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  • What's the most efficient way to load data from a file to a collection on-demand?

    - by Dan
    I'm working on a java project that will allows users to parse multiple files with potentially thousands of lines. The information parsed will be stored in different objects, which then will be added to a collection. Since the GUI won't require to load ALL these objects at once and keep them in memory, I'm looking for an efficient way to load/unload data from files, so that data is only loaded into the collection when a user requests it. I'm just evaluation options right now. I've also thought of the case where, after loading a subset of the data into the collection, and presenting it on the GUI, the best way to reload the previously observed data. Re-run the parser/Populate collection/Populate GUI? or probably find a way to keep the collection into memory, or serialize/deserialize the collection itself? I know that loading/unloading subsets of data can get tricky if some sort of data filtering is performed. Let's say that I filter on ID, so my new subset will contain data from two previous analyzed subsets. This would be no problem is I keep a master copy of the whole data in memory. I've read that google-collections are good and efficient when handling big amounts of data, and offer methods that simplify lots of things so this might offer an alternative to allow me to keep the collection in memory. This is just general talking. The question on what collection to use is a separate and complex thing. Do you know what's the general recommendation on this type of task? I'd like to hear what you've done with similar scenarios. I can provide more specifics if needed.

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  • Jersey, JAXB and getting an objectextending an abstract class as a parameter

    - by krajol
    I want to get an object as a parameter of a POST request. I got an abstract superclass that is called Promotion and subclasses Product and Percent. Here's how I try to get a request: @POST @Consumes(MediaType.APPLICATION_XML) @Produces(MediaType.APPLICATION_XML) @Path("promotion/") public Promotion createPromotion(Promotion promotion) { Product p = (Product) promotion; System.out.println(p.getPriceAfter()); return promotion; } and here's how I use JAXB in classes' definitions: @XmlRootElement(name="promotion") @XmlSeeAlso({Product.class,Percent.class}) public abstract class Promotion { //body } @XmlRootElement(name="promotion") public class Product extends Promotion { //body } @XmlRootElement(name="promotion") public class Percent extends Promotion { //body } So the problem now is when I send a POST request with a body like this: <promotion> <priceBefore>34.5</priceBefore> <marked>false</marked> <distance>44</distance> </promotion> and I try to cast it to Product (as in this case, fields 'marked' and 'distance' are from Promotion class and 'priceBefore' is from Product class) I get an Exception: java.lang.ClassCastException: Percent cannot be cast to Product. It seems like Percent is chosen as a 'default' subclass. Why is that and how can I get an object that is a Product?

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  • Can I add a spring mvc filter using jetty with a jar file?

    - by Juan Manuel
    I have a simple web application disguised as a java application (as in, it's a .jar instead of a .war), and I'd like to use a filter for my requests. If it was a .war, I could initialize it with a WebAppContext and specify a web.xml file where I'd have my filter declaration like this <filter> <filter-name>myFilter</filter-name> <filter-class>MyFilterClass</filter-class> </filter> <filter-mapping> <filter-name>myFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> However, I'm using a simple Context to initialize my application with Spring. Server server = new Server(8082); Context root = new Context(server, "/", Context.SESSIONS); DispatcherServlet dispatcherServlet = new DispatcherServlet(); dispatcherServlet.setContextConfigLocation("classpath:application-context.xml"); root.addServlet(new ServletHolder(dispatcherServlet), "/*"); server.start(); Is there a way to programmatically specify filters for the spring servlet, without using a web.xml file?

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  • Invoking different methods on threads

    - by Kraken
    I have a main process main. It creates 10 threads (say) and then what i want to do is the following: while(required){ Thread t= new Thread(new ClassImplementingRunnable()); t.start(); counter++; } Now i have the list of these threads, and for each thread i want to do a set of process, same for all, hence i put that implementation in the run method of ClassImplementingRunnable. Now after the threads have done their execution, i wan to wait for all of them to stop, and then evoke them again, but this time i want to do them serially not in parallel. for this I join each thread, to wait for them to finish execution but after that i am not sure how to evoke them again and run that piece of code serially. Can i do something like for(each thread){ t.reevoke(); //how can i do that. t.doThis(); // Also where does `dothis()` go, given that my ClassImplementingRunnable is an inner class. } Also, i want to use the same thread, i.e. i want the to continue from where they left off, but in a serial manner. I am not sure how to go about the last piece of pseudo code. Kindly help. Working with with java.

