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  • Properly removing an Integer from a List<Integer>

    - by Yuval A
    Here's a nice pitfall I just encountered. Consider a list of integers: List<Integer> list = new ArrayList<Integer>(); list.add(5); list.add(6); list.add(7); list.add(1); Any educated guess on what happens when you execute list.remove(1)? What about list.remove(new Integer(1))? This can cause some nasty bugs. What is the proper way to differentiate between remove(int index), which removes an element from given index and remove(Object o), which removes an element by reference, when dealing with lists of integers? The main point to consider here is the one @Nikita mentioned - exact parameter matching takes precedence over auto-boxing.

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  • Can I connect to SQL from JavaScript MVC?

    - by user54197
    I am populating a list of names that will be added to my Sql Database. In this simple case, how do I send the information to SQL server without my page being refreshed? <script type="text/javascript"> function addNewRow() { $('#displayPropertyTable tr:last').after('<tr><td style="font-size:smaller;" class="name"></td><td style="font-size:smaller;" class="address"></td></tr>'); var $tr = $('#displayPropertyTable tr:last'); var propertyCondition = $('#txtPropAddress').val(); if (propertyCondition != "") { $tr.find('.name').text($('#txtPropName').val()); $tr.find('.address').text($('#txtPropAddress').val()); } } </script> ... <table id="displayPropertyTable" width= "100%"> <tr> <td style="font-size:smaller;" class="name"></td> <td style="font-size:smaller;" class="address"></td> </tr> </table> ... <table> <tr> <td><b>Name</b></td> <td colspan="2"><input id="txtPropName" type="text" /></td> </tr> <tr> <td><b>Address</b></td> <td colspan="2"><input id="txtPropAddress" type="text" /></td> </tr> </table> ... <button onclick="addNewRow();">Add</button>

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  • Designing a class in such a way that it doesn't become a "God object"

    - by devoured elysium
    I'm designing an application that will allow me to draw some functions on a graphic. Each function will be drawn from a set of points that I will pass to this graphic class. There are different kinds of points, all inheriting from a MyPoint class. For some kind of points it will be just printing them on the screen as they are, others can be ignored, others added, so there is some kind of logic associated to them that can get complex. How to actually draw the graphic is not the main issue here. What bothers me is how to make the code logic such that this GraphicMaker class doesn't become the so called God-Object. It would be easy to make something like this: class GraphicMaker { ArrayList<Point> points = new ArrayList<Point>(); public void AddPoint(Point point) { points.add(point); } public void DoDrawing() { foreach (Point point in points) { if (point is PointA) { //some logic here else if (point is PointXYZ) { //...etc } } } } How would you do something like this? I have a feeling the correct way would be to put the drawing logic on each Point object (so each child class from Point would know how to draw itself) but two problems arise: There will be kinds of points that need to know all the other points that exist in the GraphicObject class to know how to draw themselves. I can make a lot of the methods/properties from the Graphic class public, so that all the points have a reference to the Graphic class and can make all their logic as they want, but isn't that a big price to pay for not wanting to have a God class?

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  • What can cause my code to run slower when the server JIT is activated?

    - by durandai
    I am doing some optimizations on an MPEG decoder. To ensure my optimizations aren't breaking anything I have a test suite that benchmarks the entire codebase (both optimized and original) as well as verifying that they both produce identical results (basically just feeding a couple of different streams through the decoder and crc32 the outputs). When using the "-server" option with the Sun 1.6.0_18, the test suite runs about 12% slower on the optimized version after warmup (in comparison to the default "-client" setting), while the original codebase gains a good boost running about twice as fast as in client mode. While at first this seemed to be simply a warmup issue to me, I added a loop to repeat the entire test suite multiple times. Then execution times become constant for each pass starting at the 3rd iteration of the test, still the optimized version stays 12% slower than in the client mode. I am also pretty sure its not a garbage collection issue, since the code involves absolutely no object allocations after startup. The code consists mainly of some bit manipulation operations (stream decoding) and lots of basic floating math (generating PCM audio). The only JDK classes involved are ByteArrayInputStream (feeds the stream to the test and excluding disk IO from the tests) and CRC32 (to verify the result). I also observed the same behaviour with Sun JDK 1.7.0_b98 (only that ist 15% instead of 12% there). Oh, and the tests were all done on the same machine (single core) with no other applications running (WinXP). While there is some inevitable variation on the measured execution times (using System.nanoTime btw), the variation between different test runs with the same settings never exceeded 2%, usually less than 1% (after warmup), so I conclude the effect is real and not purely induced by the measuring mechanism/machine. Are there any known coding patterns that perform worse on the server JIT? Failing that, what options are available to "peek" under the hood and observe what the JIT is doing there?

