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• Jsp declaration element

  - by Stardust

  <%! class father { static int s = 0; } %> <% father f1 = new father(); father f2 = new father(); f1.s++; out.println(f2.s); // It must print "1" %> When I run the file, I got this error. Can anybody explain? "The field s cannot be declared static; static fields can only be declared in static or top level types"

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• Question about factory classes

  - by devoured elysium

  Currently I have created a ABCFactory class that has a single method creating ABC objects. Now that I think of it, maybe instead of having a factory, I could just make a static method in my ABC Method. What are the pro's and con's on making this change? Will it not lead to the same? I don't foresee having other classes inherit ABC, but one never knows! Thanks

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• ResultSet and aggregation

  - by kachanov

  Ok, I admit my situation is special There is a data system that supports SQL-92 and JDBC interface However the SQL requets are pretty expensive, and in my application I need to retreive the same data multiple times and aggregate it ("group by") on different fields to show different dimensions of the same data. For example on one screen I have three tables that show the same set or records but aggregated by City (1st grid), by Population (2nd grid), by number of babies (3rd grid) This amounts to 3 SQL queries (which is very slow), UNLESS anyone of you can suggest any idea any library from apache commons or from google code, so that I can select all records into ResultSet and get 3 arrays of data group by different fields from this single ResultSet. Am I'm missing some obvious and unexpected solution to this problem?

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• Problem with button addition when double clicking a command label

  - by mistique

  Hy, I got an intersting problem which I stumbled upon. When I double click a label in a JLabel I want to add another button in a JPanel, its a shorter way to make a dragg and drop. The problem is that the button doesn't appears only if i'll position the mouse on the area the button should appear. Why does it happens this way? Anyone got a clue? Are there some thread related issues involved? Thanks in advance

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• What is Chain Matrix Multiplication ?

  - by Hellnar

  Hello, I am trying to understand what is a chain matrix multiplication and how it is different from a regular multiplication. I have checked several sourcers yet all seem to be very academically explained for me to understand. I guess it is a form of dynamic programming algorithm to achieve the operation in an optimised way but I didn't go any further. Thanks

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• Serializing JSON string to object

  - by user1476075

  I am trying to parse through a JSON string and convert it to the following POJO: package apicall; //POJO representation of OAuthAccessToken public class OAuthAccessToken { private String tokenType; private String tokenValue; public OAuthAccessToken(String tokenType,String tokenValue) { this.tokenType=tokenType; this.tokenValue=tokenValue; } public String toString() { return "tokenType="+tokenType+"\ntokenValue="+tokenValue; } public String getTokenValue() { return tokenValue; } public String getTokenType() { return tokenType; } } In order to do this I have written the following code: Gson gson=new Gson(); String responseJSONString="{\"access_token\" : \"2YotnFZFEjr1zCsicMWpAA\",\"token_type\" : \"bearer\"}"; OAuthAccessToken token=gson.fromJson(responseJSONString, OAuthAccessToken.class); System.out.println(token); When I run the code, I get the following output: tokenType=null tokenValue=null Instead of tokenType=bearer tokenValue=2YotnFZFEjr1zCsicMWpAA I dont understand if there's anything I've done wrong. Please help.

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• Fast response on first Socket I/O request but slow every other time when communicating with remote serial port

  - by GreenGodot

  I'm using sockets to pass Serial commands to a remote device. And the response to that request is sent back and printed out. However, I am having a problem in that the first time it is instant but the rest of the time it can take up to 20 seconds to receive a reply. I think the problem is with my attempt at threading but I am not entirely sure. new Thread() { @Override public void run() { System.out.println("opened"); try { isSocketRetrieving.setText("Opening Socket"); socket = new Socket(getAddress(), getRemotePort())); DataOutput = new DataOutputStream(socket .getOutputStream()); inFromServer = new BufferedReader( new InputStreamReader(socket .getInputStream())); String line = ""; isSocketRetrieving.setText("Reading Stream......"); while ((line = inFromServer.readLine()) != null) { System.out.println(line); if (line.contains(getHandshakeRequest())) { DataOutput.write((getHandshakeResponse()toString() + "\r").getBytes()); DataOutput.flush(); DataOutput .write((getCommand().toString() + "\r").getBytes()); DataOutput.flush(); int pause = (line.length()*8*1000)/getBaud(); sleep(pause); } else if (line.contains(readingObject .getExpected())) { System.out.println(line); textArea.append("value = " + line + "\n"); textAreaScroll.revalidate(); System.out.println("Got Value"); break; } } System.out.println("Ended"); try { inFromServer.close(); DataOutput.close(); socket.close(); isSocketRetrieving.setText("Socket is inactive..."); rs232Table.addMouseListener(listener); interrupt(); join(); } catch (IOException e) { e.printStackTrace(); } catch (InterruptedException e) { System.out.println("Thread exited"); } } catch (NumberFormatException e1) { e1.printStackTrace(); } catch (UnknownHostException e1) { e1.printStackTrace(); } catch (IOException e1) { e1.printStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }.start();

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• Unable to implement JMS using ApacheMQ