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  • Am I doing it right?

    - by LuckySlevin
    I have situation. I have to create a Sports Club system in JAVA. There should be a class your for keeping track of club name, president name and braches the club has. For each sports branch also there should be a class for keeping track of a list of players. Also each player should have a name, number, position and salary. So, I come up with this. Three seperate classes: public class Team { String clubName; String preName; Branch []branches; } public class Branch { Player[] players; } public class Player { String name; String pos; int salary; int number; } The problems are creating Branch[] in another class and same for the Player[]. Is there any simplier thing to do this? For example, I want to add info for only the club name, president name and branches of the club, in this situation, won't i have to enter players,names,salaries etc. since they are nested in each other. I hope i could be clear. For further questions you can ask.

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  • How do I send data between two computers over the internet

    - by Johan
    I have been struggling with this for the entire day now, I hope somebody can help me with this. My problem is fairly simple: I wish to transfer data (mostly simple commands) from one PC to another over the internet. I have been able to achieve this using sockets in Java when both computers are connected to my home router. I then connected both computers to the internet using two different mobile phones and attempted to transmit the data again. I used the mobile phones as this provides a direct route to the internet and if I use my router I have to set up port forwarding, at least, that is how I understand it. I think the problem lies in the method that I set up the client socket. I used: Socket kkSocket = new Socket(ipAddress, 3333); where ipAddress is the IP address of the computer running the server. I got the IP address by right-clicking on the connection, status, support. Is that the correct IP address to use or where can I obtain the address of the server? Also, is it possible to get a fixed name for my computer that I can use instead of entering the IP address, as this changes every time I connect to the internet using my mobile phone? Alternatively, are there better methods to solving my problem such as using http, and if so, where can I find more information about this? Thanks!

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  • Changing brightness in bufferedImage with DataBufferInt

    - by user2958025
    I must read some image and then I have to change brightness and contrast of this image I create main class and constructor where are panels, sliders and other stuff, I added changeListener to slider to take current value. My imagePanel is new Object of that class: public class Obrazek extends JPanel{ public static BufferedImage img = null; public Obrazek() { super(); try { img = ImageIO.read(new File("D:\\ja.jpg")); } catch (IOException e) {} } @Override public void paint(Graphics g) { g.drawImage(img, 0, 0, null); } } This is my load button private void przyciskWczytaj(java.awt.event.ActionEvent evt) { int odpowiedz = jFileChooser1.showOpenDialog(this); if (odpowiedz == jFileChooser1.APPROVE_OPTION) { File file = jFileChooser1.getSelectedFile(); try { BufferedImage im = ImageIO.read(new File(file.getAbsolutePath())); Obrazek.img = im; } catch (IOException ex) { System.out.println("Error"); } } } And now I want to create class where I will change that brightness. I have to use but I don't know how to use that thing: BufferedImage(256, 256, Bufferedmage.TYPE_INT_RGB) and to get each pixel of image I need to do something like: int rgb []=((DataBufferInt)img.getRaster().getDataBuffer()).getData(); And here I is next problem: How can I change the value of each r,g,b and show that new image on my panel

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  • Can we have a component-scoped bean in a JSF2 composite component?

    - by Pradyumna
    Hi, I was wondering how I could create "component-scoped" beans, or so-to-say, "local variables inside a composite component" that are private to the instance of the composite component, and live as long as that instance lives. Below are more details, explained with an example: Suppose there is a "calculator" component - something that allows users to type in a mathematical expression, and evaluates its value. Optionally, it also plots the associated function. I can make a composite component that has: a text box for accepting the math expression two buttons called "Evaluate", and "Plot" another nested component that plots the function It is evidently a self-contained piece of function; so that somebody who wants to use it may just say <math:expressionEvaluator /> But obviously, the implementation would need a java object - something that evaluates the expression, something that computes the plot points, etc. - and I imagine it can be a bean - scoped just for this instance of this component, not a view-scoped or request-scoped bean that is shared across all instances of the component. How do I create such a bean? Is that even possible with composite components?

