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  • Hibernate Queries

    - by Schildmeijer
    Using Named Queries (located in your hibernate mapping xml file) is a nice way to separate your queries from your buisness logic. But what are the alternatives if your are using Hibernate Annotations for mapping?

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  • Interview question : What is the fastest way to generate prime number recursively ?

    - by hilal
    Generation of prime number is simple but what is the fastest way to find it and generate( prime numbers) it recursively ? Here is my solution. However, it is not the best way. I think it is O(N*sqrt(N)). Please correct me, if I am wrong. public static boolean isPrime(int n) { if (n < 2) { return false; } else if (n % 2 == 0 & n != 2) { return false; } else { return isPrime(n, (int) Math.sqrt(n)); } } private static boolean isPrime(int n, int i) { if (i < 2) { return true; } else if (n % i == 0) { return false; } else { return isPrime(n, --i); } } public static void generatePrimes(int n){ if(n < 2) { return ; } else if(isPrime(n)) { System.out.println(n); } generatePrimes(--n); } public static void main(String[] args) { generatePrimes(200); }

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  • Should try...catch go inside or outside a loop?

    - by mmyers
    I have a loop that looks something like this: for(int i = 0; i < max; i++) { String myString = ...; float myNum = Float.parseFloat(myString); myFloats[i] = myNum; } This is the main content of a method whose sole purpose is to return the array of floats. I want this method to return null if there is an error, so I put the loop inside a try...catch block, like this: try { for(int i = 0; i < max; i++) { String myString = ...; float myNum = Float.parseFloat(myString); myFloats[i] = myNum; } } catch (NumberFormatException ex) { return null; } But then I also thought of putting the try...catch block inside the loop, like this: for(int i = 0; i < max; i++) { String myString = ...; try { float myNum = Float.parseFloat(myString); } catch (NumberFormatException ex) { return null; } myFloats[i] = myNum; } So my question is: is there any reason, performance or otherwise, to prefer one over the other? EDIT: The consensus seems to be that it is cleaner to put the loop inside the try/catch, possibly inside its own method. However, there is still debate on which is faster. Can someone test this and come back with a unified answer? (EDIT: did it myself, but voted up Jeffrey and Ray's answers)

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  • Help choosing the right data structure

    - by devoured elysium
    I need a data structure with the following requirements: Needs to be able to get elements by index (like a List). I will always just add / remove elements from the end of the structure. I am inclined to use an ArrayList. In this situation, it seems to be O(1) both to read elements (they always are?), remove elements (I only need to remove them at the end of the list) and to add(I only add to the end of the list). There is only the problem that time to time the ArrayList will have a performance penalty when it's completly full and I need to add more elements to it. Is there any other better idea? I don't think of a data structure that'd beat the ArrayList here. Thanks

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  • Passing bundle to activity set as singletask

    - by Falmarri
    So I have a MapActivity that runs an asynchtask that occasionally updates what exactly it's displaying on the map (via a string). I originally pass this string in from the intent when the activity is first created. And then if you click on one of the drawables on the map, it opens a new activity, which can then create a new mapview (same class) with a different string setting. The problem I have is that I only want one instance of the mapview to be running at once. Thus I set android:launchmode="singletask" in the manifest. This works in that it brings the mapactivity to the front, but is there any way to send it a new intent bundle to get a new setting for the string it needs? I tried regetting the extras from the bundle, but it seems to retain the old bundle, not the new intent that was passed to it. I'm not sure I want to do startActivityForResult because the 2nd activity may or may not want to update the original activity. I hope that made sense. I can post code if necessary, but I think that should explain my situation.

