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  • garbage collector Issue

    - by Eslam
    this question is like my previous one Given: 3. interface Animal { void makeNoise(); } 4. class Horse implements Animal { 5. Long weight = 1200L; 6. public void makeNoise() { System.out.println("whinny"); } 7. } 8. public class Icelandic extends Horse { 9. public void makeNoise() { System.out.println("vinny"); } 10. public static void main(String[] args) { 11. Icelandic i1 = new Icelandic(); 12. Icelandic i2 = new Icelandic(); 13. Icelandic i3 = new Icelandic(); 14. i3 = i1; i1 = i2; i2 = null; i3 = i1; 15. } 16. } When line 14 is reached, how many objects are eligible for the garbage collector? A. 0 B. 1 C. 2 D. 3 E. 4 F. 6 i choosed A but the right answer is E, but i don't know Why?

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  • NetBeans open project problem.

    - by rgksugan
    I created a NetBeans project. I took the project folders zipped to another machine and tried opening it in NetBeans. NetBeans didn't identify it as a NetBeans project. I have transfered projects in this way before but why is it not working now? Are any of my project files corrupted. Is there any way to retrieve my files from this?

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  • Junit exception test

    - by Prithis
    I have two tests to check the expected exception throw. I am using Junit 4 and has following syntax. @Test(expected=IllegalArgumentException.class) public void testSomething(){ .......... } One of the tests fail even though IllegalArgumentException is thrown and the other passes. Any idea whats missing?? I modified the test which is failing to following and it passes. public void testSomething(){ try{ ............ //line that throws exception fail(); }catch(IllegalArgumentException e) { } }

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  • ExecutionException and InterruptedException while using Future class's get() method

    - by java_geek
    ExecutorService executor = Executors.newSingleThreadExecutor(); try { Task t = new Task(response,inputToPass,pTypes,unit.getInstance(),methodName,unit.getUnitKey()); Future<SCCallOutResponse> fut = executor.submit(t); response = fut.get(unit.getTimeOut(),TimeUnit.MILLISECONDS); } catch (TimeoutException e) { // if the task is still running, a TimeOutException will occur while fut.get() cat.error("Unit " + unit.getUnitKey() + " Timed Out"); response.setVote(SCCallOutConsts.TIMEOUT); } catch (InterruptedException e) { cat.error(e); } catch (ExecutionException e) { cat.error(e); } finally { executor.shutdown(); } } How should i handle the InterruptedException and ExecutionException in the code? And in what cases are these exceptions thrown?

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  • How do i change this method to get strings instead of ints

    - by David
    here is the original code: public static int getInt () { Scanner in = new Scanner (System.in) ; if (in.hasNextInt()) { int a = in.nextInt() ; return a ; } else { System.out.println ("try again:") ; return getInt () ; } } This checks and sees if the input it receives is an int. If it is then it returns the int, if not it tells you to try again and re-runs. This is what i tried to do to change it: public static String getIns () { Scanner in = new Scanner (System.in) ; if (in.hasNextString()) { String a = in.nextString() ; return a ; } else { System.out.println ("try again:") ; return getIns () ; } } This doesn't work though. I looked through the documentation for the scanner class and i think the problem is that there is no such method as in.hasNextString or in.nextString What methods from the scanner class can i use to do what i intend these to do?

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  • Netbeans Clamshell emulator out of memory

    - by Kyle
    Hello, I have been working with the clamshell mobile phone emulator for netbeans. I recently have tested a simple bluetooth application and got an Out of Memory erorr. Is it possible to up the amount of memory the emulator can use? thanks!

