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  • How do I check that an entity is unreferenced in JPA?

    - by Martin
    I have the following model @Entity class Element { @Id int id; @Version int version; @ManyToOne Type type; } @Entity class Type { @Id int id; @Version int version; @OneToMany(mappedBy="type") Collection<Element> elements; @Basic(optional=false) boolean disabled; } and would like to allow Type.disabled = true only if Type.elements is empty. Is there a way to do it atomically? I would like to prevent an insertion of an Element in a transaction while the corresponding Type is being disabled by an other transaction.

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  • delete hibernate entity question?

    - by ylazez
    i want to delete a row and cascade all foreign keys in hibernate i am new to hibernate and i want to know if there's a method to delete an entity session.delete(); like the session.save and session.update methods in hibernate?

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  • Interrupt a thread in DatagramSocket.receive

    - by SEK
    I'm building an application that listens on both TCP and UDP, and I've run into some trouble with my shutdown mechanism. When I call Thread.interrupt() on each of the listening threads, the TCP thread is interrupted from listening, whereas the UDP listener isn't. To be specific, the TCP thread uses Socket.accept(), which simply returns (without actually connecting). Whereas the UDP thread uses DatagramSocket.receive, and doesn't exit that method. Is this an issue in my JRE, my OS, or should I just switch to (Datagram)Socket.close()?

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  • Rotated image in ImageView

    - by Lars D
    I want to show an arrow that indicates the direction towards a goal, using the orientation sensor and current GPS position. Everything works well, except that I want to rotate the arrow image in my ImageView. The current code, which shows the arrow pointing upwards, is this: ImageViewArrow.setImageResource(R.drawable.arrow); What is the best solution for showing the arrow, rotated by N degrees?

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  • Please explain how Trial Division works for Primality Test

    - by mister_dani
    I came across this algorithm for testing primality through trial division I fully understand this algorithm static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i <= Math.sqrt(N); i++) if (N % i == 0) return false; return true; } It works just fine. But then I came across this other one which works just as good but I do not fully understand the logic behind it. static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i * i<N; i++) if (N % i == 0) return false; return true; } It seems like i *i < N behaves like i <= Math.sqrt(N). If so, why?

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  • Is it possible to use JSF+Facelets with HTML 4/5?

    - by Bytecode Ninja
    Facelets relies on XML namespaces to work with XHTML. How are HTML 4, and as far as I know, HTML 5 do not support namespaces. Also HTML 5 has some new elements that are not available in XHTML. Even HTML 4 and XHTML have some differences regarding elements and attributes they support. The question is: Is it possible to render HTML 4/5 documents using Facelets? If so, how?

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  • Simple servlet or filter to process form

    - by David
    Is there a simple framework for processing form submissions via a servlet? For my needs, a framework like STRUTS seems like over kill. My ideal processor would be a servlet that converts form elements into a bean object, possibly using typing information in the form to help with the conversion. Does something like this exist or is there another solution out there geared toward simpler needs? Thanks!

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  • Is it possible to draw simultaneously on a panel?

    - by swift
    I have to develop a whiteboard application in which both the local user and the remote user should be able to draw simultaneously, is this possible? If possible then any logic? I have already developed a code but in which i am not able to do this, when the remote user starts drawing the shape which i am drawing is being replaced by his shape and co-ordinates. This problem is only when both draw simultaneously. any idea guys?

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  • Sending message to multiple contacts of mobile by providing search facility in J2ME

    - by learn
    I wan to send the message to multiple contacts in the contactlist for(int j=0;j<vector.size();j++){ listofContacts=new ListofContacts(); listofContacts=(ListofContacts)vector.elementAt(j); list.setFitPolicy(1); list.append(listofContacts.contactname + " "+ listofContacts.contactno,null); System.out.println(listofContacts.contactname + " "+ listofContacts.contactno); } here i have taken all the contacts of contact list in vector and the listofcontacts is the class containing the name and number. To show the list of contacts for selection i am using list control with multiple choice. The code is working fine and message is sent to all the contacts which are selected by the user but as we know there may be 1000 of contacts in phonebook and in these case to select a particular user we have to scroll down the list. Now how to keep the search facility so that we can directly go to the required contact and if it is not possible with the list control which control is to be used so that multiple contacts can be selected and also search facility is available.

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  • Indexing through Android string resources

    - by gssi
    OK, I've got the code to allow me to index through the string resources. Now, how do I get the value of a specific resource item without knowing its name? Here's the index loop: Field[] fLst = R.string.class.getFields(); for(Field f : fLst){ Log.i(dbgTag, "Field Entry: R.string." + f.getName()); } Thanks for your efforts ...

