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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 using the break statement bad practice?

  - by Lchi

  I've been told by professors and peers at my university that using the break statement is bad practice, but through my coursework haven't come up with a great reason why. Those who claim that it is bad say that it's a "get out of jail free card" and that you can always avoid using it. My guesses for why its considered bad would be that you could possibly skip some cleanup code after the break, or similarly exit some control structure in an inconsistent state. Is there any reason why using break is(n't) bad practice?

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• Deploying Multiple Environments in Spring-MVC

  - by jboyd

  Currently all web apps are deployed using seperate config files: <!-- <import bean.... production/> --> <import bean... development/> This has disadvantages, even if you only need to swap out one config file, that I'm sure everyone is familiar with (wondering what just deployed without searching through XML is one of them) I want to add Logging to my application that basically says 'RUNNING IN PRODUCTION MODE', with a description of the services deployed and what mode they are working in. RUNNING IN PRODUCTION MODE Client Service - Production Messaging Service - Local and so on... Is this possible in Spring using a conventional deployment (putting a war on a server)? What other things do people do to manage deployments and software configurations? If not, what other ways could you achieve something similar?

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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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• Hibernate: Querying objects by attributes of inherited classes

  - by MichaelD

  Hi all, I ran into a problem with Hibernate concerning queries on classes which use inheritance. Basically I've the following class hierarchy: @Entity @Table( name = "recording" ) class Recording { ClassA attributeSet; ... } @Entity @Inheritance( strategy = InheritanceType.JOINED ) @Table( name = "classA" ) public class ClassA { String Id; ... } @Entity @Table( name = "ClassB1" ) @PrimaryKeyJoinColumn( name = "Id" ) public class ClassB1 extends ClassA { private Double P1300; private Double P2000; } @Entity @Table( name = "ClassB2" ) @PrimaryKeyJoinColumn( name = "Id" ) public class ClassB2 extends ClassA { private Double P1300; private Double P3000; } The hierarchy is already given like this and I cannot change it easily. As you can see ClassB1 and ClassB2 inherit from ClassA. Both classes contain a set of attributes which sometimes even have the same names (but I can't move them to ClassA since there are possible more sub-classes which do not use them). The Recording class references one instance of one of this classes. Now my question: What I want to do is selecting all Recording objects in my database which refer to an instance of either ClassB1 or ClassB2 with e.g. the field P1300 == 15.5 (so this could be ClassB1 or ClassB2 instances since the P1300 attribute is declared in both classes). What I tried is something like this: Criteria criteria = session.createCriteria(Recording.class); criteria.add( Restrictions.eq( "attributeSet.P1300", new Double(15.5) ) ); criteria.list(); But since P1300 is not an attribute of ClassA hibernate throws an exception telling me: could not resolve property: P1300 of: ClassA How can I tell hibernate that it should search in all subclasses to find the attribute I want to filter? Thanks MichaelD

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• Why aren't arrays expandable?

  - by Mustafa

  When we create an array, we cannot change its size; it's fixed. OK, seems nice, we can create a new bigger array and copy the values one by one and that's little slow. What's the technical background of it?

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• Compute weighted averages for large numbers

  - by Travis

  I'm trying to get the weighted average of a few numbers. Basically I have: Price - 134.42 Quantity - 15236545 There can be as few as one or two or as many as fifty or sixty pairs of prices and quantities. I need to figure out the weighted average of the price. Basically, the weighted average should give very little weight to pairs like Price - 100000000.00 Quantity - 3 and more to the pair above. The formula I currently have is: ((price)(quantity) + (price)(quantity) + ...)/totalQuantity So far I have this done: double optimalPrice = 0; int totalQuantity = 0; double rolling = 0; System.out.println(rolling); Iterator it = orders.entrySet().iterator(); while(it.hasNext()) { System.out.println("inside"); Map.Entry order = (Map.Entry)it.next(); double price = (Double)order.getKey(); int quantity = (Integer)order.getValue(); System.out.println(price + " " + quantity); rolling += price * quantity; totalQuantity += quantity; System.out.println(rolling); } System.out.println(rolling); return totalQuantity / rolling; The problem is I very quickly max out the "rolling" variable. How can I actually get my weighted average? Thanks!

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• Is it valid for Hibernate list() to return duplicates?