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  • Magi squares, recursive

    - by user310827
    Hi, my problem is, I'm trying to permute all posibilities for 3x3 square and check if the combination is magic. I've added a tweak with (n%3==0) if statement that if the sum of numbers in row differs from 15 it breaks the creation of other two lines... but it doesn't work, any suggestions, I call the function with Permute(1). public static class Global { //int[] j = new int[6]; public static int[] a= {0,0,0,0,0,0,0,0,0}; public static int[] b= {0,0,0,0,0,0,0,0,0}; public static int count = 0; } public static void Permute(int n) { int tmp=n-1; for (int i=0;i<9;i++){ if (Global.b[i]==0 ) { Global.b[i]=1; Global.a[n-1]=i+1; if ((n % 3) == 0) { if (Global.a[0+tmp]+Global.a[1+tmp]+Global.a[2+tmp] == 15) { if (n<9) { Permute(n+1); } else { isMagic(Global.a); } } else break; } else { Permute(n+1); } Global.b[i]=0; } } }

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  • Why do I not see stricter scoping more often?

    - by Ben
    I've found myself limiting scope fairly often. I find it makes code much clearer, and allows me to reuse variables much more easily. This is especially handy in C where variables must be declared at the start of a new scope. Here is an example of what I mean. { int h = 0; foreach (var item in photos) { buffer = t.NewRow(); h = item.IndexOf("\\x\\"); buffer["name"] = item.Substring(h, item.Length - h); t.Rows.Add(buffer); } } With this example, I've limited the scope of h, without initializing it in every iteration. But I don't see many other developers doing this very often. Why is that? Is there a downside to doing this?

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  • How to find the Mac address of a 'shutdown' system on local lan (is it possible?)

    - by pirates-iiita
    hello everyone, Can anyone please tell the way to find out the mac address of a system which is: Shutdown Power plugged in Connected to Lan Nic card ON. Kindly post the solution as i urgently need it in my project... thank you Update I am asking how to find out the mac address of some other system which is already shutdown.... and which is on lan.. I want to find out its mac from my system.... and to be clear... i want to tell that.. arp table can be populated by using ping .. i.e. if 172.16.3.12 is not in arp table then it can be added by just ping 172.16.3.12 but a system can be pinged only if its on ... a shutdown system can't be pinged...

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  • Servlet request getparameter's performance

    - by Bob
    Hi, I noticed that my app is very slow sometimes, so I've done some tests. It's a very simple web app. One servlet gets some parameters than stores them. Everything's fine except one thing. It takes too long to get a parameter for the first time. It doesn't matter which parameter I try to get, but for the first time it is very slow. The strange thing is this doesn't happen always. Sometimes getting a parameter for the first time is not slow. My code looks like this request.getParameter("paramName"); request.getParameter("paramName2"); request.getParameter("paramName3"); Getting "paramName" is slow. Getting the others is very fast. By slow I mean : 200-800 millisec By very fast I mean: ~0 millisec (in the code snippet, I didn't write the performance test, but I'm using System.currentTimeMillis())

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  • Best way to detect duplicates when using Spring Hibernate Template

    - by Dean Povey
    We have an application which needs to detect duplicates in certain fields on create. We are using Hibernate as our persistence layer and using Spring's HibernateTemplate. My question is whether it is better to do so an upfront lookup for the item before creating, or to attempt to catch the DataIntegrityViolation exception and then check if this is caused by a duplicate entry.

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  • Stub web calls in Scala

    - by Dennis Laumen
    I'm currently writing a wrapper of the Spotify Metadata API to learn Scala. Everything's fine and dandy but I'd like to unit test the code. To properly do this I'll need to stub the Spotify API and get consistent return values (stuff like popularity of tracks changes very frequently). Does anybody know how to stub web calls in Scala, the JVM in general or by using some external tool I could hook up into my Maven setup? PS I'm basically looking for something like Ruby's FakeWeb... Thanks in advance!

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  • Restrict number of lines in html JLabel

    - by Mike
    I have a JLabel that needs to display some html-formatted text. However, I want to restrict this to being 4 lines long (and if so, provide a button to see everything). So far, I've tried setting the maximum size manually or via a layout manager. However, both of these solutions can cause part of a line to be displayed.

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  • How can I get jsonp to play nice with my class?

