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  • How can we compute the LAST page with JPA?

    - by Kevin
    I would like to implement pagination in my Servlet/EJB/JPA-Hibernate project, but I can't figure out how only one page from the query and know the number of pages I must display I use setFirstResult(int first) ; setMaxResults(int max) ; and that's working alright, but how can I know how many pages I will have in total? (Hibernate is my JPA provider, but I would prefer using only JPA if possible) UPDATE: COUNT() seems to be the better/easiest solution; but what can be the cost of SELECT COUNT(*) FROM ... in comparison with executeQuery("SELECT * FROM ...).getListResult().size() ?

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  • Better alternative for PipedReader/PipedWriter?

    - by Esko Luontola
    I need to have a buffered char stream, into which I write in one thread and from which I read in another thread. Right now I'm using PipedReader and PipedWriter for it, but those classes cause a performance problem: PipedReader does a wait(1000) when its internal buffer is empty, which causes my application to lag visibly. Would there be some library which does the same thing as PipedReader/PipedWriter, but with better performance? Or will I have to implement my own wheels?

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  • Reference and Value confusion

    - by rgamber
    Hi I read this question on Stack overflow, and tried to do an example. I had the below code: public static void main(String[] args){ int i = 5; Integer I = new Integer(5); increasePrimitive(i); increaseObject(I); System.out.println(i); //Prints 5 - correct System.out.println(I); //Still prints 5 System.out.println(increaseObject2(I)); //Still prints 5 } public static void increasePrimitive(int n){ n++; } public static void increaseObject(Integer n){ n++; } public static int increaseObject2(Integer n){ return n++; } Does the increaseObject print 5 because the value of reference is changing inside that function? Am I right? I am confused why the increasedObject2 prints 5 and not 6. Can anyone please explain?

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  • Netbeans configuration problem

    - by Yatendra Goel
    I am using Netbeans 6.8 The problem is that the projects explorer (that displays all the projects and their contents) displays each package as a node. For instance, if there is package hierarchy like this; com.mycompany.myproject.package1.package1.1 then it displays 5 nodes for the five packages which is very disturbing while development. Is there any way by which I can configure it(Netbeans) so that it groups all the subpackages of a package under one node and displays the subpackages only when I expand the package node?

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  • Do running times match with O(nlogn)?

    - by user472221
    Hi I have written a class(greedy strategy) that at first i used sort method which has O(nlogn) Collections.sort(array, new SortingObjectsWithProbabilityField()); and then i used the insert method of binary search tree which takes O(h) and h here is the tree height. for different n ,the running time will be : n,running time 17,515428 33,783340 65,540572 129,1285080 257,2052216 513,4299709 which I think is not correct because for increasing n , the running time should almost increase. This method will take the running time: Exponent = -1; for(int n = 2;n<1000;n+=Math.pow(2,exponent){ for (int j = 1; j <= 3; j++) { Random rand = new Random(); for (int i = 0; i < n; i++) { Element e = new Element(rand.nextInt(100) + 1, rand.nextInt(100) + 1, 0); for (int k = 0; k < i; k++) { if (e.getDigit() == randList.get(k).getDigit()) { e.setDigit(e.getDigit() + 1); } } randList.add(e); } double sum = 0.0; for (int i = 0; i < randList.size(); i++) { sum += randList.get(i).getProbability(); } for (Element i : randList) { i.setProbability(i.getProbability() / sum); } //Get time. long t2 = System.nanoTime(); GreedyVersion greedy = new GreedyVersion((ArrayList<Element>) randList); long t3 = System.nanoTime(); timeForGreedy = timeForGreedy + t3 - t2; } System.out.println(n + "," + "," + timeForGreedy/3 ); exponent++; } thanks

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  • Why doesn't list.get(0).equals(null) work?

    - by Jessy
    The first index is set to null (empty), but it doesn't print the right output, why? //set the first index as null and the rest as "High" String a []= {null,"High","High","High","High","High"}; //add array to arraylist ArrayList<Object> choice = new ArrayList<Object>(Arrays.asList(a)); for(int i=0; i<choice.size(); i++){ if(i==0){ if(choice.get(0).equals(null)) System.out.println("I am empty"); //it doesn't print this output } }

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  • Possible to skip track from an Android application?

    - by parse
    I'm planning on doing a application for Android 2.1 that changes song every minute (through what I hope exists in Android, "next") for the application using the audio device atm. So if I have Spotify running in background already, playing music, can I through my program change to the next track? Let me know if I was unclear about anything. Thanks in advance!

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  • which loop is faster?

    - by Mansuro
    I have this loop for (it= someCollection.iterator; it.hasNext(); ) { //some code here } I changed it to: for (it= someCollection.iterator;; ) { if (!it.hasNext()) break; //some code here } The second code ran a little bit faster in unit tests in junit on eclipse. Is the second loop faster? I'm asking because the times given by Junit are not too exact, but they give an approximate value

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  • What values do the walkback array in the SocketException contain?

    - by akhilss
    Recently I have debugging into a problem where a connection to a database server from the application server get reset. I am pretty sure there is no reset being called from either end. But while I was debugging into the problem, while inspecting the SocketException, I found the walkback variable. arg0 SocketException (id=11532) cause SocketException (id=11532) detailMessage "Connection reset" stackTrace null walkback long[50] (id=11618) What do the values in this variable represent?

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  • Is map/collection order stable between calls?

