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  • data structure for counting frequencies in a database table-like format

    - by user373312
    i was wondering if there is a data structure optimized to count frequencies against data that is stored in a database table-like format. for example, the data comes in a (comma) delimited format below. col1, col2, col3 x, a, green x, b, blue ... y, c, green now i simply want to count the frequency of col1=x or col1=x and col2=green. i have been storing the data in a database table, but in my profiling and from empirical observation, database connection is the bottle-neck. i have tried using in-memory database solutions too, and that works quite well; the only problem is memory requirements and quirky init/destroy calls. also, i work mainly with java, but have experience with .net, and was wondering if there was any api to work with "tabular" data in a linq way using java. any help is appreciated.

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  • Are there any OSGi web service / SOAP clients out there?

    - by James Carr
    I'm looking for any webservice client that can be run inside an OSGi container and connect to a simple web service using SOAP, doesn't sound so hard does it? Oh, and it has to work under Java 1.5, so the JRE jax-ws wont be present. The problem is I've tried a few solutions now, and although each solution works in standard Java using it from within OSGi doesn't. the springsource JAX-WS bundles seem to have dependency issues the CXF bundles get me as far as calling the service, but then can seem to find the stub methods in the proxy Is there anyone out there who has successfully created an OSGi webservice client?

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  • Hibernate pluralization

    - by matiasf
    I have A MySQL database currently in production use for a CakePHP application A Java SE application accessing the same database via Hibernate, currently in development. I'm using the Netbeans "automigrate" feature to create the POJO classes and XML files (do I really need the XML files when using annotations?). As the schema is quite complex creating the tables manually is way too much work. Cake expects all DB tables to be pluralized (the Address class is automagically mapped to the addresses table). When running the Netbeans automigration it then does pluralization on the already pluralized table names (I'm getting Addresses.java and setAddresseses() methods). I know I'm asking for trouble running two very different data layers against the same database, but I'd like to know if it's possible to have Netbeans generating the POJO classes in singular form or if there is another (better) way to manage this.

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  • Is it acceptable to email an Interviewer after the interview?

    - by djhworld
    Yesterday I took part in an interview for a Java position in a company and one of the questions was Does Java pass by reference or by value? In the heat of the moment I (mistakenly) confidently said it passed by reference, possibly because I come from a C/C++ background. Unfortunately after the interview I'd realised my terrible mistake to my horror. So my question is this, is it acceptable for me to wait a few days and drop a quick email to recognise my mistake? Or should I just let this one lie?

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  • Problem persisting inheritance tree

    - by alaiseca
    I have a problem trying to map an inheritance tree. A simplified version of my model is like this: @MappedSuperclass @Embeddable public class BaseEmbedded implements Serializable { @Column(name="BE_FIELD") private String beField; // Getters and setters follow } @MappedSuperclass @Embeddable public class DerivedEmbedded extends BaseEmbedded { @Column(name="DE_FIELD") private String deField; // Getters and setters follow } @MappedSuperclass public abstract class BaseClass implements Serializable { @Embedded protected BaseEmbedded embedded; public BaseClass() { this.embedded = new BaseEmbedded(); } // Getters and setters follow } @Entity @Table(name="MYTABLE") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="TYPE", discriminatorType=DiscriminatorType.STRING) public class DerivedClass extends BaseClass { @Id @Column(name="ID", nullable=false) private Long id; @Column(name="TYPE", nullable=false, insertable=false, updatable=false) private String type; public DerivedClass() { this.embedded = new DerivedClass(); } // Getters and setters follow } @Entity @DiscriminatorValue("A") public class DerivedClassA extends DerivedClass { @Embeddable public static NestedClassA extends DerivedEmbedded { @Column(name="FIELD_CLASS_A") private String fieldClassA; } public DerivedClassA() { this.embedded = new NestedClassA(); } // Getters and setters follow } @Entity @DiscriminatorValue("B") public class DerivedClassB extends DerivedClass { @Embeddable public static NestedClassB extends DerivedEmbedded { @Column(name="FIELD_CLASS_B") private String fieldClassB; } public DerivedClassB() { this.embedded = new NestedClassB(); } // Getters and setters follow } At Java level, this model is working fine, and I believe is the appropriate one. My problem comes up when it's time to persist an object. At runtime, I can create an object which could be an instance of DerivedClass, DerivedClassA or DerivedClassB. As you can see, each one of the derived classes introduces a new field which only makes sense for that specific derived class. All the classes share the same physical table in the database. If I persist an object of type DerivedClass, I expect fields BE_FIELD, DE_FIELD, ID and TYPE to be persisted with their values and the remaining fields to be null. If I persist an object of type DerivedClass A, I expect those same fields plus the FIELD_CLASS_A field to be persisted with their values and field FIELD_CLASS_B to be null. Something equivalent for an object of type DerivedClassB. Since the @Embedded annotation is at the BaseClass only, Hibernate is only persisting the fields up to that level in the tree. I don't know how to tell Hibernate that I want to persist up to the appropriate level in the tree, depending on the actual type of the embedded property. I cannot have another @Embedded property in the subclasses since this would duplicate data that is already present in the superclass and would also break the Java model. I cannot declare the embedded property to be of a more specific type either, since it's only at runtime when the actual object is created and I don't have a single branch in the hierarchy. Is it possible to solve my problem? Or should I resignate myself to accept that there is no way to persist the Java model as it is? Any help will be greatly appreciated.

