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  • Any big difference between using contains or loop through a list?

    - by Nazgulled
    Hi, Performance wise, is there really a big difference between using: ArrayList.contains(o) vs foreach|iterator LinkedList.contains(o) vs foreach|iterator HashMap.(containsKey|containsValue) vs foreach|iterator TreeMap.(containsKey|containsValue) vs foreach|iterator Of course, for the foreach|iterator loops, I'll have to explicitly compare the methods and return true or false accordingly. The object I'm comparing is an object where equals() and hashcode() are both properly overridden.

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  • Howto check if a object is connected to another in hibernate

    - by codevourer
    Imagine two domain object classes, A and B. A has a bidirectional one-to-many relationship to B. A is related to thousands of B. The relations must be unique, it's not possible to have a duplicate. To check if an instance of B is already connected to a given instance of A, we could perform an easy INNER JOIN but this will only ensure the already persisted relations. What about the current transient relations? class A { @OneToMany private List<B> listOfB; } If we access the listOfB and perform a check of contains() this will fetch all the connected instances of B lazy from the datasource. I only want to validate them by their primary-key. Is there an easy solution where I can do things like "Does this instance of A is connected with this instance of B?" Without loading all these data into memory and perform a based on collections?

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  • req.getParameter returns values wrong character encoding

    - by coder247
    I'm trying to get values from a JSP using getParameter which includes ü,é,à etc. But get wrong values in servlet. I've checked the content type with firebug and found that Content-Type text/html;charset=UTF-8 checked the POST section with firebug and found the correct value there, when I try to access it in servlet it is wrong. Gives ö instead of ö req.getCharacterEncoding(); returns null. Tried with setting req.setCharacterEncoding("UTF-8"); at the beginning of servlet but didn't help.

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  • Find top N elements in a Multiset from Google Collections?

    - by dfrankow
    A Google Collections Multiset is a set of elements each of which has a count (i.e. may be present multiple times). I can't tell you how many times I want to do the following Make a histogram (exactly Multiset) Get the top N values from the histogram Examples: top 10 URLs, top 10 tags, ... What is the canonical way to do #2 given a Multiset? Here is a blog post about it, but that code is not quite what I want. First, it returns everything, not just top N. Second, it copies (is it possible to avoid a copy?). Third, I usually want a deterministic sort, i.e. tiebreak if counts are equal.

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  • Eclipse: Should I create a workspace for each project ?

    - by Zombies
    I am simply wondering whether it is best to put all of my Eclipse projects into one workspace, or do a 1 workspace per 1 project. I am just a solo developer, for hobby more or less, but the apps I create do actually have production versions that are running on rather frequent cron jobs, so its almost like an amateur production environment. The only problems I have noticed so far is for exporting JARs, I have the potential to include source files from other projects which seems like it could get messy (maybe?).

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  • Creating a shared HSQLDB database

    - by Robert Munteanu
    In-process HSQLDB database are not expected to be opened by others, even for file-based storage. The documentation hints that this is possible: Server Modes, Advanced Topics, but I've not yet found a URL for how to activate this behaviour. Did anyone do this so they can share how to?

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  • How to implement a ilike Facebook system without user authentication and still prevent users from cheating ?

    - by fabien7474
    Hi, I am trying to implement something done in almost any website out there : a 'ilike' button (like Facebook) that does not require user authetication to be used for any article of my website written in Grails. I don't want to use any external solution, so I need to implement it myself (or use a grails plugin). So my question is : What does it take to implement this 'ilike' button and prevent users from cheating? For instance, do I need to store local cookies (I suppose yes)? Do I need to check the session ID and IP of the HTTP request? Any well-known implementation are welcomed. Thank you very much for your help.

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  • When should EntityManagerFactory instance be created/opened ?

    - by masato-san
    Ok, I read bunch of articles/examples how to write Entity Manager Factory in singleton. One of them easiest for me to understand a bit: http://javanotepad.blogspot.com/2007/05/jpa-entitymanagerfactory-in-web.html I learned that EntityManagerFactory (EMF) should only be created once preferably in application scope. And also make sure to close the EMF once it's used (?) So I wrote EMF helper class for business methods to use: public class EmProvider { private static final String DB_PU = "KogaAlphaPU"; public static final boolean DEBUG = true; private static final EmProvider singleton = new EmProvider(); private EntityManagerFactory emf; private EmProvider() {} public static EmProvider getInstance() { return singleton; } public EntityManagerFactory getEntityManagerFactory() { if(emf == null) { emf = Persistence.createEntityManagerFactory(DB_PU); } if(DEBUG) { System.out.println("factory created on: " + new Date()); } return emf; } public void closeEmf() { if(emf.isOpen() || emf != null) { emf.close(); } emf = null; if(DEBUG) { System.out.println("EMF closed at: " + new Date()); } } }//end class And my method using EmProvider: public String foo() { EntityManager em = null; List<Object[]> out = null; try { em = EmProvider.getInstance().getEntityManagerFactory().createEntityManager(); Query query = em.createNativeQuery(JPQL_JOIN); //just some random query out = query.getResultList(); } catch(Exception e) { //handle error.... } finally { if(em != null) { em.close(); //make sure to close EntityManager } } I made sure to close EntityManager (em) within method level as suggested. But when should EntityManagerFactory be closed then? And why EMF has to be singleton so bad??? I read about concurrency issues but as I am not experienced multi-thread-grammer, I can't really be clear on this idea.

