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  • Benefits of arrays

    - by Vitalii Fedorenko
    As I see it, the advantages of List over array are pretty obvious: Generics provide more precise typing: List<Integer>, List<? extends Number>, List<? super Integer>. List interface has a bunch useful methods: addAll, remove etc. While for arrays all standard operations except get/set must be performed in a procedure manner by passing it to a static method. Collections offer different implementations like ArrayList, LinkedList, unmodifieable and synchronized lists, which can be hidden under common List interface. OOB length control. As disadvantages I can only mention absence of syntactic sugar and runtime type check. At the same time supporting of both structures requires frequent using of asList and toArray methods, which makes code less readable. So I am curious if there are any important benefits of using arrays that I miss.

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  • Trying to setup externalizing properties in spring

    - by Gandalf StormCrow
    Hi all, I'm building my project with maven so according to maven way, config should be in src/main/conf , how can I say to my spring application context that that is where jdbc.properties is found? Here is example bean : <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location" value="jdbc.properties" /> </bean> Spring assumens that this configuration is inside src/main/webapp/WEB-INF, I hope I've been clear if not I'll rephrase my question thank you

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  • Get a value from hashtable by a part of its key

    - by htf
    Hi. Say I have a Hashtable<String, Object> with such keys and values: apple => 1 orange => 2 mossberg => 3 I can use the standard get method to get 1 by "apple", but what I want is getting the same value (or a list of values) by a part of the key, for example "ppl". Of course it may yield several results, in this case I want to be able to process each key-value pair. So basically similar to the LIKE '%ppl%' SQL statement, but I don't want to use a (in-memory) database just because I don't want to add unnecessary complexity. What would you recommend?

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  • Should I use a modified singleton design pattern that only allows one reference to its instance?

    - by Graham
    Hi, I have a class that would normally just generate factory objects, however this class should only used once throughout the program in once specifix place. What is the best design pattern to use in this instance? I throught that having a modified singleton design which only allows one reference to instance throughout the program would be the correct way to go. So only the first call to getInstance() returns the factory library. Is this a good or bad idea? Have I missed out another fundermental design pattern for solving this problem? Thanks for your help.

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  • How can i make projects bound to eachother in eclipse?

    - by ikky
    Hi! I have 3 projects in Eclipse that are bound to eachother. With bound i mean this: Everytime i add a class in one of the projects, the other projects also updates themselves and add the class Now i want to add another project to these, but i don't know how to bind it together with the other projects. Any suggestions? Thanks in advance!

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  • Thread sleep and thread join.

    - by Dhruv Gairola
    hi guys, if i put a thread to sleep in a loop, netbeans gives me a caution saying Invoking Thread.sleep in loop can cause performance problems. However, if i were to replace the sleep with join, no such caution is given. Both versions compile and work fine tho. My code is below (check the last few lines for "Thread.sleep() vs t.join()"). public class Test{ //Display a message, preceded by the name of the current thread static void threadMessage(String message) { String threadName = Thread.currentThread().getName(); System.out.format("%s: %s%n", threadName, message); } private static class MessageLoop implements Runnable { public void run() { String importantInfo[] = { "Mares eat oats", "Does eat oats", "Little lambs eat ivy", "A kid will eat ivy too" }; try { for (int i = 0; i < importantInfo.length; i++) { //Pause for 4 seconds Thread.sleep(4000); //Print a message threadMessage(importantInfo[i]); } } catch (InterruptedException e) { threadMessage("I wasn't done!"); } } } public static void main(String args[]) throws InterruptedException { //Delay, in milliseconds before we interrupt MessageLoop //thread (default one hour). long patience = 1000 * 60 * 60; //If command line argument present, gives patience in seconds. if (args.length > 0) { try { patience = Long.parseLong(args[0]) * 1000; } catch (NumberFormatException e) { System.err.println("Argument must be an integer."); System.exit(1); } } threadMessage("Starting MessageLoop thread"); long startTime = System.currentTimeMillis(); Thread t = new Thread(new MessageLoop()); t.start(); threadMessage("Waiting for MessageLoop thread to finish"); //loop until MessageLoop thread exits while (t.isAlive()) { threadMessage("Still waiting..."); //Wait maximum of 1 second for MessageLoop thread to //finish. /*******LOOK HERE**********************/ Thread.sleep(1000);//issues caution unlike t.join(1000) /**************************************/ if (((System.currentTimeMillis() - startTime) > patience) && t.isAlive()) { threadMessage("Tired of waiting!"); t.interrupt(); //Shouldn't be long now -- wait indefinitely t.join(); } } threadMessage("Finally!"); } } As i understand it, join waits for the other thread to complete, but in this case, arent both sleep and join doing the same thing? Then why does netbeans throw the caution?