  - by Galaxin

  Iam trying to implement a simple JMS code in eclipse using ApacheMQ. I have downloaded the ApacheMQ from apache.org and sample JMS sender from SimpleQueueSender and receiver from SimpleQueueReceiver respectively. Now how should i execute this code? I have already gone through all related tutorials but couldnot find answers to these questions. Please suggest solutions on What all are the changes to be done regarding classpaths,settings after the activemq is started as below INFO | jetty-7.1.6.v20100715 INFO | ActiveMQ WebConsole initialized. INFO | Initializing Spring FrameworkServlet 'dispatcher' INFO | ActiveMQ Console at http://0.0.0.0:8161/admin INFO | ActiveMQ Web Demos at http://0.0.0.0:8161/demo INFO | RESTful file access application at http://0.0.0.0:8161/fileserver INFO | Started [email protected]:8161 how to proceed next? 2.Should this server be added in the eclipse as a new server and then the program is run on that server? 3.Can these programs be run from eclipse or should they executed from a separate console?

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• Spring Batch validation

  - by sergionni

  Hello. Does Spring Batch framework provide its specific validation mechanism? I mean, how it's possible to specify validation bean? My validation is result of @NamedQuery - if query returned result, the validation is OK, else - false.

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• Tomcat Http and Https on the same port

  - by Ofri Dagan

  Hi, I have a web-service endpoint and a http connector on port X. At some point this endpoint needs to switch to https, but on the same port! (I know this is not the normal way of doing things, but this is what my clients expect from an old server they are using...) Is there a way to do it in tomcat?

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• Play Framework: Generate PDF from template that uses Javascript for graphing

  - by digiarnie

  I have a template that has some Javascript used to generate graphs in the browser. I would like to use that same template to create a PDF and send as an attachment in an e-mail. In this scenario, there would be no browser/client interaction. I am using the PDF module that is available from the Play website and I have managed to get the PDF rendering to work. The only issue is that the graphs don't show up in the PDF but all other static text does. I'm assuming the graphs aren't appearing in the PDF due to the Javascript not being executed prior to the PDF generation. Does anyone have any ideas on how to get around this problem?

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• which toString() method can be used performance wise??

  - by Mrityunjay

  hi, I am working on one project for performance enhancement. I had one doubt, while we are during a process, we tend to trace the current state of the DTO and entity used. So, for this we have included toString() method in all POJOs for the same. I have now implemented toString() in three different ways which are following :- public String toString() { return "POJO :" + this.class.getName() + " RollNo :" + this.rollNo + " Name :" + this.name; } public String toString() { StringBuffer buff = new StringBuffer("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return buff.toString(); } public String toString() { StringBuilder builder = new StringBuilder("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return builder .toString(); } can anyone please help me to find out which one is best and should be used for enhancing performance.

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• final and private static

  - by xdevel2000

  I read that doing: public final void foo() {} is equals to: private static void foo() {} both meaning that the method is not overridable! But I don't see the equivalence if a method is private it's automatically not accessible...

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• What is annotations and how do it actually works for frameworks like Spring ?

  - by Rachel

  I am new to Spring and now a days I hear a lot about Spring Framework. I have two sets of very specific questions: Set No. 1: What are annotations in general ? How does annotations works specifically with Spring framework ? Can annotations be used outside Spring Framework or are they Framework specific ? Set No. 2: What module of Spring Framework is widely used in Industry ? I think it is Spring MVC but why it is the most used module, if am correct or correct me on this ? I am newbie to Spring and so feel free to edit this questions to make more sense.

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• how to share a variable between two threads

  - by prmatta

  I just inherited some code, two threads within this code need to perform a system task. One thread should do the system task before the other thread. They should not be performing the system task together. The two threads do not have references to each other. Now, I know I can use some sort of a semaphore to achieve this. But my question is what is the right way to get both threads to access this semaphore. I could create a static variable/method a new class : public class SharedSemaphore { private static Semaphore s = new Semaphore (1, true); public static void performSystemTask () { s.acquire(); } public static void donePerformingSystemTask() { s.release(); } } This would work (right?) but this doesn't seem like the right thing to do. Because, the threads now have access to a semaphore, without ever having a reference to it. This sort of thing doesn't seem like a good programming practice. Am I wrong?

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• JAXB Annotated class - setting of a variable which is not an element

  - by sswdeveloper

  I have a JAXB annotated class say @XmlRootElement(namespace = "http://www.abc.com/customer") Class Customer{ @XmlElement(namespace = "http://www.abc.com/customer") private String Name; @XmlElement(namespace = "http://www.abc.com/customer") private String Address; @XmlTransient private HashSet set = new HashSet(); public String getName(){ return Name; } public void setName(String name){ this.Name = name; set.add("Name"); } public String getAddress(){ return Address; } public void setAddress(String address){ this.Address = address; set.add("Address"); } public void getSet(){ return set; } I have a XML of the form <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <Customer xmlns="http://www.abc.com/customer" > <Name>Ralph</Name> <Address>Newton Street</Address> </Customer> I use JAXB unmarshalling to get the object representation of the XML input. The values for Name and Address are set correctly. However the value of set gets lost(since it is @XMLTransient it gets ignored) Is there any way of ensuring that it is still set in the object which has been unmarshalled? Some other annotation which I can use?