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  • floating constants in C

    - by Daziplqa
    Hi floks, I have a question concerning floating constants in C. In Java, the default type of floating point constants in double, so the following will causes a compilation error in java: float f = 100.0; // we either need to uses type case operator or put f at the end of the number constant. This is because the default floating-point constants are of type double and casting from double to float without type cast operator is an error, so we need either add a type case operator or put f at the end of the number. So, Why in C this doesn't produce an error, Is it because the default floating-point constants are of type float, or because the compiler do an implicit down-cast conversion (that doesn't requires type case operator in C)????

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  • Why should pop() take an argument?

    - by Stephano
    Quick background I'm a Java developer who's been playing around with C++ in my free/bored time. Preface In C++, you often see pop taking an argument by reference: void pop(Item& removed); I understand that it is nice to "fill in" the parameter with what you removed. That totally makes sense to me. This way, the person who asked to remove the top item can have a look at what was removed. However, if I were to do this in Java, I'd do something like this: Item pop() throws StackException; This way, after the pop we return either: NULL as a result, an Item, or an exception would be thrown. My C++ text book shows me the example above, but I see plenty of stack implimentations taking no arguments (stl stack for example). The Qustion How should one implement the pop function in C++? The Bonus Why?

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  • Is a function kind of like a static method?

    - by lkm
    I'm a java programmer and am trying to understand the difference between a method (java methods) and a function (such as in c++). I used to think that they are the same, just different naming conventions for different programming languages. But now that I know they are not, I am having trouble understanding the difference. I know that a method relates to an instance of a class and has access to class data (member variables), while a function does not (?). So is a function kind of like a static method? See here for explanations I read which led me to think this.

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  • Trouble with arraylist and stack

    - by helloman
    I am having trouble starting out this program, I am suppose to write a program that will create an ArrayList, asking the user for 10 numbers. Then this will be put into the Array. Then after the list is made navigate it and if a number is even remove it from the ArrayList and copy it to a stack of integers. import java.io.* ; import java.util.*; public class Test { public static void main(String[] args){ Scanner input = new Scanner (System.in); ArrayList<Integer> integers = new ArrayList<Integer>(); System.out.print ("Enter Number: \n"); for (int i = 0; i < 10; i++){ integers.add(input.nextInt()); } for (int i = 0; i < 10 ; i++){ if (i %2==0) } } }

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  • Use deployJava.js to check for/automatically install latest JRE version for web applet

    - by Pryo
    I'd like to use the deployJava.js tool to have Java automatically detect the currently installed JRE and install an updated version if necessary. My initial impression when reading about deployJava.js was that it would do this out of the box when you simply set a version number as a function parameter for the "runApplet" function. But this has never seemed to work. Is it even possible to do this, and if so, how? Here is my current code for launching my applet: <script type="text/javascript" src="https://www.java.com/js/deployJava.js"></script> <script type="text/javascript"> var attributes = {id:"applet", name:"TheApplet", code:"TheApplet"}; var parameters = {jnlp_href: "http://localhost/TheApplet.jnlp"}; deployJava.runApplet(attributes, parameters, "1.6.0_31"); </script> Thanks

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  • International JRE6 or JDK6 or reading a file in "cp037" encoding scheme

    - by Reddy
    I have been trying to read a file in "cp037" encoding scheme using JAVA. I able to read a file in basic encoding schemes like UTF-8, UTF16 etc...After a bit of research on the internet i came to know that we need charset.jar or international version of JRE be installed to support extended encoding schemes. Can anyone send me a link for international version of JRE6 or JDK6. or is there any better way that i could read a file in cp037 encoding scheme. P.S: cp037 is a character encoding scheme supported by IBM Mainframes. All i need is to display a file in windows, which is being generated on IBM Mainframes machine, using a java program. Thanks in advance for your help... :-)

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  • GWT Deserialisation of Persistent Entities (JPA)