  - by skaffman

  Is anyone aware of the validity of Hibernate's Criteria.list() and Query.list() methods returning multiple occurrences of the same entity? Occasionally I find when using the Criteria API, that changing the default fetch strategy in my class mapping definition (from "select" to "join") can sometimes affect how many references to the same entity can appear in the resulting output of list(), and I'm unsure whether to treat this as a bug or not. The javadoc does not define it, it simply says "The list of matched query results." (thanks guys). If this is expected and normal behaviour, then I can de-dup the list myself, that's not a problem, but if it's a bug, then I would prefer to avoid it, rather than de-dup the results and try to ignore it. Anyone got any experience of this?

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• Entities equals(), hashCode() and toString(). How to correctly implement them?

  - by spike07

  I'm implementing equals(), hashCode() and toString() of my entities using all the available fields in the bean. I'm getting some Lazy init Exception on the frontend when I try to compare the equality or when I print the obj state. That's because some list in the entity can be lazy initialized. I'm wondering what's the correct way to for implementing equals() and toString() on an entity object.

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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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• Automatically copy new Jar file to Tomcat project WEB-INF/lib folder

  - by The D Williams

  I am developing a Tomcat app (actually it's a Red5 app, but this is effectively the same). This contains the usual /WebContent/WEB-INF/lib folder, which is where I locate the various jars it uses. Recently, I pulled a package out of my app project, and converted into a separate Jar project which was then released as open source (this resides in the same workspace). What I want, is that when I build my Tomcat app, that Eclipse automatically pulls the latest version of the Jar I have built into its /WebContent/WEB-INF/lib folder. This is the behaviour you get with .NET when you reference one project from another, and I guess this is why I was expecting to find some way of doing it. At the moment, I have to manually copy/paste the Jar across each time I build it. Of course, ideally when I build my Tomcat app it would automatically detect if the Jar project was up-to-date too, and build it if not. Any suggestions most gratefully received.

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• Using Comparable to compare objects and sorting them in a TreeMap

  - by arjacsoh

  II cannot understand how should the natural ordering of class be "consistent with equals" when implementing the Comparable interface. I deteted a flaw in my program and therefore I deteced that in the documentantion of the interface Comparable. My problem is that although two Objects are considered as distinct on the base of equals method, the TreeMap structure treats them as equal and consequently does not accept the second insert. The sample code is: public class Car implements Comparable<Car> { int weight; String name; public Car(int w, String n) { weight=w; name=n; } public boolean equals(Object o){ if(o instanceof Car){ Car d = (Car)o; return ((d.name.equals(name)) && (d.weight==weight)); } return false; } public int hashCode(){ return weight/2 + 17; } public String toString(){ return "I am " +name+ " !!!"; } public int compareTo(Car d){ if(this.weight>d.weight) return 1; else if(this.weight<d.weight) return -1; else return 0; } /*public int compareTo(Car d){ return this.name.compareTo(d.name); }*/ } public static void main(String[] args) { Car d1 = new Car(100, "a"); Car d2 = new Car(110, "b"); Car d3 = new Car(110, "c"); Car d4 = new Car(100, "a"); Map<Car, Integer> m = new HashMap<Car, Integer>(); m.put(d1, 1); m.put(d2, 2); m.put(d3, 3); m.put(d4, 16); for(Map.Entry<Car, Integer> me : m.entrySet()) System.out.println(me.getKey().toString() + " " +me.getValue()); TreeMap<Car, Integer> tm = new TreeMap<Car, Integer>(m); System.out.println("After Sorting: "); for(Map.Entry<Car, Integer> me : tm.entrySet()) System.out.println(me.getKey().toString() + " " +me.getValue()); } The output is : I am a !!! 16 I am c !!! 3 I am b !!! 2 After Sorting: I am a !!! 16 I am c !!! 2 That is, that the object c has replaced (somewhat) object b. If I comment the original equals method and uncomment the second equals method, which compares the objects according name, the output is the expected: I am a !!! 16 I am c !!! 3 I am b !!! 2 After Sorting: I am a !!! 16 I am b !!! 2 I am c !!! 3 Why does it come around in this way and what should I alter in order to insert and sort different objects with some attributes of equal value in a TreeMap?