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  • In ArrayBlockingQueue, why copy final member field into local final variable?

    - by mjlee
    In ArrayBlockingQueue, any method that requires lock will get set 'final' local variable before calling 'lock()'. public boolean offer(E e) { if (e == null) throw new NullPointerException(); final ReentrantLock lock = this.lock; lock.lock(); try { if (count == items.length) return false; else { insert(e); return true; } } finally { lock.unlock(); } } Is there any reason to set a local variable 'lock' from 'this.lock' when field 'this.lock' is final also. Additionally, it also set local variable of E[] before acting on. private E extract() { final E[] items = this.items; E x = items[takeIndex]; items[takeIndex] = null; takeIndex = inc(takeIndex); --count; notFull.signal(); return x; } Is there any reason for copying to local final variable?

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  • How can I make CAPTCHA work across multiple pages?

    - by jm04469
    Ever visit a website such as myspace where they leverage CAPTCHA to prevent spam? The typical pattern is to present a challenge to each URL that is opened, yet the challenge doesn't actually belong to the page itself which causes additional bandwidth usage. So, if I open up six pages at the same time and want to present a challenge on each page. I want the challenge to be tied to the page and not to the session. How can I make this work with Spring and/or Struts.

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  • When to use @Singleton in a Jersey resource

    - by dexter
    I have a Jersey resource that access the database. Basically it opens a database connection in the initialization of the resource. Performs queries on the resource's methods. I have observed that when I do not use @Singleton, the database is being open at each request. And we know opening a connection is really expensive right? So my question is, should I specify that the resource be singleton or is it really better to keep it at per request especially when the resource is connecting to the database? My resource code looks like this: //Use @Singleton here or not? @Path(/myservice/) public class MyResource { private ResponseGenerator responser; private Log logger = LogFactory.getLog(MyResource.class); public MyResource() { responser = new ResponseGenerator(); } @GET @Path("/clients") public String getClients() { logger.info("GETTING LIST OF CLIENTS"); return responser.returnClients(); } ... // some more methods ... } And I connect to the database using a code similar to this: public class ResponseGenerator { private Connection conn; private PreparedStatement prepStmt; private ResultSet rs; public ResponseGenerator(){ Class.forName("org.h2.Driver"); conn = DriverManager.getConnection("jdbc:h2:testdb"); } public String returnClients(){ String result; try{ prepStmt = conn.prepareStatement("SELECT * FROM hosts"); rs = prepStmt.executeQuery(); ... //do some processing here ... } catch (SQLException se){ logger.warn("Some message"); } finally { rs.close(); prepStmt.close(); // should I also close the connection here (in every method) if I stick to per request // and add getting of connection at the start of every method // conn.close(); } return result } ... // some more methods ... } Some comments on best practices for the code will also be helpful.

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  • Use of private constructor to prevent instantiation of class?

    - by cringe
    Hi guys! Right now I'm thinking about adding a private constructor to a class that only holds some String constants. public class MyStrings { // I want to add this: private MyString() {} public static final String ONE = "something"; public static final String TWO = "another"; ... } Is there any performance or memory overhead if I add a private constructor to this class to prevent someone to instantiate it? Do you think it's necessary at all or that private constructors for this purpose are a waste of time and code clutter?

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  • find substrings inside string

    - by senzacionale
    How can i find substrings inside string and then remember and delete it when i found it. EXAMPLE: select * from (select a.iid_organizacijske_enote, a.sifra_organizacijske_enote "Sifra OE", a.naziv_organizacijske_enote "Naziv OE", a.tip_organizacijske_enote "Tip OE" I would like to get all word inside " ", so Sifra OE Naziv OE TIP OE and return select * from (select a.iid_organizacijske_enote, a.sifra_organizacijske_enote, a.naziv_organizacijske_enote, a.tip_organizacijske_enote i try with regex, indexOf() but no one works ok

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  • Spring MVC JSP Parameters

    - by zpinter
    I'm looking to turn off try blocks for a specific JSP page (though turning it off globally would be OK as well). From what I've gathered, it looks something like this: <jsp-param> <param-name>noTryBlocks</param-name> <param-value>true</param-value> </jsp-param> However, everywhere I see that sample it's for a weblogic.xml file. Does anybody know how I can set this JSP parameters for a Spring MVC application? web.xml? Perhaps somewhere near here?: <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/> <property name="prefix" value="/WEB-INF/jsp/"/> <property name="suffix" value=".jsp"/> </bean>

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  • What is the most efficient way to list all of the files in a directory (including sub-directories)?