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  • Multiple webroot folders with Jetty

    - by Lóránt Pintér
    I'm using Jetty (version 6.1.22) to service a Java web application. I would like to make Jetty look in two different folders for web resources. Take this layout: +- project1 | +- src | +- main | +- webapp | +- first.jsp | +- project2 +- src +- main +- webapp +- second.jsp I would like to make Jetty serve both URLs: http://localhost/web/first.jsp http://localhost/web/second.jsp I tried starting Jetty like this: Server server = new Server(); SocketConnector connector = new SocketConnector(); connector.setPort(80); server.setConnectors(new Connector[] { connector }); WebAppContext contextWeb1 = new WebAppContext(); contextWeb1.setContextPath("/web"); contextWeb1.setWar("project1/src/main/webapp"); server.addHandler(contextWeb1); WebAppContext contextWeb2 = new WebAppContext(); contextWeb2.setContextPath("/web"); contextWeb2.setWar("project2/src/main/webapp"); server.addHandler(contextWeb2); server.start(); But it only serves first.jsp, and it returns 404 for second.jsp. How can I get this to work?

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  • What is the correct stage to use for Google Guice in production in an application server?

    - by Yishai
    It seems like a strange question (the obvious answer would Production, duh), but if you read the java docs: /** * We want fast startup times at the expense of runtime performance and some up front error * checking. */ DEVELOPMENT, /** * We want to catch errors as early as possible and take performance hits up front. */ PRODUCTION Assuming a scenario where you have a stateless call to an application server, the initial receiving method (or there abouts) creates the injector new every call. If there all of the module bindings are not needed in a given call, then it would seem to have been better to use the Development stage (which is the default) and not take the performance hit upfront, because you may never take it at all, and here the distinction between "upfront" and "runtime performance" is kind of moot, as it is one call. Of course the downside of this would appear to be that you would lose the error checking, causing potential code paths to cause a problem by surprise. So the question boils down to are the assumptions in the above correct? Will you save performance on a large set of modules when the given lifetime of an injector is one call?

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  • Most efficient way of checking if Date object and Calendar object are in the same month

    - by Indigenuity
    I am working on a project that will run many thousands of comparisons between dates to see if they are in the same month, and I am wondering what the most efficient way of doing it would be. This isn't exactly what my code looks like, but here's the gist: List<Date> dates = getABunchOfDates(); Calendar month = Calendar.getInstance(); for(int i = 0; i < numMonths; i++) { for(Date date : dates) { if(sameMonth(month, date) .. doSomething } month.add(Calendar.MONTH, -1); } Creating a new Calendar object for every date seems like a pretty hefty overhead when this comparison will happen thousands of times, soI kind of want to cheat a bit and use the deprecated method Date.getMonth() and Date.getYear() public static boolean sameMonth(Calendar month, Date date) { return month.get(Calendar.YEAR) == date.getYear() && month.get(Calendar.MONTH) == date.getMonth(); } I'm pretty close to just using this method, since it seems to be the fastest, but is there a faster way? And is this a foolish way, since the Date methods are deprecated? Note: This project will always run with Java 7

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  • Hash Code for a group of three fields

    - by Gauranga
    I have three fields namely Number1 Number2 Time I am trying to write a function in java that returns a unique hash value (long needs to be the return type of hash) for the above fields. This hash would then be used to store database rows corresponding to the above mentioned fields in a HashSet. I am new to writing a hash code function, can someone please review what I have. Any help would be appreciated. public class HashCode { private long Number1; private long Number2; String Time; public HashCode(long Number1, long Number2, String Time){ this.Number1 = Number1; this.Number2 = Number2; this.Time = Time; } public long getHashCode() { long hash = 3; hash = 47 * hash + (long) (this.Number1 ^ (this.Number1 >>> 32)); hash = 47 * hash + (long) (this.Number2 ^ (this.Number2 >>> 32)); hash = 47 * hash + (this.Time != null ? this.Time.hashCode() : 0); return hash; } }

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  • How can I solve the Log Pile wooden puzzle with a computer program?

    - by craig1410
    Can anyone suggest how to solve the Log Pile wooden puzzle using a computer program? See here to visualise the puzzle: http://www.puzzlethis.co.uk/products/madcow/the_log_pile.htm The picture only shows some of the pieces. The full set of 10 pieces are configured as follows with 1 representing a peg, -1 representing a hole and 0 representing neither a peg nor a hole. -1,1,0,-1,0 1,0,1,0,0 1,-1,1,0,0 -1,-1,0,0,-1 -1,1,0,1,0 0,1,0,0,1 1,0,-1,0,-1 0,-1,0,1,0 0,0,-1,1,-1 1,0,-1,0,0 The pieces can be interlocked in two layers of 5 pieces each with the top layer at 90 degrees to the bottom layer as shown in the above link. I have already created a solution to this problem myself using Java but I feel that it was a clumsy solution and I am interested to see some more sophisticated solutions. Feel free to either suggest a general approach or to provide a working program in the language of your choice. My approach was to use the numeric notation above to create an array of "Logs". I then used a combination/permutation generator to try all possible arrangements of the Logs until a solution was found where all the intersections equated to zero (ie. Peg to Hole, Hole to Peg or Blank to Blank). I used some speed-ups to detect the first failed intersection for a given permutation and move on to the next permutation. I hope you find this as interesting as I have. Thanks, Craig.