    - by John
    If I have a hash map and iterate over the objects repeatedly, is it correct that I'm not guaranteed the same order for every call? For example, could the following print two lines that differ from each other: Map<String,Integer> map = new HashMap<String,Integer>() {{ put("a", 1); put("b", 2); put("c", 3); }}; System.out.println(map); System.out.println(map); And is this the case for sets and collections in general? If so, what's the best way in case you have to iterate twice over the same collection in the same order (regardless of what order that is)? I guess converting to a list.

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  • Beside SVN, how do you manage your development vs test vs production source code?

    - by medopal
    I'm working on a very large project with three phases of source code. Development source code: changes rapidly every second, and checked by our QA Test environment code: released to clients' QA department (released every 2-3 weeks) Production environment: after confirmed ok by client QA its released to prod. (every few months) The system (governmental web app) is very large to track changes,bugs and hot fixes, sometimes the Testers could ask for a change, some other times the Production could ask for a hot fix or small update. The problem is, when the Test or Production request changes, the development code is already changed a lot, and they always warn us they want only that small fix, do not upload anything new with it. The question, how should i manage the code for the 3 phases, and get back to Test or Production code any tie and fix that small one thing (reflecting the change to the current Development as well)? Note: making a branch each time is too much, and i don't want the developers to be lost between updating the mainstream, the branch and the Test code!

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  • what is the difference between MVC1 and MVC2

    - by Alaa
    I am using MVC design pattern in jsp-servlet web application, and want to what is the exact difference between MVC1 and MVC2 , can someone help? EDIT newly I hear that there is 2 versions of using MVC in servlet programming, I hear that in MVC1 there is kind of coupling between controller and view , but in MVC2 they overtake it, if someone know whether this is right or wrong I'll be very thankful.

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  • Noob question about hibernate criteria

    - by Dimitri
    Hello, I have a class called User which has 2 properties : login/password. I am trying to authenticate a user in my application using hibernate criteria but my request doesn't work. [EDIT] The returned value is NULL. I have two users in my database for testing. Here is my code : @Override public User authenticate(String login, String password) throws NullPointerException { Session session = this.getSession(); User user = (User) session .createCriteria(User.class) .add( Restrictions.and( Property.forName("login").eq(login), Property.forName("password").eq(password) )).uniqueResult(); if (user == null){ throw new NullPointerException("User not found"); } return user; } Can someone tells me what is wrong with my code? Happy new Year 2011 !!

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  • Renaming the argument name in JAX-WS

    - by user182944
    I created a web service using JAX-WS in RSA 7.5 and Websphere 7 using bottom-up approach. When I open the WSDL in SOAP UI, then the arguments section is appearing like this: <!--Optional--> <arg0> <empID>?</empId> </arg0> <!--Optional--> <arg1> <empName>?</empName> </arg1> <!--Optional--> <arg2> <empAddress>?</empAddress> </arg2> <!--Optional--> <arg3> <empCountry>?</empCountry> </arg3> The service method takes the above 4 elements as the parameters to return the employee details. 1) I want to rename this arg0, arg1, and so on with some valid names. 2) I want to remove the <!--optional--> present above the arg tags. (For removing the <!--optional--> from elements name, I used @XMLElement(required=true)). But I am not sure where exactly to use this annotation in this case :( Please help. Regards,

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  • Variable from block is put into a calculation but throws off wrong reading

    - by user2926620
    I am having troubles with trying to retrieve a double variable that is already established outside the block and called inside but I want to return the value of the same variable so that I can apply it to a calculation. the variable that I want returned is: double quarter = 0; but when I plug it into quarter in my first else/if statement, it plugs in 0 and not the value in my switch block. What can I do to retrieve the value? double quarter = 0; //Date entry will be calculated by how much KW user enters switch (input) { case "2/15/13": quarter = kwUsed * 0.10; break; case "4/15/13": quarter = kwUsed * 0.12; break; case "8/15/13": quarter = kwUsed * 0.15; break; case "11/15/13": quarter = kwUsed * 0.15; break; default: System.out.println("Invalid date"); } //Declaring variables for calculations double base = 0; double over = 0; double excess = 0; double math1 = 0; double math2 = 0; //KW Calculations if (kwUsed <= 350) { base = quarter; }else if (kwUsed <= 500) { math1 = ((kwUsed - 350) * quarter); base = ((kwUsed * quarter) - math1); over = ((math1 * 0.1) + math1); }else if (kwUsed > 500) { math2 = ((kwUsed - 350) * 0.1); base = ((kwUsed * 0.1) - math2); math2 = ((kwUsed -350) - 50); over = ((math2 * 0.1) + (15 * 0.1)); double math3 =((kwUsed - 500) * 0.1); excess = ((math3 * 0.25) + math3); } Edited to clarify question.

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  • is this class thread safe?

    - by flash
    consider this class,with no instance variables and only methods which are non-synchronous can we infer from this info that this class in Thread-safe? public class test{ public void test1{ // do something } public void test2{ // do something } public void test3{ // do something } }

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  • IS ResultSet thread safe

    - by javatraniee
    Is ResultSet Thread safe? My question arises because in this i have used a different statement for each query i have delsared a ResultSet as an local variable but it gives me a error of Operation not allowed after ResultSet is closed. But my statements are working as i'm using the statements in insert and delete query.I have commented the ResultSet part and have not got the error !! The source code of my program can be referd to , in my earlier Question .

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