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• Performance implications of finalizers on JVM

  - by Alexey Romanov

  According to this post, in .Net, Finalizers are actually even worse than that. Besides that they run late (which is indeed a serious problem for many kinds of resources), they are also less powerful because they can only perform a subset of the operations allowed in a destructor (e.g., a finalizer cannot reliably use other objects, whereas a destructor can), and even when writing in that subset finalizers are extremely difficult to write correctly. And collecting finalizable objects is expensive: Each finalizable object, and the potentially huge graph of objects reachable from it, is promoted to the next GC generation, which makes it more expensive to collect by some large multiple. Does this also apply to JVMs in general and to HotSpot in particular?

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• What is the difference between the Facade and Adapter Pattern?

  - by devoured elysium

  I've been reading both definitions and they seem quite the same. Could anyone point out what are their differences? Thanks

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• Tomcat does not persist UserPrincipal during restart

  - by mabuzer

  How to force Tomcat to serialize UserPrincipal so that the user is kept logged in when Tomcat has restarted? Right now the user has to login again everytime.

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• Using enums or a set of classes when I know I have a finite set of different options?

  - by devoured elysium

  Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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• Compare Long values Struts2

  - by Marquinio

  Hi everyone I'm trying to compare two values using struts2 s:if tag but its not working. If I hardcode the values it works but I want it to be dynamic. The variable stringValue is of type String. The variable currentLongValue is of type Long. <s:set var="stringValue" value="order"/> <s:iterator value="listTest"> <s:set var="currentLongValue" value="value"/> <s:if test="#currentLongValue.toString() == #stringValue" > //Do something </s:if> <s:else> //Do something else </s:else> </s:iterator> For the s:if I have tried toString and also the equals(). It only works if I hardcode the values. Example: <s:if test="#currentLongValue == 1234"> Any clues? Thank you.

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• Pointers, links, object and reference count

  - by EugeneP

  String a = "a"; // allocate memory and write address of a memory block to a variable String b = "b"; // in a and b hold addresses b = a; // copy a address into b. // Now what? b value is completely lost and will be garbage collected //* next step a = null; // now a does not hold a valid address to any data, // still data of a object exist somewhere, yet we cannot get access to it. Correct me if there's a mistake somewhere in my reflexions. My question is: suppose anInstance object of type Instance has a property ' surname ' anInstance.getSurname() returns "MySurname". now String s = anInstance.getSurname(); anInstance = null; question is - is it true that getSurname value, namely MySurname will not be garbage collected because and only because it has active reference counter 0, and if other properties of anInstance have a zero reference counter, they'll be garbage collected?

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• h:graphicimage not working in c:foreach

  - by Muneeswaran Balasubramanian

  I have used c:forEach loop for display the list of images using h:graphicImage. But I can't display the images. I have the h:commandLink also in my page. The image have to be displayed at the time of form inititalization. But its not working. But after click the h:commandlink, the images are displayed properly. Before that it shows the image not found text (alt message). I have used h:graphicImage tag like below <c:forEach items="#{Sample.imageList}" var="images" varstatus="imageStatus"> <h:graphicimage id="image" url="#{images}" alt="Image Not Found"/> </c:forEach> What I do wrong in that and how can I achieve that?

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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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• If I want to use a specific font that I know it is not available in most of the user's computer

  - by mayur

  Hi All, If I want to use a specific font that I know it is not available in most of the user's computer, is it possoble to embed the font in my web site in some way? I have gone to some web site using special fonts as text, but not as image. I wonder how it works. Thanks Mayur

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• Hibernate/JPA DB Schema Generation Best Practices

  - by Bytecode Ninja

  I just wanted to hear the opinion of Hibernate experts about DB schema generation best practices for Hibernate/JPA based projects. Especially: What strategy to use when the project has just started? Is it recommended to let Hibernate automatically generate the schema in this phase or is it better to create the database tables manually from earliest phases of the project? Pretending that throughout the project the schema was being generated using Hibernate, is it better to disable automatic schema generation and manually create the database schema just before the system is released into production? And after the system has been released into production, what is the best practice for maintaining the entity classes and the DB schema (e.g. adding/renaming/updating columns, renaming tables, etc.)? Thanks in advance.

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• Which use cases make temporary JMS queues a better choice than persistent queues?