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  • Connect.registerUsers - Need helping creating array for accounts param

    - by mw_javaguy
    I keep getting the following error when I try to invoke the Facebook REST API Call: Connect.registerUsers Error Code: 100 - param accounts must be an array JSON based response (from Facebook): {"error_code":100,"error_msg":"param accounts must be an array.","request_args": [{"key":"accounts","value":"{email_hash:5232156322_55ddgvc3db5ddcf218049dd564da2x06}"}, {"key":"api_key","value":"23b2c4c6a23445fbffssf8aab96a5e5"}, {"key":"format","value":"JSON"},{"key":"method","value":"Connect.registerUsers"},{"key":"sig","value":"3sd54153a31382fa6e72eecf3c57d7c9"},{"key":"v","value":"1.0"}],"message":"Unknown exception","code":0} I set up the Java code to invoke the REST end point using HttpClient like this: String API_KEY = "23b2c4c6a23445fbffssf8aab96a5e5"; String toConnectRegisterUsersSignature = "accounts=" + "{email_hash:" + emailHash + "}" + "api_key=" + API_KEY + "format=JSON" + "method=Connect.registerUsers" + "v=1.0" + "0c786155bd3cxe8228d924542da5gf2"; String connectRegisterUsersSignature = SimpleMd5.MD5(toConnectRegisterUsersSignature); NameValuePair[] connectRegisterUsersParameters = { new NameValuePair("accounts", "{email_hash:" + emailHash + "}"), new NameValuePair("api_key", API_KEY), new NameValuePair("format", "JSON"), new NameValuePair("method", "Connect.registerUsers"), new NameValuePair("sig", connectRegisterUsersSignature), new NameValuePair("v", "1.0") }; Tried the following combinations and I still get the same error! Signature: "accounts=" + "[email_hash=" + emailHash + "]" new NameValuePair("accounts", "[email_hash=" + emailHash + "]") Signature: "accounts=" + "email_hash[" + emailHash + "]" new NameValuePair("accounts", "email_hash[" + emailHash + "]") Signature: "accounts=" + "email_hash(" + emailHash + ")" new NameValuePair("accounts", "email_hash(" + emailHash + ")") Signature: "accounts=" + "[email_hash=" + emailHash + "]" new NameValuePair("accounts", "[email_hash=" + emailHash + "]") Signature: "accounts=" + "email_hash=" + emailHash new NameValuePair("accounts", "email_hash=" + emailHash) Signature: "accounts=" + "[{email_hash:" + emailHash + "}]" new NameValuePair("accounts", "[{email_hash:" + emailHash + "}]"), Does anyone know how to construct this array that the response is requesting? Happy programming and thank you for taking the time to read this.

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  • Will this web service accept both raw xml and an object?

    - by ChadNC
    We have a web service that provides auto insurance quotes and a company that provides an insurance agency management system would like to use the web service for thier client but they want to pass the web service raw xml instead of using the wsdl to create a port, the object the service expects and calling the web method. The web service has performed flawlessly by creating an object like so com.insurance.quotesvc.AgencyQuote service = new com.insurance.quotesvc.AgencyQuote(); com.insurance.quotesvc.QuotePortType port = service.getQuotePortType(); com.insurance.quotesvc.schemas.request.ACORD parameter = null; Then create initialize the request object with the other objects that make up the response. parameter = factory.createACORD(); parameter.setSignonRq(signOn); parameter.setInsurancesSvcRq(svcRq); And send the request to the web service. com.insurance.quotesvc.schemas.response.ACORD result = null; result = port.requestQuote(parameter); By doing that I am able to easily marshall the request and the result into an xml file and do with them as I wish. So if a client was to send the web service via an http post as raw xml inside of a soap envelope. Would the web service be able to handle the xml without any changes being made to the web service or would there need to be changes made to the web service in order for it to handle a request of that type? The web service is a JAX_WS and we currently have both Java and C# clients consuming the web service using the method described above but now there is another client who wants to send raw xml inside of a soap envelope instead of creating the objects. I feel pretty sure that they will be making the call to the web service using vb. I'm sure I'm missing something obvious but it is eluding me at the moment and any help is greatly appreciated.