    - by slartidan
    Hi everyone, I am currently developing Java/GWT-application which is hosted on a weblogic application server. I am using EJB3.0 with EclipseLink as persistence layer. Sadly my GWT has problems to deserialize persistent entities. It might be helpful for you to know, that I have the EclipseLink-Library in my classpath (including javax.persistence.Entity) am not recieving the persistence objects from a database or persistence-manager - I am creating the objects with standard java code use Eclipse IDE for Java EE Developers for development and deploying and I am compiling my GWT code with the GWT-Plugin (GWT 2.1.0) - my source code is split up in several projects am pretty sure, that the problems occures on client side, since the HTTP response of my server is the same in my working and in my not working example tried to patch javax.persistence.Entity and tried to include several libraries which included javax.persistence.Entity but nothing was helping In my server provides a list of instances of class SerialClass; the interface looks like this: public interface GreetingService extends RemoteService { List<SerialClass> greetServer(); } My onModuleLoad()-Method gets those instances and creates a browser-popup with the information: public void onModuleLoad() { GreetingServiceAsync server = (GreetingServiceAsync) GWT.create(GreetingService.class); server.greetServer(new AsyncCallback<List<SerialClass>>() { public void onFailure(Throwable caught) { } public void onSuccess(List<SerialClass> result) { String resultString = ""; try { for (SerialClass serial : result) { if (serial == null) { resultString += "null "; } else { resultString += ">" + serial.id + "< "; } } } catch (Throwable t) { Window.alert("failed to process"); } Window.alert("success:" + resultString); } }); } My server is looking like this: public class GreetingServiceImpl extends RemoteServiceServlet implements GreetingService { public List<SerialClass> greetServer() throws IllegalArgumentException { List<SerialClass> list = new ArrayList<SerialClass>(); for (int i = 0; i < 100; i++) { list.add(new SerialClass()); } return list; } } Case 1 = everything works fine I am using this SerialClass (either without any annotation, or with any annotation other than Entity - for example javax.persistence.PersistenceContext works fine): //@Entity public class SerialClass implements Serializable, IsSerializable { public int id = 4711; } The popup contains (as expected): success:>4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< >4711< The data sent over HTTP looks like this: //OK[4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,100,1,["java.util.ArrayList/3821976829","serial.shared.SerialClass/10650133"],0,6] Case 2 = its not working at all I am using this SerialClass: @Entity public class SerialClass implements Serializable, IsSerializable { public int id = 4711; } My popup contains (THIS IS MY PROBLEM): success:>2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null >2< null The data sent over HTTP looks like this (exactly the same!): //OK[4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,4711,2,100,1,["java.util.ArrayList/3821976829","serial.shared.SerialClass/10650133"],0,6] There is no suspicious logging output - neither on server, nor on client. All HTTP-responses have return code 200. My current workaround I am going to try to create transfer objects as a copy of my SerialClass - those transfer objects will look exactly the same, but will not have the @Entity annotation. Alternatively I could try to use the RequestFactory (thanks to @Hilbrand for the hint). I really don't know how to solve that problem and I'm really thankful about any suggestions, hints, tips, links, etc.

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  • How to access a XML file in a maven project so it stays available when packaged

    - by Manuel
    I currently started working on a maven web-app project that needs to be launched with the jetty:run-exploded goal for development/debugging in eclipse. Now, I have an XML file which contents I need to access at runtime. My problem is: where to put the file so that the code that does the reading works both in "exploded" and packaged (i.e. in the WAR) mode? Putting the file in src/main/java (so as to be in the classpath) won't cut it since maven filters out all non-java files on packaging. When the file is in src/main/resources, one mean would be to figure out the root path of the project (during eclipse development) and look into that directory - but this won't be the case anymore when the project will be packaged. Of course I could go into writing code that tries to read the file from both locations, but this seems rather cumbersome. Any suggestions?

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  • Keystore in PKCS12 format seems empty to keytool, but is read by Firefox?!

    - by hjh
    I have a problem with a keystore in pkcs12 format, which contains a private key I need to use to authenticate myself (using mutual authentication) to a remote SSL server. The keystore file can be read perfectly fine by Firefox, and when used, I can access the remote server without problems. However, my Java program does not work with the keystore file. And if I use keytool to list keys inside the file, it seems empty -- while it is clearly not! How can I get Java/keytool to see the private key inside the keystore?

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  • why can't I call .update on a MessageDigest instance

    - by Arthur Ulfeldt
    when i run this from the repl: (def md (MessageDigest/getInstance "SHA-1")) (. md update (into-array [(byte 1) (byte 2) (byte 3)])) I get: No matching method found: update for class java.security.MessageDigest$Delegate the Java 6 docs for MessageDigest show: update(byte[] input) Updates the digest using the specified array of bytes. and the class of (class (into-array [(byte 1) (byte 2) (byte 3)])) is [Ljava.lang.Byte; Am I missing something in the definition of update? Not creating the class I think I am? Not passing it the type I think I am?