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  • Create table class as a singleton

    - by Mark
    I got a class that I use as a table. This class got an array of 16 row classes. These row classes all have 6 double variables. The values of these rows are set once and never change. Would it be a good practice to make this table a singleton? The advantage is that it cost less memory, but the table will be called from multiple threads so I have to synchronize my code which way cause a bit slower application. However lookups in this table are probably a very small portion of the total code that is executed. EDIT: This is my code, are there better ways to do this or is this a good practice? Removed synchronized keyword according to recommendations in this question. final class HalfTimeTable { private HalfTimeRow[] table = new HalfTimeRow[16]; private static final HalfTimeTable instance = new HalfTimeTable(); private HalfTimeTable() { if (instance != null) { throw new IllegalStateException("Already instantiated"); } table[0] = new HalfTimeRow(4.0, 1.2599, 0.5050, 1.5, 1.7435, 0.1911); table[1] = new HalfTimeRow(8.0, 1.0000, 0.6514, 3.0, 1.3838, 0.4295); //etc } @Override @Deprecated public Object clone() throws CloneNotSupportedException { throw new CloneNotSupportedException(); } public static HalfTimeTable getInstance() { return instance; } public HalfTimeRow getRow(int rownumber) { return table[rownumber]; } }

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  • Is it more secure to run a desktop app in a applet?

    - by Tom Brito
    Fist of all, when I say "run a desktop app in a applet" I mean do a Applet application that runs off-line, instead of a Desktop application that runs inside a JFrame. The little I know about applets (and maybe something I say is wrong, please correct me) is that applets have all permitions not granted by default. Also, the applets run inside a Sandbox, that does not allow information in or out without explicity permition. So, if I am focused on security in my application, its best to run it inside an applet (off-line, for a desktop application) then inside a JFrame. Is it right?

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  • How to find the largest power of 2 less than the given number

    - by nazar_art
    I need to find the largest power of 2 less than the given number. And I stuck and can't find any solution. Code: public class MathPow { public int largestPowerOf2 (int n) { int res = 2; while (res < n) { res =(int)Math.pow(res, 2); } return res; } } This doesn't work correctly. Testing output: Arguments Actual Expected ------------------------- 9 16 8 100 256 64 1000 65536 512 64 256 32 How to solve this issue?

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  • Censoring selected words (replacing them with ****) using a single replaceAll?

    - by aioobe
    I'd like to censor some words in a string by replacing each character in the word with a "*". Basically I would want to do String s = "lorem ipsum dolor sit"; s = s.replaceAll("ipsum|sit", $0.length() number of *)); so that the resulting s equals "lorem ***** dolor ***". I know how to do this with repeated replaceAll invokations, but I'm wondering, is this possible to do with a single replaceAll?

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  • Should i use lock.lock(): in this method?

    - by user962800
    I wrote this method whose purpose is to give notice of the fact that a thread is leaving a specific block of code A thread stands for a car which is leaving a bridge so other cars can traverse it . The bridge is accessible to a given number of cars (limited capacity) and it's one way only. public void getout(int diection){ // release the lock semaphore.release(); try{ lock.lock(); //access to shared data if(direction == Car.NORTH) nNordTraversing--; //decreasing traversing threads else nSudTraversing--; bridgeCond.signal(); }finally{ lock.unlock(); } } My question is: should I use lock.lock(); or it's just nonsense? thanks in advance

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  • Read a file to multiple array byte[]

    - by hankol
    I have an encryption algorithm (AES) that accepts file converted to array byte and encrypt it. Since I am going to process a very big size files, the JVM may go out of memory. I am planing to read the files in multiple array byte. each containing some part of the file. Then I teratively feed the algorithm. Finally merge them to produce encrypted file. So my question is: there any way to read a file part by part to multiple array byte? I thought I can use the following to read the file to array byte: IOUtils.toByteArray(InputStream input). And then split the array into multiple bytes using: Arrays.copyOfRange(). But I am afraid that the first code that reads file to byte will make the JVM to go out of memory. any suggestion please ? thanks

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  • Iterating over a String to check for a number and printing out the String value if it doesn't have a number

    - by wheelerlc64
    I have set up my function for checking for a number in a String, and printing out that String if it has no numbers, and putting up an error message if it does. Here is my code: public class NumberFunction { public boolean containsNbr(String str) { boolean containsNbr = false; if(str != null && !str.isEmpty()) { for(char c : str.toCharArray()) { if(containsNbr = Character.isDigit(c)) { System.out.println("Can't contain numbers in the word."); break; } else { System.out.println(str); } } } return containsNbr; } } import com.imports.validationexample.function.NumberFunction; public class Main { public static void main(String[] args) { NumberFunction nf = new NumberFunction(); System.out.println(nf.containsNbr("bill4")); } } I am trying to get it to print out the result to the console, but the result keeps printing multiple times and prints the boolean value, which I do not want, something like this: bill4 bill4 bill4 bill4 Can't contain numbers in the word. true Why is this happening? I've tried casting but that hasn't worked out either. Any help would be much appreciated.

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  • Check and avoid if a char is being entered in a int

    - by John
    Hi.... This is a exremely stupid question but i need help with this.... I'm trying to make a small program that i made robust and needed some help with tht.... int num1; int num2 = 0; System.out.print("Enter number 1: "); num1 = kb.nextInt(); while(num2<num1) { System.out.print("Enter number 2: "); num2 = kb.nextInt(); } Number 2 has to be greater than number 1 Also i want the program to automatically check and ignore if the user enters a char instead of an int... Cause right now when a user enters lets say "r" instead of a number the program just exists....

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  • How to turn off Eclipse console on Windows

    - by engfer
    So I change the -vm argument for eclipse.exe using the eclipse.ini settings file, and now there's an command prompt console (even if I remove the -vm value). Does anyone know how to turn off the console so I only have the eclipse GUI and not the console window? I'm running MS Windows 7.

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