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  • Quickest way to compare a bunch of array or list of values.

    - by zapping
    Can you please let me know on the quickest and efficient way to compare a large set of values. Its like there are a list of parent codes(string) and each code has a series of child values(string). The child lists have to be compared with each other and find out duplicates and count how many times they repeat. code1(code1_value1, code1_value2, code3_value3, ..., code1_valueN); code2(code2_value1, code1_value2, code2_value3, ..., code2_valueN); code3(code2_value1, code3_value2, code3_value3, ..., code3_valueN); . . . codeN(codeN_value1, codeN_value2, codeN_value3, ..., codeN_valueN); The lists are huge say like there are 100 parent codes and each has about 250 values in them. There will not be duplicates within a code list. Doing it in java and the solution i could figure out is. Store the values of first set of code in as codeMap.put(codeValue, duplicateCount). The count initialized to 0. Then compare the rest of the values with this. If its in the map then increment the count otherwise append it to the map. The downfall of this is to get the duplicates. Another iteration needs to be performed on a very large list. An alternative is to maintain another hashmap for duplicates like duplicateCodeMap.put(codeValue, duplicateCount) and change the initial hashmap to codeMap.put(codeValue, codeValue). Speed is what is requirement. Hope one of you can help me with it.

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  • How to call stored procedure by hibernate?

    - by user367097
    Hi I have an oracle stored procedure GET_VENDOR_STATUS_COUNT(DOCUMENT_ID IN NUMBER , NOT_INVITED OUT NUMBER,INVITE_WITHDRAWN OUT NUMBER,... rest all parameters are OUT parameters. In hbm file I have written - <sql-query name="getVendorStatus" callable="true"> <return-scalar column="NOT_INVITED" type="string"/> <return-scalar column="INVITE_WITHDRAWN" type="string"/> <return-scalar column="INVITED" type="string"/> <return-scalar column="DISQUALIFIED" type="string"/> <return-scalar column="RESPONSE_AWAITED" type="string"/> <return-scalar column="RESPONSE_IN_PROGRESS" type="string"/> <return-scalar column="RESPONSE_RECEIVED" type="string"/> { call GET_VENDOR_STATUS_COUNT(:DOCUMENT_ID , :NOT_INVITED ,:INVITE_WITHDRAWN ,:INVITED ,:DISQUALIFIED ,:RESPONSE_AWAITED ,:RESPONSE_IN_PROGRESS ,:RESPONSE_RECEIVED ) } </sql-query> In java I have written - session.getNamedQuery("getVendorStatus").setParameter("DOCUMENT_ID", "DOCUMENT_ID").setParameter("NOT_INVITED", "NOT_INVITED") ... continue till all the parametes . I am getting the sql exception 18:29:33,056 WARN [JDBCExceptionReporter] SQL Error: 1006, SQLState: 72000 18:29:33,056 ERROR [JDBCExceptionReporter] ORA-01006: bind variable does not exist Please let me know what is the exact process of calling a stored procedure from hibernate. I do not want to use JDBC callable statement.

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  • How to optimize shopping carts for minimal prices?

    - by tangens
    I have a list of items I want to buy. The items are offered by different shops and different prices. The shops have individual delivery costs. I'm looking for an optimal shopping strategy (and a java library supporting it) to purchase all of the items with a minimal total price. Example: Item1 is offered at Shop1 for $100, at Shop2 for $111. Item2 is offered at Shop1 for $90, at Shop2 for $85. Delivery cost of Shop1: $10 if total order < $150; $0 otherwise Delivery cost of Shop2: $5 if total order < $50; $0 otherwise If I buy Item1 and Item2 at Shop1 the total cost is $100 + $90 +$0 = $190. If I buy Item1 and Item2 at Shop2 the total cost is $111 + $85 +$0 = $196. If I buy Item1 at Shop1 and Item2 at Shop2 the total cost is $100 + $10 + $85 + $0 = 195. I get the minimal price if I order Item1 at Shop1 and Item2 at Shop2: $195 Question I need some hints which algorithms may help me to solve optimization problems of this kind for number of items about 100 and number of shops about 20. I already looked at apache-math and its optimization package, but I have no idea what algorithm to look for.