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  • Project Euler #119 Make Faster

    - by gangqinlaohu
    Trying to solve Project Euler problem 119: The number 512 is interesting because it is equal to the sum of its digits raised to some power: 5 + 1 + 2 = 8, and 8^3 = 512. Another example of a number with this property is 614656 = 28^4. We shall define an to be the nth term of this sequence and insist that a number must contain at least two digits to have a sum. You are given that a2 = 512 and a10 = 614656. Find a30. Question: Is there a more efficient way to find the answer than just checking every number until a30 is found? My Code int currentNum = 0; long value = 0; for (long a = 11; currentNum != 30; a++){ //maybe a++ is inefficient int test = Util.sumDigits(a); if (isPower(a, test)) { currentNum++; value = a; System.out.println(value + ":" + currentNum); } } System.out.println(value); isPower checks if a is a power of test. Util.sumDigits: public static int sumDigits(long n){ int sum = 0; String s = "" + n; while (!s.equals("")){ sum += Integer.parseInt("" + s.charAt(0)); s = s.substring(1); } return sum; } program has been running for about 30 minutes (might be overflow on the long). Output (so far): 81:1 512:2 2401:3 4913:4 5832:5 17576:6 19683:7 234256:8 390625:9 614656:10 1679616:11 17210368:12 34012224:13 52521875:14 60466176:15 205962976:16 612220032:17

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  • How to format dates in Jahia 6 CMS?

    - by dpb
    I am helping a friend of mine put up a site for his business. I’ve read different posts and sites trying to find the ideal CMS tool, but people have different views of what is the best, so I finally just picked one of them at random. So I went for an evaluation of Jahia 6.0-CE. As you’ve probably guessed by now, I don’t have so much experience with CMS tools. I just want to setup the CMS, write the templates for the site and let my friend manage the content from there on. So I extracted the sources from SVN and went for a test drive. I managed to create some simple templates to get a hang of things but now I have an issue with a date format. In my definitions.cnd I declared the field like so: date myDateField (datetimepicker[format='dd.MM.yyyy']) This is formatted in the page and the selector also presents this in the dd.MM.yyyy format when inserting the content. But how about sites in other countries, countries that represent the date as MM.dd.yyyy for example? If I specify the format in the CND, hard coded, how can I change this later on so that it adapts based on the browser’s language? Do I extract the content from the repository and format it by hand in the JSP template based on a Locale, or is there a better way? Thank you.

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  • Prevent browser form submission when Wicket AjaxFormValidatingBehaviour validation fails

    - by Brian Laframboise
    I have a Page with a Wizard component. The user can navigate the panels of the wizard by using the next and previous buttons which I have performing full (non-ajax) form submissions so that the app is back-button friendly. When the next button is clicked, I would like to attempt ajax form validation (if javascript is enabled). I tried doing: nextButton.add( new AjaxFormValidatingBehavior( form, "onsubmit") ); to add such validation. The behaviour works - however, when validation errors occur the browser still submits the entire form. What is the Wicket way to prevent the browser from submitting the form in this case?

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  • Velocity templates seem to fail with UTF-8

    - by steve
    Hi, i have been trying to use a velocity Template with the following content: Sübjäct $item everything works fine except the translation of the tow unicode characters. The result string printed on the commandline looks like: Sübjäct foo I searched the velocity website and the web an this issue, and came uo with differnt font encoding options, which i added to my code. But those won't help. This is the actuall code: velocity.setProperty("file.resource.loader.path", absPath); velocity.setProperty("input.encoding", "UTF-8"); velocity.setProperty("output.encoding", "UTF-8"); Template t = velocity.getTemplate("subject.vm"); t.setEncoding("UTF-8"); StringWriter sw = new StringWriter(); t.merge(null, sw); System.out.println(sw.getBuffer()); Can anyone give me some hints, how to fix this issue?

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  • null pointer exception on list.add

    - by Eric
    I've been working on this one error for a few hours so I thought I'd pick the brains of some pros. I am getting a null pointer exception at the modelData.add(i, es) method. I know from debugging that es isn't null. I'm really confused, thanks. public class EventTableModel extends AbstractTableModel { //private int rowCount = 0; protected List<EventSeat> modelData; private static final int COLUMN_COUNT = 3; private Event e; Event j = GUIpos.m; int i = 1; public EventTableModel(Event e) { this.e = e; try { System.out.println(modelData); for (EventSeat es : e.getEventSeats()) { modelData.add(i, es); i++; } } catch (DataException ex) { Logger.getLogger(EventTableModel.class.getName()).log(Level.SEVERE, null, ex); } }

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  • Counting the number of occurrences of characters in an array