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  • Is it bad to have multiple return statements?

    - by scot
    Hi, I have a code somethg like below: int method(string a ,int b , int c){ if(cond1) return -1; if(cond2 || cond3) return 3; if(cond1 && cond2) return 0; else return -999; } Does it perform badly when compared to having multiple if else and have single return?

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  • When to use LinkedList<> over ArrayList<>?

    - by sdellysse
    I've always been one to simply use List<String> names = new ArrayList<String>(); I use the interface as the type name for portability, so that when I ask questions such as these I can rework my code. When should LinkedList should be used over ArrayList and vice-versa?

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  • Meta Search Engine Architecture

    - by Loki
    The question wasn't clear enough, I think; here's an updated straight to the point question: What are the common architectures used in building a meta search engine and is there any libraries available to build that type of search engine? I'm looking at building an "enterprise" type of search engine where the indexed data could be coming from proprietary (like Autonomy or a Google Box) or public search engines (like Google Web or Yahoo Web).

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  • Workaround for richfaces combobox hotkey bug

    - by John
    Hi, Does anyone know a workaround for the bug https://jira.jboss.org/jira/browse/RF-8076 ? Just to clarify things, we have a form with multiple inputs, one of them being a combobox with auto complete features. We've setup a hotkey via <rich:hotKey key="return" ... /> It works great everywhere except in the combobox, and I would really like to get it working on the combobox as well. The behaviour I want when the ENTER key is pressed inside the combobox is: If the combobox context was modified by auto complete then do nothing Else action the event on ENTER key pressed We're running on seam/richfaces. I'm open to any workaround, but simplicity is much sought for. Thanks!

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  • How to perform a non-polymorphic HQL query in Hibernate?

    - by Eli Acherkan
    Hi all, I'm using Hibernate 3.1.1, and in particular, I'm using HQL queries. According to the documentation, Hibernate's queries are polymorphic: A query like: from Cat as cat returns instances not only of Cat, but also of subclasses like DomesticCat. How can I query for instances of Cat, but not of any of its subclasses? I'd like to be able to do it without having to explicitly mention each subclass. I'm aware of the following options, and don't find them satisfactory: Manually filtering the instances after the query, OR: Manually adding a WHERE clause on the discriminator column. It would make sense for Hibernate to allow the user to decide whether a query should be polymorphic or not, but I can't find such an option. Thanks in advance!

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  • How to get path to wallpaper

    - by kentcdodds
    My Question: How do you get the filepath to the current wallpaper? Expansion: I'm writing an app that will let you change the wallpaper easily between different presets. I want to store the filepath of the available wallpapers in my database. What I've tried: WallpaperManger.getWallpaperInfo() or WallpaperManger.getDrawable(). Neither seem to contain the actual location of the file. Any help would be appreciated! :D Thanks! Also, I'm including live-wallpapers. Thanks!

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  • KeyStore, HttpClient, and HTTPS: Can someone explain this code to me?

    - by stormin986
    I'm trying to understand what's going on in this code. KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType()); FileInputStream instream = new FileInputStream(new File("my.keystore")); try { trustStore.load(instream, "nopassword".toCharArray()); } finally { instream.close(); } SSLSocketFactory socketFactory = new SSLSocketFactory(trustStore); Scheme sch = new Scheme("https", socketFactory, 443); httpclient.getConnectionManager().getSchemeRegistry().register(sch); My Questions: trustStore.load(instream, "nopassword".toCharArray()); is doing what exactly? From reading the documentation load() will load KeyStore data from an input stream (which is just an empty file we just created), using some arbitrary "nopassword". Why not just load it with null as the InputStream parameter and an empty string as the password field? And then what is happening when this empty KeyStore is being passed to the SSLSocketFactory constructor? What's the result of such an operation? Or -- is this simply an example where in a real application you would have to actually put a reference to an existing keystore file / password?