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  • how to convert minutes to days,hours,minutes

    - by tuxou
    hi how to convert minutes into days hours and minutes in java public String timeConvert(int time){ String t = ""; int h = 00; int m = 00; // h= (int) (time / 60); // m = (int) (time % 60); // if(h>=24) h=00; if((time>=0) && (time<=24*60)){ h= (int) (time / 60); m = (int) (time % 60); }else if((time>24*60) && (time<=24*60*2)){ h= (int) (time / (1440)); m = (int) (time % (1440)); }else if((time>24*60*2) && (time<=24*60*3)){ h= (int) (time / (2880)); m = (int) (time % (2880)); }else if((time>24*60*3) && (time<=24*60*4)){ h= (int) (time / (2880*2)); m = (int) (time % (2880*2)); }else if((time>24*60*4) && (time<=24*60*5)){ h= (int) (time / (2880*3)); m = (int) (time % (2880*3)); }else if((time>24*60*5) && (time<=24*60*6)){ h= (int) (time / (2880*4)); m = (int) (time % (2880*4)); }else if((time>24*60*6) && (time<=24*60*7)){ h= (int) (time / (2880*5)); m = (int) (time % (2880*5)); } t =h+":"+m ; return t; } I tried this but it dont work thanks

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  • How to create custom query for CollectionOfElements

    - by Shervin
    Hi. I have problems creating a custom query. This is what entities: @Entity public class ApplicationProcess { @CollectionOfElements private Set<Template> defaultTemplates; //more fields } And Template.java @Embeddable @EqualsAndHashCode(exclude={"file", "selected", "used"}) public class Template implements Comparable<Template> { @Setter private ApplicationProcess applicationProcess; @Setter private Boolean used = Boolean.valueOf(false); public Template() { } @Parent public ApplicationProcess getApplicationProcess() { return applicationProcess; } @Column(nullable = false) @NotNull public String getName() { return name; } @Column(nullable = true) public Boolean isUsed() { return used; } public int compareTo(Template o) { return getName().compareTo(o.getName()); } } I want to create a update statement. I have tried these two: int v = entityManager.createQuery("update ApplicationProcess_defaultTemplates t set t.used = true " + "WHERE t.applicationProcess.id=:apId").setParameter("apId", ap.getId()) .executeUpdate(); ApplicationProcess_defaultTemplates is not mapped [update ApplicationProcess_defaultTemplates t set t.used = true WHERE t.applicationProcess.id=:apId] And I have tried int v = entityManager.createQuery("update Template t set t.used = true " + "WHERE t.applicationProcess.id=:apId").setParameter("apId", ap.getId()) .executeUpdate(); With the same error: Template is not mapped [update Template t set t.used = true WHERE t.applicationProcess.id=:apId] Any ideas? UPDATE I fixed it by creating native query int v = entityManager.createNativeQuery("update ApplicationProcess_defaultTemplates t set t.used=true where t.ApplicationProcess_id=:apId").setParameter("apId", ap.getId()).executeUpdate();

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  • Under what circumstances will an entity be able to lazily load its relationships in JPA

    - by Mowgli
    Assuming a Java EE container is being used with JPA persistence and JTA transaction management where EJB and WAR packages are inside a EAR package. Say an entity with lazy-load relationships has just been returned from a JPQL search, such as the getBoats method below: @Stateless public class BoatFacade implements BoatFacadeRemote, BoatFacadeLocal { @PersistenceContext(unitName = "boats") private EntityManager em; @Override public List<Boat> getBoats(Collection<Integer> boatIDs) { if(boatIDs.isEmpty()) { return Collections.<Boat>emptyList(); } Query query = em.createNamedQuery("getAllBoats"); query.setParameter("boatID", boatIDs); List<Boat> boats = query.getResultList(); return boats; } } The entity: @Entity @NamedQuery( name="getAllBoats", query="Select b from Boat b where b.id in : boatID") public class Boat { @Id private long id; @OneToOne(fetch=FetchType.LAZY) private Gun mainGun; public Gun getMainGun() { return mainGun; } } Where will its lazy-load relationships be loadable (assuming the same stateless request): Same JAR: A method in the same EJB A method in another EJB A method in a POJO in the same EJB JAR Same EAR, but outside EJB JAR: A method in a web tier managed bean. A method in a web tier POJO. Different EAR: A method in a different EAR which receives the entity through RMI. What is it that restricts the scope, for example: the JPA transaction, persistence context or JTA transaction?