    - by Anthony Pittelli
    This is what I have but it is not working, this is confusing for me. If you scroll down I commented on someones post the exact problem I am having and what I am trying to do. I was thinking maybe the problem is my code to generate the random characters: public void add (char fromChar, char toChar){ Random r = new Random(); //creates a random object int randInt; for (int i=0; i<charArray.length; i++){ randInt = r.nextInt((toChar-fromChar) +1); charArray[i] = (char) randInt; //casts these integers as characters } }//end add public int[] countLetters() { int[] count = new int[26]; char current; for (int b = 0; b <= 26; b++) { for (int i = 97; i <= 123; i++) { char a = (char) i; for (int ch = 0; ch < charArray.length; ch++) { current = charArray[ch]; if (current == a) { count[b]++; } } } } return count; }

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  • executorservice to read data from database in chuncks and run process on them

    - by TazMan
    I'm trying to write a process that would read data from a database and upload it onto a cloud datastore. How can I decide the partition strategy of the data? I want to query the table in chunks and process each chunk in 10 threads. Each thread basically will send the data to an individual node on a 10 node cluster on the cloud.. Where in the below multi threading code will the dataquery to extract and send 10 concurrent requests for uploading data to cloud would be? public class Caller { public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(10); for (int i = 0; i < 10; i++) { Runnable worker = new DomainCDCProcessor(i); executor.execute(worker); } executor.shutdown(); while (!executor.isTerminated()) { } System.out.println("Finished all threads"); } }

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  • Question regarding the method local innerclasses accesing the local variables of the method

    - by flash
    Hi I was going through the SCJP book about the innerclasses, and found this statement, it goes something like this. "A method local class can only refer to the local variables which are marked final" and in the explanation the reason specified is about the scope and lifetime of the local class object and the local variables on the heap, But I am unable to understand that.am I missing anything here about 'final'??

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  • Mysql maven jpa skeleton

    - by coubeatczech
    Hi, is there a skeleton for a project using mysql, some eclipse/top link with RESOURCE_LOCAL as connection type? Preferably using maven. I'm searching for it for hours and can't get running even the sipmlest exaple. So if you had it ready and running, please, post :-). Even something as simple as these two classes only. @Entity public class Message implements Serializable{ public Message() {} public Message(String s){ this.s = s; } @Id String s; public String getS(){ return s; } } public class App { static private EntityManagerFactory emf; static private EntityManager em; public static void main( String[] args ) { emf = Persistence.createEntityManagerFactory("persistence"); em = emf.createEntityManager(); Message m = new Message("abc"); em.persist(m); } }

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  • How to avoid the linebreak inside a word (Static Layout

    - by Addev
    I'm trying to make a text as big as I can making it fit a Rect. basically I use a StaticLayout for pre-calculate the text size and make it fit the Rect's height: // Since the width is fixed for the StaticLayout it should only fit the height while (currentHeight>Rect.getHeight()){ size-=2; } textPaint.setTextSize(size); The problem is that if the Rect is very high, the exit condition is reached but breaking the words (see the capture). Is there a way for avoid this? Goal: Actual: Current code: textSize=MAX_TEXT_SIZE do { if (textSize < mMinTextSize) { Log.i(TAG, "Min reached"); textSize = mMinTextSize; textPaint.setTextSize(textSize); fits = true; } else { textPaint.setTextSize(textSize); StaticLayout layout = new StaticLayout(text, textPaint, targetWidth, Alignment.ALIGN_NORMAL, 1.0, 0, true); layout.draw(canvas); float heightRatio= (float) layout.getHeight() / (float) targetHeight; boolean fitsHeight = heightRatio<= 1f; if (fitsHeight) { fits = true; } else { textSize -= 2; } } Log.i(TAG, "textSize=" + textSize + " fits=" + fits); } while (!fits); thanks

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  • Iterative Reduction to Null Matrix

    - by user1459032
    Here's the problem: I'm given a matrix like Input: 1 1 1 1 1 1 1 1 1 At each step, I need to find a "second" matrix of 1's and 0's with no two 1's on the same row or column. Then, I'll subtract the second matrix from the original matrix. I will repeat the process until I get a matrix with all 0's. Furthermore, I need to take the least possible number of steps. I need to print all the "second" matrices in O(n) time. In the above example I can get to the null matrix in 3 steps by subtracting these three matrices in order: Expected output: 1 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 1 0 0 1 0 0 0 1 1 0 0 I have coded an attempt, in which I am finding the first maximum value and creating the second matrices based on the index of that value. But for the above input I am getting 4 output matrices, which is wrong: My output: 1 0 0 0 1 0 0 0 1 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 1 0 My solution works for most of the test cases but fails for the one given above. Can someone give me some pointers on how to proceed, or find an algorithm that guarantees optimality? Test case that works: Input: 0 2 1 0 0 0 3 0 0 Output 0 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0