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  • How to organize RMI Client-Server eBanking architecture

    - by xenom
    I am developing a secured eBanking service in RMI with a GUI both for Server and Client. The Server must be able to log every operations (new User, deleted User, Withdrawal, Lodgement...) The Client will do these operations. As everything is secured, the Client must at first, create an account with a name and a password in the GUI. After that, the GUI adds the User in the Bank UserList(arrayList) as a new Customer and the User can do several operations. It seems straightforward at first but I think my conception is not correct. Is it correct to send the whole Bank by RMI ? Because at first I thought Bank would be the server but I cannot find another way to do that. Currently, the Client GUI asks for a login and a password, and receives the Bank by RMI. A User is characterized by a name and a hash of the password. private String name; private byte[] passwordDigest; In fact the GUI is doing every security checking and I don't know if it's relevant. When you type login//password, it will search the login in the Bank and compare the hash of the password. In fact I have the impression that the Client knows too much information because when you have the Bank you have everything.. Does it seem correct or do I need to change my implementation ?

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  • How does quartz track the time

    - by Nrj
    How does quartz track the time ? Is it a continuous timer running in background or does it somehow uses the OS scheduler or is it something else ? Which class actually holds this feature ? Thanks.

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  • Which technology should I choose for 3d globe web application

    - by uther-lightbringer
    Hello, i would like to ask you for an advice. I'm currently developing application in Spring consisting of Spring CRUD application as backend, SpringMVC application as tool for management and third part is where my problem lies as I need have application that renders 3d globe which is fed by data from backend from a data set selected by user (user may switch those at will). It has to be web application (though I would prefer not to implement this in flash/flex), composed of two main parts - main part is classic web GUI where user makes his choices and second part is 3d globe which renders the globe with selected set of data visualised. My question is, what do you think is the best option to implement this? Would be SpringMVC framework usable for this kind of application? I will be gratefull for any leads or directions, thank you.

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  • How to use Boolean variable in c:if

    - by Patriks
    I am using this code in jsf <c:if test="#{sV.done.booleanValue()}"> <option value="#{sV.id}" selected="selected">#{sV.text}</option> </c:if> <c:if test="#{not sV.done.booleanValue()}"> <option value="#{sV.id}">#{sV.text}</option> </c:if> sv is my class containing data (pojo), done is an Boolean variable, I want to display option tag with selected attribute if sV.done is true. But I couldn't make it. Don't know where I am wrong. Otherwise there can be something worong with c? because c:forEach was not working before some time in my case in same page. it can be the reason? Where I am wrong?

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  • How to call SOAP web service in Android

    - by BobbyShaftoe
    I am having a lot of trouble finding good information on how to call a standard SOAP/WSDL web service with Android. All I've been able to find are either very convoluted documents and references to "kSoap2" and then some bit about parsing it all manually with SAX. OK, that's fine, but it's 2008 so I figured there should be some good library for calling standard web services. The web service is just basically one created in NetBeans. I would like to have IDE support for generating the plumbing classes. I just need the easiest/most-elegant way to contact a WSDL based web service from an Android based phone.

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  • Android pattern for activity "flows"

    - by Otto
    I'm developing an android app that has a bunch of screens (activities) that are supposed to have "continue" and "back" buttons at the top. Can you tell me the right pattern for implementing this? I've seen some iPhone apps that have this but Android apps usually don't (I think partly because the back button is part of the phone). I found a post online about an Activity class that has "sub activities" which kind of seems like what I want to do, but I'm wondering if there's a simpler solution or pattern for creating flows like this (in which several activities are linked with continue/back buttons).

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  • How to use JAXB APIs to generate classes from xsd?

    - by Simran
    I need to generate bean classes from .xsd without using xjc command or ant. i have found the implementation in Apache Axis2 but i am unable to generate the artifacts. i have written the following code but i get NullPointerException : SchemaCompiler sc = XJC.createSchemaCompiler(); URL url = new URL("file://E:\\JAXB\\books.xsd"); sc.parseSchema(new InputSource(url.toExternalForm())); S2JJAXBModel model = sc.bind(); JCodeModel cm = model.generateCode(null, null); cm.build(new FileCodeWriter(new File("E:\\JAXBTest"))); Can anyone help me / provide some links???