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  • In an Android application, should I have one content provider per table or only one for the entire a

    - by Andrew Dyer
    I have years of experience with Microsoft .NET development (primarily C#) and have been working to come up to speed on Android and Java. So far, I've built a small application with a couple screens and a working content provider. All of the examples I've seen for developing content providers typically work with a single table, so I got the impression that this was the convention. I built a couple more content providers for other tables and ran into the "Unknown URI" IllegalArgumentException when I tried to test them. The exception is being thrown by one of my content providers, but not the one I was intending to call. It appears that my application is using the first content provider in the AndroidManifest.xml file, which now has me wondering if I should only have a single content provider for the entire application. Are there any best practices and/or examples for working with multiple tables in an Android application? Should I have one content provider per table or only one for the entire application? If the former, how do I resolve URIs to the proper provider? If the latter, how do I keep my content provider code from being polluted with switch statements?

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  • Generate regular expression to match strings from the list A, but not from list B

    - by Vlad
    I have two lists of strings ListA and ListB. I need to generate a regular expression that will match all strings in ListA and will not match any string in ListB. The strings could contain any combination of characters, numbers and punctuation. If a string appears on ListA it is guaranteed that it will not be in the ListB. If a string is not in either of these two lists I don't care what the result of the matching should be. The lists typically contain thousands of strings, and strings are fairly similar to each other. I know the trivial answer to this question, which is just generate a regular expression of the form (Str1)|(Str2)|(Str3) where StrN is the string from ListA. But I am looking for a more efficient way to do this. Ideal solution would be some sort of tool that will take two lists and generate a Java regular expression for this. Update 1: By "efficient", I mean to generate expression that is shorter than trivial solution. The ideal algorithm would generate the shorted possible expression. Here are some examples. ListA = { C10 , C15, C195 } ListB = { Bob, Billy } The ideal expression would be /^C1.+$/ Another example, note the third element of ListB ListA = { C10 , C15, C195 } ListB = { Bob, Billy, C25 } The ideal expression is /^C[^2]{1}.+$/ The last example ListA = { A , D ,E , F , H } ListB = { B , C , G , I } The ideal expression is the same as trivial solution which is /^(A|D|E|F|H)$/ Also, I am not looking for the ideal solution, anything better than trivial would help. I was thinking along the lines of generating the list of trivial solutions, and then try to merge the common substrings while watching that we don't wander into ListB territory. *Update 2: I am not particularly worried about the time it takes to generate the RegEx, anything under 10 minutes on the modern machine is acceptable

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  • Code Golf: Counting XML elements in file on Android

    - by CSharperWithJava
    Take a simple XML file formatted like this: <Lists> <List> <Note/> ... <Note/> </List> <List> <Note/> ... <Note/> </List> </Lists> Each node has some attributes that actually hold the data of the file. I need a very quick way to count the number of each type of element, (List and Note). Lists is simply the root and doesn't matter. I can do this with a simple string search or something similar, but I need to make this as fast as possible. Design Parameters: Must be in java (Android application). Must AVOID allocating memory as much as possible. Must return the total number of Note elements and the number of List elements in the file, regardless of location in file. Number of Lists will typically be small (1-4), and number of notes can potentially be very large (upwards of 1000, typically 100) per file. I look forward to your suggestions.

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  • check if two subsets of integers are equal using equals method

    - by MAS
    I have this java method in class called IntArray. The class has methods to add integers to a set or remove integers from a set,check size of a set, and check if 2 sets are equal. the 2 sets are created using 2 different objects of type IntArray in main, lets say object A and B. equals method supposed to check if two sets of integers are equal. for example set A = {1,2,3} and B = {1,2,3,4}. The method still return true even though one set is a subset of the other set. What exactly I am doing wrong? Thanks. //part of the code in main IntArray A = new IntArray(); IntArray B = new IntArray(); if(A.equals(B)) System.out.println("A and B are equal"); //equals method in IntArray class public boolean equals(Object b) { if (b instanceof IntArray) { IntArray A = (IntArray) b; for (int i = 0; i < data.length; i++) if (countOccurrences(data[i]) != A.countOccurrences(data[i])) return false; return true; } else return false; }

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