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  • Any techniques to interrupt, kill, or otherwise unwind (releasing synchronization locks) a single de

    - by gojomo
    I have a long-running process where, due to a bug, a trivial/expendable thread is deadlocked with a thread which I would like to continue, so that it can perform some final reporting that would be hard to reproduce in another way. Of course, fixing the bug for future runs is the proper ultimate resolution. Of course, any such forced interrupt/kill/stop of any thread is inherently unsafe and likely to cause other unpredictable inconsistencies. (I'm familiar with all the standard warnings and the reasons for them.) But still, since the only alternative is to kill the JVM process and go through a more lengthy procedure which would result in a less-complete final report, messy/deprecated/dangerous/risky/one-time techniques are exactly what I'd like to try. The JVM is Sun's 1.6.0_16 64-bit on Ubuntu, and the expendable thread is waiting-to-lock an object monitor. Can an OS signal directed to an exact thread create an InterruptedException in the expendable thread? Could attaching with gdb, and directly tampering with JVM data or calling JVM procedures allow a forced-release of the object monitor held by the expendable thread? Would a Thread.interrupt() from another thread generate a InterruptedException from the waiting-to-lock frame? (With some effort, I can inject an arbitrary beanshell script into the running system.) Can the deprecated Thread.stop() be sent via JMX or any other remote-injection method? Any ideas appreciated, the more 'dangerous', the better! And, if your suggestion has worked in personal experience in a similar situation, the best!

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  • LinkedList insert tied to inserted object

    - by wrongusername
    I have code that looks like this: public class Polynomial { List<Term> term = new LinkedList<Term>(); and it seems that whenever I do something like term.add(anotherTerm), with anotherTerm being... another Term object, it seems anotherTerm is referencing the same thing as what I've just inserted into term so that whenever I try to change anotherTerm, term.get(2) (let's say) get's changed too. How can I prevent this from happening?

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  • Wicket: Where to add components? Constructor? Or onBeforeRender?

    - by gmallett
    I'm a Wicket newb. This may just be my ignorance of the Wicket lifecycle so please enlighten me! My understanding is that Wicket WebPage objects are instantiated once and then serialized. This has led to a point of confusion for me, see below. Currently I have a template class which I intend to subclass. I followed the example in the Wicket docs demonstrating how to override the template's behavior in the subclass: protected void onBeforeRender() { add(new Label("title", getTitle())); super.onBeforeRender(); } protected String getTitle() { return "template"; } Subclass: protected String getTitle() { return "Home"; } This works very well. What's not clear to me are the "best practices" for this. It seems like onBeforeRender() is called on every request for the page, no? This seems like there would be substantially more processing done on a page if everything is in onBeforeRender(). I could easily follow the example of the other Wicket examples and add some components in the constructor that I do not want to override, but then I've divided by component logic into two places, something I'm hesitant to do. If I add a component that I intend to be in all subclasses, should I add it to the constructor or onBeforeRender()?

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  • Practicing inserting data into an array by using binary search, few problems

    - by HelpNeeder
    I'm trying to create a method which inserts and then sort elements in form of binary form. The problem I am experiencing that my code doesn't insert data correctly which means that output does not appear to be in order at all. The list is not organized, and data is added in order that is being inserted. Now, 2 questions, what am I doing wrong here? And how to fix this? public void insertBinarySearch(long value) // put element into array { int j = 0; int lower = 0; int upper = elems-1; int cur = 0; while (cur < elems) { curIn = (lower + upper ) / 2; if(a[cur] < value) { j = cur + 1; break; } else if(a[cur] > value) { j = cur; break; } else { if(a[cur] < value) lower = cur + 1; else upper = cur - 1; } } for(int k = elems; k > j; k--) a[k] = a[k-1]; a[j] = value; elems++; }

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