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• Help in J2ME for creating image and parse it

  - by HAMED

  Can anyone tell me how i can parse a png image into many png images in J2ME??? for examole:I just wnat to have a source image 150*150 pixel and parse it to 10 image with 15*15 pixel. I write an elemantary code that have exeption. This is my code: public class HelloMIDlet extends MIDlet implements CommandListener { private boolean midletPaused = false; private Command exitCommand; private Form form; private StringItem stringItem; Image im , im2; Form form1 = null; public HelloMIDlet() { try { // create source image im = Image.createImage("/image1.JPG"); int height = im.getHeight() ; int width = im.getWidth() ; int x = 0 ; int y = 0 ; while ( y < height ){ while ( x < width ){ // create 15*15 pixel of source image im2 = im.createImage(im, x, y, 15, 15, Sprite.TRANS_NONE) ; x += 15 ; } y += 15 ; x = 0 ; } } catch (IOException ex) { ex.printStackTrace(); } } please help me to make it right....It's emergency! Thanks a lot guys...

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• Why do I get empty request from the Jakarta Commons HttpClient?

  - by polyurethan

  I have a problem with the Jakarta Commons HttpClient. Before my self-written HttpServer gets the real request there is one request which is completely empty. That's the first problem. The second problem is, sometimes the request data ends after the third or fourth line of the http request: POST / HTTP/1.1 User-Agent: Jakarta Commons-HttpClient/3.1 Host: 127.0.0.1:4232 For debugging I am using the Axis TCPMonitor. There every things is fine but the empty request. How I process the stream: StringBuffer requestBuffer = new StringBuffer(); InputStreamReader is = new InputStreamReader(socket.getInputStream(), "UTF-8"); int byteIn = -1; do { byteIn = is.read(); if (byteIn > 0) { requestBuffer.append((char) byteIn); } } while (byteIn != -1 && is.ready()); String requestData = requestBuffer.toString(); How I send the request: client.getParams().setSoTimeout(30000); method = new PostMethod(url.getPath()); method.getParams().setContentCharset("utf-8"); method.setRequestHeader("Content-Type", "application/xml; charset=utf-8"); method.addRequestHeader("Connection", "close"); method.setFollowRedirects(false); byte[] requestXml = getRequestXml(); method.setRequestEntity(new InputStreamRequestEntity(new ByteArrayInputStream(requestXml))); client.executeMethod(method); int statusCode = method.getStatusCode(); Have anyone of you an idea how to solve these problems? Alex

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• JTextField that has inner fields or preformated format, something like the ip field in windows

  - by dimitar

  Hello guys, i want to create a text field that will be for date and will have dd.mm.YYYY format. Now what i want to do is the user to type only the numbers, not the dots to. So the field would be like: _ _. _ _ . _ _ _ _ So when the user wants to type the date: 15.05.2010 for example, he will only type the numbers in the sequence 15052010. Also i would like, when he preses on left or right arrow, the cursor to go from one field(not JTextField, but field in the JTextField). So lets say i have JTextField with text in it: 15.05.2010, so if user is on the beginning and he preses right arrow, the cursor to go to the .05 field. I hope you understand me 'cos right now i don't any idea how to make this, or at least how to look for it on google. Thank you.

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• Get enum by it's inner field

  - by zeroed

  Hi! Have enum with inner fields, kind of map. Now I need to get enum by it's inner field. Wrote this: package test; /** * Test enum to test enum =) */ public enum TestEnum { ONE(1), TWO(2), THREE(3); private int number; TestEnum(int number) { this.number = number; } public TestEnum findByKey(int i) { TestEnum[] testEnums = TestEnum.values(); for (TestEnum testEnum : testEnums) { if (testEnum.number == i) { return testEnum; } } return null; } } But it's not very efficient to look up through all enums each time I need to find appropriate instance. Is there any other way to do the same?

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• How to add a jar build by a project to the project in eclipse?

  - by Xetius

  I have a project which as part of the build process creates an XMLBeans jar file (stbSchemas.jar) which I want to include and reference in this project. Is this the best way to go about this (Single project) or should I have a child project which is built from the parent project? I am building this using Maven2 inside Eclipse. Is there a better way to do this so that I can maintain the integrity of the projects and stability of the builds.

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• Android Content Provider database leak issue

  - by MattC

  I am writing a content provider for this application and in my content provider I am opening a database connection, running a query and returning the cursor of results to the calling program. If I close this database connection in the provider, the cursor has no results. If I leave it open, I get "leak found" errors in my DDMS log. What am I missing here? What's the clean, proper way to return a cursor of database results?