    - by George Edison
    This whole jsonp thing is quite confusing... Here is what I want to do: I have a class DataRetriever The class has a method GetData GetData makes a jsonp request with the following code: var new_tag = document.createElement('script'); new_tag.type = 'text/javascript'; new_tag.src = 'http://somesite.com/somemethod?somedata'; // Add the element var bodyRef = document.getElementsByTagName("body").item(0); bodyRef.appendChild(new_tag); Now, the jsonp data from the server somesite.com can call a function in my code with the data. The problem is, how does the data get delivered to the instance of DataRetriever that requested it? I'm really stuck here.

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  • JTextArea thread safe?

    - by Dhaivat Pandya
    Hello everyone, I have some code that does some initialization (including making a JTextArea object), starts three seperate threads, and then these threads try to update the JTextArea (i.e. append() to it), but its not working at all. Nothing shows up on the JTextArea (however, during the initialzation, I print some test lines onto it, and that works fine). What's going on? How can I fix this? Also, each of those threads sleeps a random amount of time every time it has to update the JTextArea. Sorry I haven't provided any code, its all spread out over several files.

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  • Trying to create spring project with maven

    - by Gandalf StormCrow
    Hello everyone I was just going trough http://static.springsource.org/docs/Spring-MVC-step-by-step/part1.html spring tutorial, and I thought its old I'll think something better on my own. For starters how do I start spring project with maven, which archtype should I choose? I wanna create simple spring app, write class which I will deploy to jboss, spring will instansiate it at startup .. that is what have in mind for now .. for now I need to start it first

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  • Refactored App Engine project - now Eclipse is infinitely building the project without end

    - by Yog
    I renamed some files in my App Engine project and refactored code, changing references to variables. Everything seemed fine until I changed the references in the web.xml for the project. Then I got a complaint about some error with the DataNucleus enhancer and now the project build process is stuck at 22%. I tried stopping Eclipse and restarting but the build process keeps hanging. Any tips on how to clean out whatever it's getting stuck on?

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  • Parse Nested XML tags with the same name

    - by footose
    Let's take a simple XML document: <x> <e> <e> <e>Whatever 1</e> </e> </e> <e> <e> <e>Whatever 2</e> </e> </e> <e> <e> <e>Whatever 3</e> </e> </e> </x> Using the standard org.w3c.dom, I can get the nodes in X by doing.. NodeList fullnodelist = doc.getElementsByTagName("x"); But if I want to return the next set of "e" I try to use something like .. Element element = (Element) fullnodelist.item(0); NodeList nodes = pelement.getElementsByTagName("e"); Expecting it to return "3" nodes (because there are 3 sets of "e"), but instead, it returns "9" - becuase it gets all entries with "e" apperently. This would be fine in the above case, because I could probably iterate through and find what I'm looking for. The problem I'm having is that when the XML file looks like the following: <x> <e> <pattern>whatever</pattern> <blanks> <e>Something Else</e> </blanks> </e> <e> <pattern>whatever</pattern> <blanks> <e>Something Else</e> </blanks> </e> </x> When I request the "e" value, it returns 4, instead of (what i expect) 2. Am I just not understanding how the DOM parsing works? Typically in the past I have used my own XML documents so I would never name the items like this, but unfortunately this is not my XML file and I have no choice to work like this. What I thought I would do is write a loop that "drills down" nodes so that I could group each node together... public static NodeList getNodeList(Element pelement, String find) { String[] nodesfind = Utilities.Split(find, "/"); NodeList nodeList = null; for (int i = 0 ; i <= nodesfind.length - 1; i++ ) { nodeList = pelement.getElementsByTagName( nodesfind[i] ); pelement = (Element)nodeList.item(i); } // value of the nod we are looking for return nodeList; } .. So that if you passed "s/e" into the function, it would return the 2 nodes that I'm looking for (or elements, maybe I'm using the terminology incorrect?). instead it returns all of the "e" nodes within that node. I'm using J2SE for this, so options are rather limited. I can't use any third party XML Parsers. Anyway, if anyone is still with me and has a suggestion, it would be appreciated.