    - by prometheus
    I am writing a servlet which will examine a directory on the server (external to the web container), and recursively search for certain files (by certain files, I mean files that are of a certain extension as well as a certain naming convention). Once these files are found, the servlet responds with a long list of all of the found files (including the full path to the files). My problem is that there are so many files and directories that my servlet goes extremely slow. I was wondering if there was a best practice or existing servlet for this type of problem? Would it be more efficient to simply compile the entire list of files and do the filtering via js/jquery on the client side?

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  • Page Refresh problem

    - by Abhi
    I have a jsp in which there are certain buttons when i am clicking on one of those, the page is refreshing but the problem is that I want to show that section of jsp where the button is on which the user has done the on click event...but the section which is coming is the top of the page but I don't want that. Please provide me with a solution to rectify the situation.

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  • Openid for google apps domain

    - by user268515
    Hi I'm new to openId concepts. I want to use my google apps domain's user-name & password in third party websites for that i followed this link http://jeremiahlee.com/blog/2009/09/28/how-to-setup-openid-with-google-apps/. But i got struck on second step i dont know where and how to create openId file in server.Please Help on this issue it will be very useful for me. Thanks, Sharun.

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  • Refining Solr searches, getting exact matches?

    - by thebluefox
    Afternoon chaps, Right, I'm constructing a fairly complex (to me anyway) search system for a website using Solr, although this question is quite simple I think... I have two search criteria, location and type. I want to return results that are exact matches to type (letter to letter, no exceptions), and like location. My current search query is as follows ../select/?q=location:N1 type:blue&rows=100&fl=*,score&debugQuery=true This firstly returns all the type blue's that match N1, but then returns any type that matches N1, which is opposite to what I'm after. Both fields are set as textgen in the Solr schema. Any pointers? Cheers gang

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  • Implementing clone on a LinkedList

    - by devoured elysium
    I am trying to implement a clone() method on a DoubleLinkedList. Now, the problem is that implementing it by "the convention" is a lot more troublesome than just creating a new DoubleLinkedList and filling it with all the elements of my current DoubleLinkedList. Is there any inconvenient I am not seeing when doing that? Here is my current approach: @Override public DoubleLinkedList<T> clone() { DoubleLinkedList<T> dll = new DoubleLinkedList<T>(); for (T element : dll) { dll.add(element); } return dll; } Here is what it would be by the convention: @Override public DoubleLinkedList<T> clone() { try { DoubleLinkedList<T> dll = (DoubleLinkedList<T>)super.clone(); //kinda complex code to copy elements return dll; } catch (CloneNotSupportedException e) { throw new InternalError(e.toString()); } }

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  • Is this a correct iText design?

    - by Lucas
    I´m making some pdf reports to be used on a web app. I wonder if the way I´m taking to make the designs is appropriated. This would be a screenshot of the way I´m doing the things. As you can see, I´m using tables to position everything in the document. I think this is a pretty much similar design to HTML. But I want to know is there is a better way to get the same result I got. This is the document without cell borders: I could post the code if necessary. By the way, why should I spend long hours programming these kind of stuff with iText tool when I could do things faster and maybe better looking with iReport? I like iText, it´s just a question. Sorry for my english and thanks!

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  • how should i load a bitmap for an android game?

    - by Heysus Escobar
    i been working on a game with no bitmaps or anything, I'm using rectangles as objects and changing their color for their purpose like a red rectangles for player and gray rectangles for walls. My question is what is the right way to replace the rectangles with bitmaps/images? I know to load Bitmaps you can just do this : Bitmap randomBitmap = BitmapFactory.decodeResource(getResources(), com.example.android4gametest.R.drawable.ic_launcher); Should i load all my Bitmaps and pass them to their Classes or should i load the bitmap inside their class instead of passing it ? and how would i do that because i cannot use the BitmapFactory because i have no access to the getResources()! or should i load my bitmaps/images from my assets folder which i know i wont have the same "tools" you can say to mess with the bitmap.

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  • Tuning garbage collections for low latency

    - by elec
    I'm looking for arguments as to how best to size the young generation (with respect to the old generation) in an environment where low latency is critical. My own testing tends to show that latency is lowest when the young generation is fairly large (eg. -XX:NewRatio <3), however I cannot reconcile this with the intuition that the larger the young generation the more time it should take to garbage collect. The application runs on linux, jdk 6 before update 14, i.e G1 not available.

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  • JMenu issue with Gnome's native look and feel.

    - by gmunk
    I stumbled on a very odd problem while trying to set up a JMenuBar with the native look and feel of Gnome. Here is a screenshot: http://img23.imageshack.us/i/issuel.png/ It has to say File there but it gets cut out. http://pastebin.com/CjFhmxcf http://pastebin.com/gwB3vnC3 Any, help is appreciated!

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