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• Why does a sub-class class of a class have to be static in order to initialize the sub-class in the

  - by Alex

  So, the question is more or less as I wrote. I understand that it's probably not clear at all so I'll give an example. I have class Tree and in it there is the class Node, and the empty constructor of Tree is written: public class RBTree { private RBNode head; public RBTree(RBNode head,RBTree leftT,RBTree rightT){ this.head=head; this.head.leftT.head.father = head; this.head.rightT.head.father = head; } public RBTree(RBNode head){ this(head,new RBTree(),new RBTree()); } public RBTree(){ this(new RBNode(),null,null); } public class RBNode{ private int value; private boolean isBlack; private RBNode father; private RBTree leftT; private RBTree rightT; } } Eclipse gives me the error: "No enclosing instance of type RBTree is available due to some intermediate constructor invocation" for the "new RBTree()" in the empty constructor. However, if I change the RBNode to be a static class, there is no problem. So why is it working when the class is static. BTW, I found an easy solution for the cunstructor: public RBTree(){ this.head = new RBNode(); } So, I have no idea what is the problem in the first piece of code.

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• How do we achieve "substring-match" under O(n) time?

  - by Pacerier

  I have an assignment that requires reading a huge file of random inputs, for example: Adana Izmir Adnan Menderes Apt Addis Ababa Aden ADIYAMAN ALDAN Amman Marka Intl Airport Adak Island Adelaide Airport ANURADHAPURA Kodiak Apt DALLAS/ADDISON Ardabil ANDREWS AFB etc.. If I specify a search term, the program is supposed to find the lines whereby a substring occurs. For example, if the search term is "uradha", the program is supposed to show ANURADHAPURA. If the search term is "airport", the program is supposed to show Amman Marka Intl Airport, Adelaide Airport A quote from the assignment specs: "You are to program this application taking efficiency into account as though large amounts of data and processing is involved.." I could easily achieve this functionality using a loop but the performance would be O(n). I was thinking of using a trie but it seems to only work if the substring starts from index 0. I was wondering what solutions are there which gives a performance better than O(n)?

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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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• How to reverse a string?

  - by WM

  Example : hi how are you; output : you are how hi; but wrote this code and im stuck not knowing how to put a string into an array and reverse it..? public class Reverse { public static void main(String[] args) { Scanner text = new Scanner(System.in); System.out.print("Enter your Text : "); String input = text.nextLine(); Scanner text2 = new Scanner(text.nextLine()); String[] array = new String[] ; int i; for(i = 0; i < input.length(); i++) { array[i] = input;

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• Round a double to 2 significant figures after decimal point

  - by Rajesh

  suppose if the value is 200.3456 it should be formatted to 200.34 or if it is 200 then it should be 200.00

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• How to use LocalValueBean in jsp page.

  - by Himanshu

  I have set certain bean label and bean value in one of my dao class.. I have created a list of LocalValueBean objects and passed it as a list to jsp.. now here at jsp i need to print the label seperately and on hover to the label i need to show the value.. i need to exttract or to say get those values in jsp directly... i have also imported the org.apache.struts.util.LabelValueBean in my jsp but still its not working.. please let me know if you any ideas...

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• JSF: Avoid nested update calls

  - by dhroove

  I don't know if I am on right track or not still asking this question. I my JSF project I have this tree structure: <p:tree id="resourcesTree" value="#{someBean.root}" var="node" selectionMode="single" styleClass="no-border" selection="#{someBean.selectedNode}" dynamic="true"> <p:ajax listener="#{someBean.onNodeSelect}" update=":centerPanel :tableForm :tabForm" event="select" onstart="statusDialog.show();" oncomplete="statusDialog.hide();" /> <p:treeNode id="resourcesTreeNode" > <h:outputText value="#{node}" id="lblNode" /> </p:treeNode> </p:tree> I have to update this tree after I added something or delete something.. But whenever I update this still its nested update also call I mean to say it also call to update these components ":centerPanel :tableForm :tabForm"... This give me error that :tableForm not found in view because this forms load in my central panel and this tree is in my right panel.. So when I am doing some operation on tree is it not always that :tableForm is in my central panel.. (I mean design is something like this only) So now my question is that can I put some condition or there is any way so that I can specify when to update nested components also and when not.... In nut shell is there any way to update only :resoucesTree is such a way that nested updates are not called so that I can avoid error... Thanks in advance.

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