should not change during the lifetime of an object. What i have tried so far: equals() based on hashCode() which uses the database id (or super.hashCode() if id is null). Problem: new addresses start with an null id but get an id when attached to a person and this person gets merged() (re-attached) in the osiv-filter. lazy compute the hashcode when hashCode() is first called and make that hashcode @Transitional. Does not work, as merge() returns a new object and the hashcode does not get copied over. What i would need is an ID that gets assigned during object creation I think. What would be my options here? I don't want to introduce some additional persistent property. Is there a way to explicitly tell JPA to assign an ID to an object? Regards

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  • Eclipse cannot find existing project in build path

    - by PNS
    Here is probably one of the idiosyncrasies of Eclipse and its handling of build paths, which cannot be fixed despite all sorts of workarounds tested so far. The issue relates to a workspace of several projects, each of which compiles into its own JAR. Dependencies among the projects are resolved by adding the relevant ones to the build path (no Maven or other external tool or plugin is used), via Project -> Properties -> Java Build Path -> Projects Among all these projects, a couple (say, com.example.p1 and com.example.p2) refuse to recognize a third (and simple) one (say, com.example.p3), while all other projects do. So, although P3 is added to the build path, all related classes from P3 are imported properly and the source code of each such class is accessible by hitting F3, Eclipse keeps complaining that The import com.example.p3 cannot be resolved and SomeClass cannot be resolved to a type where com.example.p3.SomeClass is one of the P3 classes. If instead of the P3 project I put its compiled JAR in the build path, the issue disappears. However, code in P3 changes frequently and it is a time waste to keep compiling and refreshing the workspace so that the change is picked up, not to mention that this should not happen in an IDE anyway (and it does not for the other projects using P3). Among the workarounds tried are things like: Removing and adding again P1, P2, P3 Cleaning up and recompiling everything Checking whether any other project loads the P3 JAR Putting P3 at the top of the Eclipse build path "Order and Export" list Using the "Fix project setup" suggestion of Eclipse (available when hovering the mouse over the red-underlined-error compilation line). Actually, this option offers adding to the build path either P3 or its JAR, but if P3 is added, the issue reappears. Any ideas?

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  • How can I go through a Set in JSP? (Hibernate Associations)

    - by Parris
    Hi All, So I am pretty new to JSP. I have tried this a few ways. Ways that would make sense in PHP or automagicy frameworks... I am probably thinking too much in fact... I have a hibernate one to many association. That is class x has many of class y. In class x's view.jsp. I would like to grab all of class y, where the foreign key of y matches the primary key of x and display them. It seems that hibernate properly puts this stuff into a set. Now, the question is how can I iterate through this set and then output it's contents... I am kind of stumped here. I tried to write a scriptlet, <% java.util.Iterator iter = aBean.getYs().iter(); // aBeans is the bean name // getYs would return the set and iter would return an iterator for the set while(iter.hasNext) { model.X a = new iter.next() %> <h1><%=a.getTitle()%></h1> <% } %> It would seem that that sort of thing should work? Hmmmmmm

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