  - by Stephen Harmon

  When you are designing a JMS application, which use cases make you pick temporary queues over persistent queues? We use temporary queues for response messages. We're having some issues maintaining connections to the temp queues, though, so I am testing persistent response queues, instead. One clear disadvantage of persistent queues is that your application has to "know" about them beforehand. If that's not a big deal, though, are there use cases where temp queues are the obvious choice?

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• Function to calculate power , number , any thing about Signal of routing

  - by sultan

  ples , help me , i need answer of this questions :( i need function in any language to calculate power of signal in routing thanks :)

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• stop thread that does not get interrupted

  - by prmatta

  I have a thread that sits and reads objects off of an ObjectInputStream: public void run() { try { ois = new ObjectInputStream(clientSocket.getInputStream()); Object o; while ((o = ois.readObject()) != null) { //do something with object } } catch (Exception ex) { //Log exception } } readObject does not throw InterruptedException and as far as I can tell, no exception is thrown when this thread is interrupted. How do I stop this thread?

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• inserted in multiple tables of database at a time

  - by rajkumari

  can we work with multiple tables of database with same connection object of database at same time . suppose i have inserted value in table 1 and at same time also inserted value in table 2 of data base with same object of data base connection. I am using sqlite database in code and getting database locked exception while commit() .

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• Using HSQLDB in production environments

  - by lewap

  I want to use HSQLDB in a production environment for stroring some data in memory and for data export using files. Does anybody have experience with using hsqldb in production environments? Is hsqldb treating server resources gracefully and does it cleanup unused resources properly?

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• Beautifying a SWT application on Mac

  - by Mark

  SWT is designed to be cross-platform, so it can run on a Mac. The problem is it commits the cardinal sin of Macland - it's UGLY. Toolbars don't look like Mac toolbars, status bars don't look like Mac status bars, etc. Does anyone have any experience in making an SWT application look more like a Mac application? For example, by making platform-specific JNI calls via the 'OS' class in SWT? If so, how difficult was it? (This question arises because we are looking at porting an existing SWT app designed to run on Windows) Thanks

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• log4j rootLogger seems to inherit log level of other logger. Why?

  - by AndrewR

  I've got a log4J setup in which the root logger is supposed to log ERROR level messages and above to the console and another logger logs everything to syslog. log4j.properties is: # Root logger option log4j.rootLogger=ERROR,R log4j.appender.R=org.apache.log4j.ConsoleAppender log4j.appender.R.layout=org.apache.log4j.PatternLayout log4j.appender.R.layout.ConversionPattern=%d %p %t %c - %m%n log4j.logger.SGSearch=DEBUG,SGSearch log4j.appender.SGSearch=org.apache.log4j.net.SyslogAppender log4j.appender.SGSearch.SyslogHost=localhost log4j.appender.SGSearch.Facility=LOCAL6 log4j.appender.SGSearch.layout=org.apache.log4j.PatternLayout log4j.appender.SGSearch.layout.ConversionPattern=[%-5p] %m%n In code I do private static final Logger logger = Logger.getLogger("SGSearch"); . . . logger.info("Commencing snapshot index [" + args[1] + " -> " + args[2] + "]"); What is happening is that I get the console logging for all logging levels. What seems to be happening is that the level for SGSearch overrides the level set for the root logger somehow. I can't figure it out. I have confirmed that Log4J is reading then properties file I think it is, and no other (via the -Dlog4j.debug option)

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• longest common subsequence

  - by davit-datuashvili

  i have following code public class LCS1 { public static String lcs(String a,String b) { String x; String y; int alen=a.length(); int blen=b.length(); if (alen==0 || blen==0) { return ""; } else if (a.charAt(alen-1)==b.charAt(blen-1)) { return lcs(a.substring(0,alen-1),b.substring(0,blen-1)); } else { x=lcs(a,b.substring(0,blen-1)); y=lcs(a.substring(0,alen-1),b); } return (x.length()>y.length()) ? x : y; } public static void main(String[]args){ String a="computer"; String b="houseboat"; System.out.println(lcs(a,b)); } } it should return "out" but returns nothing what is problem?

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• How can I instruct the Sun JAX-WS Reference Implementation to construct a Web Service SOAP response

  - by Derek Mahar

  Given a Web Service response object for which the Sun JAX-WS Reference Implementation has bindings to generate XML, how can I instruct the Sun JAX-WS RI construct a SOAP message that represents the object? The format of the output message should be identical to that which JAX-WS would generate if it were sending the message as a response to a SOAP request.