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  • download file exception handling

    - by klaus-vlad
    Hi, In my application I download several critical files from a server, and I want to write some code that handles the case where the a file download didn't complete for a reason or other ,to retry downloading it at next startup. The function that downloads a file at a time however throws only MalformedURLException and IOException , but if these exceptions are thrown that means that the download didn't even begin. How should I arrange things so I can treat the case where a download failed , even if it began ? download(String file) throws MalformedURLException ,IOException { }

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  • "Zoom" text to be as big as possible within constraints/box

    - by stolsvik
    First problem: You have 400 pixels width to go on, and need to fit some text within that constraint as large as possible (thus, the text shall use that amount of space). Throw in a new constraint: If the text is just "A", then it shall not zoom this above 100 pixels (or some specific font size). Then, a final situation: Linebreaks. Fit some text in the largest possible way within e.g. 400 x 150 pixels. An obvious way is to simply start with point 1, and then increase until you can't fit it anymore. This would work for all three problems, but would be very crude. The fitting of a single line within bounds could be done by writing it with some fixed point size, check the resulting pixel bounds of the text, and then simply scale it with a transform (the text scales properly too then, check out TransformUI). Any ideas of other ways to attack this would be greatly appreciated!

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  • Loop and ListView

    - by monomi
    I find a match with Regexp. How to correctly organize a loop, if more than one match and write it in the ListView? listAlbums = (ListView)findViewById(R.id.listAlbums); ... Pattern patternNameToId = Pattern.compile(kRegexp); String nameTo = "" Matcher matcherName = patternNameToId.matcher(response); if (matcherName.find()) { nameTo = matcherTopicTitle.group(2); albumsList = new ArrayList<String>(); albumsList.add(nameTo); ArrayAdapter<String> adapter = new ArrayAdapter<String>(context, android.R.layout.simple_list_item_1, albumsList); listAlbums.setAdapter(adapter); } else Toast.makeText(context, "?? ???????", Toast.LENGTH_LONG).show();

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  • Why in the following code the output is different when I compile or run it more than once

    - by Sanjeev
    class Name implements Runnable { public void run() { for (int x = 1; x <= 3; x++) { System.out.println("Run by " + Thread.currentThread().getName() + ", x is " + x); } } } public class Threadtest { public static void main(String [] args) { // Make one Runnable Name nr = new Name(); Thread one = new Thread(nr); Thread two = new Thread(nr); Thread three = new Thread(nr); one.setName("A"); two.setName("B"); three.setName("C"); one.start(); two.start(); three.start(); } } The answer is different while compiling and running more then one time I don't know why? any idea.

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  • I can't set main Class variable in onCreate Method

    - by natrollus
    Main class has two variables that want to reach another class: public class MyClassA extends Activity { int i = 1; Button b1; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); this.i = 31; this.b1 = (Button) findViewById(R.id.btn1); ~~ } } Second class want to call variables in mainClass object: public class MyclassB implements OnClickListener{ MyClassA mainClass = new MyClassA(); Button btn = mainClass.b1; int n = mainClass.i; public void OnClick(View arg0){ Log.v("btn:",btn); Log.v("int:",n); } //btn returns null; //int returns 1; But onCreate method not set variables.. Why not set main class variables like this.i=31 ?

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  • Write to text file using ArrayList

    - by Ugochukwutubelum Chiemenam
    The program is basically about reading from a text file, storing the current data into an ArrayList, then writing data (from user input) into the same text file. Kindly let me know where I am going wrong in this sub-part? The data inside the text file is as follows: abc t1 1900 xyz t2 1700 The compiler is showing an error at the line output.format("%s%s%s%n", public class justTesting { private Scanner input; private Formatter output; private ArrayList<Student> tk = new ArrayList<Student>(); public static void main(String[] args) { justTesting app = new justTesting(); app.create(); app.writeToFile(); } public void create() { Text entry = new Text(); Scanner input = new Scanner(System.in); System.out.printf("%s\n", "Please enter your name, ID, and year: "); while (input.hasNext()) { try { entry.setName(input.next()); entry.setTelNumber(input.next()); entry.setDOB(input.next()); for (int i = 0; i < tk.size(); i++) { output.format("%s%s%s%n", tk.get(i).getName(), tk.get(i) .getTelNumber(), tk.get(i).getDOB()); } } catch (FormatterClosedException fce) { System.err.println("Error writing to file."); return; } catch (NoSuchElementException nsee) { System.err.println("Invalid input. Try again: "); input.nextLine(); } System.out.printf("%s\n", "Please enter your name, ID, and year: "); } } public void writeToFile() { try { output = new Formatter("testing.txt"); } catch (SecurityException se) { System.err .println("You do not have write access permission to this file."); System.exit(1); } catch (FileNotFoundException fnfe) { System.err.println("Error opening or creating file."); System.exit(1); } } }

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