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  • Unable to export runnable jar, launch configuration grayed out

    - by user13107
    I am not able to figure out how to export a runnable jar in eclipse. I have a java project (project A) (written by someone else) which when imported in Eclipse, I can click Build Project and it will create a projectName.jar file under bin/ directory. That jar file contains binary *.class files. This jar file is added as external library for another java project (project B) which I want to debug. But because all the class files are binary I'm not able to do line-by-line debugging. I tried exporting Runnable Jar in Eclipse, for that I have to select a Launch Configuration. But there is no main class in project A. (I recursively grepped for main and didn't find any). What can I do to export jar of project A that contains respective source code also (which will be used in line-by-line debugging)?

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  • What's causing "Unable to retrieve native address from ByteBuffer object"?

    - by r0u1i
    As a very novice Java programmer, I probably should not mess with that kind of things. Unfortunately, I'm using a library which have a method that accepts a ByteBuffer object and throws when I try to use it: Exception in thread "main" java.lang.NullPointerException: Unable to retrieve native address from ByteBuffer object Is it because I'm not using a non-direct buffer? edit: There's not a lot of my code there. The library I'm using is jNetPcap, and I'm trying to dump a packet to file. My code takes an existing packet, and extract a ByteBuffer out of it: byte[] bytes = m_packet.getByteArray(0, m_packet.size()); ByteBuffer buffer = ByteBuffer.wrap(bytes); Then it calls on of the dump methods of jNetPcap that takes a ByteBuffer.

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  • Gen folder disappearing in Eclipse Android project

    - by Adam Haile
    I'm just getting started developing for Android and I'm running into a weird problem. First off, I'm running Eclipse for Java devs v3.5.2 with the Android 2.1 SDK installed. Basically, whenever I do just about anything the "gen" (R.java, etc.) folder will just disappear from the project. I'm seen some people online say that it was still on the drive, just gone from the project listing in Eclipse, but in my case it is literally and completely gone. The only fix I've found is that if I refresh, then try to build, it gives an error and "gen" shows up in the project view (though it's not on the disk), then delete it from within the project, then Rebuild All and it will say that it cannot find it and is recreating it. Problem is, I have to do this every single time I want to build. There's got to be a fix for this.

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  • PHP Path issue running backticks/exec()

    - by Lee
    Hey all I'm trying to run a java jar file from the command line and within the the execution it gives a path. Withing this path their are spaces and this is causing the issue. ie $f = `java -jar /OCR/ocr.jar /Folder/Sub Folder/filetoocr.pdf /ocr/output.txt`; echo "<pre>$output</pre>"; If you can see the space in between the Sub Folder name causes the issue. By command line it would be (which works) java -jar /OCR/ocr.jar /Folder/Sub\ Folder/filetoocr.pdf /ocr/output.txt any suggestions how I can resolve this ?? Hope you can advise

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  • UseConcMarkSweepGC verbose gc output shows memory drops

    - by user1864747
    I have an application for which I have enabled GC logging. The heap appears to grow then takes a sudden drop, but does not log a Full GC. If there some startup parameter that I can enable that will show me what GC event is reducing the heap size? My environment: Linux 64-Bit, java 1.6.0_31, Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01, mixed mode) VM args: -server -Xms2560m -Xmx2560m -XX:+UseConcMarkSweepGC -XX:MaxPermSize=256m -XX:-PrintGC -XX: -PrintGCDetails -XX:-PrintGCTimeStamps -Xloggc:/xxxxx/gc.log -Dsun.rmi.dgc.client.gcInterval=86400000 -Dsun.rmi.dgc.server.gcInterval=86400000 3057.609: [GC 2397254K->2385777K(2619328K), 0.0572310 secs] 3058.898: [GC 2402801K->2391301K(2619328K), 0.0566620 secs] 3059.940: [GC 2408325K->2397156K(2619328K), 0.0534080 secs] 3059.995: [GC 2397265K(2619328K), 0.0069950 secs] 3065.635: [GC 2414180K->2404934K(2619328K), 0.0732700 secs] 3065.849: [GC 2419994K(2619328K), 0.1150630 secs] 3070.248: [GC 1593931K->1591825K(2619328K), 0.1084230 secs] 3072.440: [GC 1608552K->1606431K(2619328K), 0.0533140 secs] 3087.759: [GC 1623455K->1614544K(2619328K), 0.0215850 secs] What event is causing the heap to shrink between the output at 3065.849 and 3070.248? Is there a VM param that will log it? I tried adding -verbose:gc but that does not change the output.

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