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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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• Looking for android Facebook SDK examples...

  - by brybam

  I've looked all over the internet and can't seem to find what i'm looking for... I'm just trying to find a site with some examples on how to use the OFFICIAL facebook android SDK http://github.com/facebook/facebook-android-sdk To be specific i'd like to see some examples on notification use and simple photo upload. But i'll take anything to help get a feel for using the SDK. If anyone knows of any examples please share thank you so much!

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• How to retrieve the ordered list of best articles having a minimum number of votes by using HSQL ?

  - by fabien7474

  I have a Vote domain class from my grails application containing properties like article_id and note I want to HQL query the Vote domain class in order to retrieve the 5 best rated articles having at least 10 votes. I tried : SELECT v.article_id, avg(v.note), count(*) FROM vote v where count(*) >= 10 group by v.article_id order by avg(v.note) desc limit 5; But unfortunately the insertion of where count(*) >= 10 throws an error. How can I do that in a simple way? Thank you for your help.

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• Just need someone familiar with HTTPClient to check over a piece of code

  - by jax

  here are two little helper methods I have made for downloading files. I have had to mix and match different tutorials of the web to get what I have here. Now is there anything that I have done blatantly wrong here? public static InputStream simplePostRequest(URL url, List<NameValuePair> postData) throws ClientProtocolException, IOException { DefaultHttpClient httpclient = new DefaultHttpClient(); HttpPost postMethod=new HttpPost(url.toExternalForm()); postMethod.setEntity(new UrlEncodedFormEntity(postData, HTTP.UTF_8)); HttpResponse response = httpclient.execute(postMethod); HttpEntity entity = response.getEntity(); return entity.getContent(); } public static InputStream simpleGetRequest(URL url, List<NameValuePair> queryString) throws ClientProtocolException, IOException { Uri.Builder uri = new Uri.Builder(); uri.path(url.getPath()); for(NameValuePair nvp: queryString) { uri.appendQueryParameter(nvp.getName(), nvp.getValue()); } DefaultHttpClient httpClient = new DefaultHttpClient(); HttpHost host = new HttpHost(url.getHost()); HttpResponse response = httpClient.execute(host, new HttpGet(uri.build().toString())); HttpEntity entity = response.getEntity(); return entity.getContent(); }

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• Anyone have a good solution for scraping the HTML source of a page with content (in this case, HTML

  - by phpwns

  Anyone have a good solution for scraping the HTML source of a page with content (in this case, HTML tables) generated with Javascript? An embarrassingly simple, though workable solution using Crowbar: <?php function get_html($url) // $url must be urlencode(d) { $context = stream_context_create(array( 'http' => array('timeout' => 120) // HTTP timeout in seconds )); $html = substr(file_get_contents('http://127.0.0.1:10000/?url=' . $url . '&delay=3000&view=browser', 0, $context), 730, -32); // substr removes HTML from the Crowbar web service, returning only the $url HTML return $html; } ?> The advantage to using Crowbar is that the tables will be rendered (and accessible) thanks to the headless mozilla-based browser. The problem, of course, is being dependent on on an external web service, especially given that SIMILE seems to undergo regular server maintenance. :( A pure php solution would be nice, but any functional (and reliable) alternatives would be great.

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• calculate business days including holidays

  - by ran

  i need to calculate the business days between two dates. ex : we have holiday(in USA) on july4th. so if my dates are date1 = 07/03/2012 date2 = 07/06/2012 no of business days b/w these dates should be 1 since july4th is holiday. i have a below method to calclulate the business days which will only counts week ends but not holidays. is there any way to calculate holidays also....please help me on this. public static int getWorkingDaysBetweenTwoDates(Date startDate, Date endDate) { Calendar startCal; Calendar endCal; startCal = Calendar.getInstance(); startCal.setTime(startDate); endCal = Calendar.getInstance(); endCal.setTime(endDate); int workDays = 0; //Return 0 if start and end are the same if (startCal.getTimeInMillis() == endCal.getTimeInMillis()) { return 0; } if (startCal.getTimeInMillis() > endCal.getTimeInMillis()) { startCal.setTime(endDate); endCal.setTime(startDate); } do { startCal.add(Calendar.DAY_OF_MONTH, 1); if (startCal.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY && startCal.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) { ++workDays; } } while (startCal.getTimeInMillis() < endCal.getTimeInMillis()); return workDays; }

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