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• Duplicate Prefix Error in Jsp page with Struts

  - by Cricandcric.com

  Hi, i am creating and Configuring the Struts for the first time, when I place the following Code in my jsp page <%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%> <%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%> <%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%> <%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles"%> I am getting the error when i move the mouse over the 1st Line "Duplicate Prefix "html" When I move the mouse over the 2nd Line, I am getting as "Duplicate Prefix "html" Similarly for 3rd and 4th Line, Can any one tell me why is this error all about Thanks in advance

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• Primary reasons why programming language runtimes use stacks?

  - by manuel aldana

  Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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• Use ObjectOutputStream and FileOutputStream with FileWriter

  - by wishi

  Hi! Is there any way to use ObjectOutputStream like this: <tag>output of the ObjectOutputStream</tag> If I try: FileOutputStream fos = new FileOutputStream(filename); ObjectOutputStream oos = new ObjectOutputStream(fos); FileWriter fw = new FileWriter(fos); And for example: fw.write("<tag>"); oos.write(cool_object); fw.wrote("</tag>"); I don't get that result. It seems the ObjectOutputStream overwrites the file completly each and every time.

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• Pointing layout_above to an external ID?

  - by Joren

  When I try to use layout_above to position a view above another view, it can't find the ID if it's not in the same XML file. I'm adding my XML files at run time but I still want to be able to position them relative to eachother. Any suggestions?

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• Hibernate - get the size of a list in a property

  - by mada

  I have a class A which have a list of B elements. In my A class i would like to add: int size; which will be valued with the number of B elements. So when I would call myA.getSize() I will have it. Is it possible to map a count query with a single property in the hibernate mapping? I don't want to load the list that is why i would like to add a size property.

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• Is it possible to have Ant print out the classpath for a particular target? If so, how?

  - by Daryl Spitzer

  I'm trying to get a target to build that has quite a long list of <pathelement location="${xxx}"/> and <path refid="foo.class.path"/> elements in its <path id="bar.class.path"> element (in the build.xml file). I keep getting "package com.somecompany.somepackage does not exist" errors, and I'm having a hard time chasing down these packages and making sure I've synced them from our repository. I'm new to this team so I'm unfamiliar with the build, but I would prefer to figure this out myself if possible (so I don't bother the other very busy team members). I have very limited experience with Ant. I think it would save me quite a bit of time if I could have Ant print out the classpath for the target I'm trying to build.

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• ExecutorSerrvice memory leak on exception

  - by TofuBeer

  I am having a hard time tracking this down since the profiler keeps crashing (hotspot error). Before I go too deep into figuring it out I'd like to know if I really have a problem or not :-) I have a few thread pools created via: Executors.newFixedThreadPool(10); The threads connect to different web sites and, on occasion, I get connection refused and wind up throwing an exception. When I later on call Future.get() to get the result it will then catch the ExecutionException that wraps the exception that was thrown when the connection could not be made. The program uses a fairly constant amount of memory up until the point in time that the exceptions get thrown (they tend to happen in batches when a particular site is overloaded). After that point the memory again remains constant but at a higher level. So my question is along the lines of is the memory behaviour (reported by "top" on Unix) expected because the exceptions just triggered something or do I probably have an actual leak that I'll need to track down? Additionally when Future.get() throws an exception is there anything else I need to do besides catch the exception (such as call Future.cancel() on it)?

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• Implement the business logic in an app server with spring

  - by HenryOS

  Hi everybody, i have a doub... Is posible implement the business logic in an App Server remote using pojos instead of either EJB or Servlets???. The main idea is apply a model of 3 layers where the clients may be both web browsers and desktop applications, and they share the business logic in an App Server. Sorry for my english... im from Argentina and my english is poor. Thank you to everybody and i hope that anybody can help me soon. Regards! this would be the architecture browser----- Web Server --------|App Server(Business Logic common)|-------|RDBMS common| desktop App(Swing for example)-|App Server(Business Logic common)|-------|RDBMS common|

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• How to write a jUnit test for this class?

  - by flash

  Hi, I would like to know what's the best approach to test the method "pushEvent()" in the following class with a jUnit test. My problem is, that the private method "callWebsite()" always requires a connection to the network. How can I avoid this requirement or refactor my class that I can test it without a connection to the network? class MyClass { public String pushEvent (Event event) { //do something here String url = constructURL (event); //construct the website url String response = callWebsite (url); return response; } private String callWebsite (String url) { try { URL requestURL = new URL (url); HttpURLConnection connection = null; connection = (HttpURLConnection) requestURL.openConnection (); String responseMessage = responseParser.getResponseMessage (connection); return responseMessage; } catch (MalformedURLException e) { e.printStackTrace (); return e.getMessage (); } catch (IOException e) { e.printStackTrace (); return e.getMessage (); } } }

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