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  • Ubuntu terminal questions

    - by Camran
    I am wondering about my VPS providers ubuntu terminal. Are all these terminals the same? I think they are so user-UN-friendly. I can't copy-paste into the terminal, when I try opening textfiles, I can't scroll up and down easily. I cant save easily. Nothing is easy... Is it always like this with Ubuntu? Is there any way to make it easier? I use windows but I login to my vps provider with login details and then simply click "terminal" to open the terminal. Please help me out here

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  • Documenting logic in javadoc

    - by smayers81
    I have a question about where to document logic in javadocs. For example, I have the following method signature in an interface: public int getTotalAssociationsAsParent(Long id, Long type); The method returns associations where the given ID is the parent and the association is of type 'type'. ID is required, but if type passed in is NULL, then I will return ALL associations where the ID is the parent. My question is where should this type of logic be documented? I hesitate putting it in the javadoc of the interface because that sort of constrains all implementing classes to adhere to that logic. Maybe in the future, I'll have an Impl class that throws an IllegalArgumentException if type is NULL. However, if I put it in non-javadoc in the Impl class, then consumers of this method won't know how the method behaves with a NULL type.

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  • Does Hibernate always need a setter when there is a getter?

    - by Marcus
    We have some Hibernate getter methods annotated with both @Column and @Basic. We get an exception if we don't have the corresponding setter. Why is this? In our case we are deriving the value returned from the getter (to get stored in the DB) and the setter has no functional purpose. So we just have an empty method to get around the error condition..

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  • Overriding or overloading?

    - by atch
    Guys I know this question is silly but just to make sure: Having in my class method: boolean equal(Document d) { //do something } I'm overloading this method nor overriding right? I know that this or similiar question will be on upcoming egzam and would be stupid to not get points for such a simple mistake;

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  • How can I make a family of singletons?

    - by Jay
    I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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  • Remove stateful EJB bean in client

    - by palto
    I'm currently learning EJB and as I understand when client gets a stateful session bean the server keeps it in memory(or passivates it) until the client removes the bean. Pretty simple, except nowhere I have seen any examples of how the client can actually remove the bean. How do you do that other than shutting down your client application? Or do I just have to implement a reset method in all my stateful beans if I want to start over?

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  • Are memcached entries saved by the Danga client compatible with the Spy client?

    - by jigjig
    After saving a String value into memcached using the Danga client, I attempted to get the entry using the Spy client. The two String values are not the same. The Danga client retrieves a string with an additional empty char prepended to the string, therefore violating the equality condition. Danga: t,e,s,t,s,t,r,i,n,g Spy: ,t,e,s,t,s,t,r,i,n,g I also attempted to save a serialized Map using the Danga client and get the Map using the Spy client. The Spy client is able to only get a String form of the Map. The string contains binary values, as below: sr

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  • jaxb entity print out as xml

    - by Cristian Boariu
    Hi, I have a class, let's say User adnotated with @XmlRootElement, with some properties (name, surname etc). I use this class for REST operations, as application/xml. The client will POST User class so i want to keep the values in the log. Is there any method in jax-ws to prints out this object as xml? For instance: log.info("Customers sent a USER"+user.whichMethod()); Customer sent a User <user> <name>cristi</name> <surname>kevin</surname> </user> Thanks.

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  • HibernateFilter.doFilter ServletException?

    - by Austin R
    I have pretty much zero experience setting up servers, but currently my job is to set one up (don't ask why). It's an an apache-tomcat6 server. I followed some instructions step by step, and when it came time to test that everything was working, here's what I got: I know this is a bit of a shot in the dark, but does anyone know what I can do to fix this? Please let me know if there's any further information I can provide to help!

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