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  • Transactions in hibernate

    - by kumar1425
    Hi I new to hibernate In my project, i need to handle transactions. How to handle declarative transactions with in two classes Examples: //class 1 class A{ createA() { insert(A); } } //class 2 class B { createB() { insert(B); } } //class 3 @Transaction(Exception.class) class C { test() { create(A); create(B); } } As per the above code is there any possibility to handle transactions, in such a way that if the insert in classA success and the insert in the classB fails then the transaction should rollback and remove the record inserted in the table A corresponding to the Class A please help me with this using declarative transactions.... Thanks in adavace....

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  • Large ResultSet on postgresql query

    - by tuler
    I'm running a query against a table in a postgresql database. The database is on a remote machine. The table has around 30 sub-tables using postgresql partitioning capability. The query will return a large result set, something around 1.8 million rows. In my code I use spring jdbc support, method JdbcTemplate.query, but my RowCallbackHandler is not being called. My best guess is that the postgresql jdbc driver (I use version 8.3-603.jdbc4) is accumulating the result in memory before calling my code. I thought the fetchSize configuration could control this, but I tried it and nothing changes. I did this as postgresql manual recomended. This query worked fine when I used Oracle XE. But I'm trying to migrate to postgresql because of the partitioning feature, which is not available in Oracle XE. My environment: Postgresql 8.3 Windows Server 2008 Enterprise 64-bit JRE 1.6 64-bit Spring 2.5.6 Postgresql JDBC Driver 8.3-603

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  • JBoss Clustered Service that sends emails from txt file

    - by michael lucas
    I need a little push in the right direction. Here's my problem: I have to create an ultra-reliable service that sends email messages to clients whose addresses are stored in txt file on FTP server. Single txt file may contain unlimited number of entries. Most often the file contains about 300,000 entries. Service exposes interface with just two simple methods: TaskHandle sendEmails(String ftpFilePath); ProcessStatus checkProcessStatus(TaskHandle taskHandle); Method sendEmails() returns TaskHandle by which we can ask for ProcessStatus. For such a service to be reliable clustering is necessary. Processing single txt file might take a long time. Restarting one node in a cluster should have no impact on sending emails. We use JBoss AS 4.2.0 which comes with a nice HASingletonController that ensure one instance of service is running at given time. But once a fail-over happens, the second service should continue work from where the first one stopped. How can I share state between nodes in a cluster in such a way that leaves no possibility of sending some emails twice?

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  • Using thread inter-communication to increase my server app's IO throughput; not sure how

    - by Howard Guo
    My server application creates a new thread for each incoming connection. Incoming requests are serialized in a BlockingQueue. There is one worker thread taking items from the queue, produce a response and send the response through socket. I have noticed a throughput issue: Currently, worker thread is responsible of sending the response message through socket, thus severely wasting processing power and throughput. I am considering: rather than sending the response itself, why not telling network IO threads to send the response? However, when I think about thread inter-communication, I cannot yet figure out how to approach it: Worker thread will produce a response, but how will it inform the response message to IO thread? Is there a standard/best practice? Thank you.

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  • Return value changed after finally

    - by Nestor
    I have the following code: public bool ProcessData(String data) { try { result= CheckData(data); if (TextUtils.isEmpty(result)) { summary="Data is invalid"; return false; } ... finally { Period period = new Period(startTime, new LocalDateTime()); String duration = String.format("Duration: %s:%s", period.getMinutes(), period.getSeconds()); LogCat(duration); } return true; As I learned from this question, the finally block is executed after the return statement. So I modified my code according to that, and in the finally I inserted code that does not modify the output. Strangely, the code OUTSIDE the finally block does. My method always returns true. As suggested, it is not a good idea to have 2 return. What should I do?

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