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  • Find messages from certain key till certain key while being able to remove stale keys.

    - by Alfred
    My problem Let's say I add messages to some sort of datastructure: 1. "dude" 2. "where" 3. "is" 4. "my" 5. "car" Asking for messages from index[4,5] should return: "my","car". Next let's assume that after a while I would like to purge old messages because they aren't useful anymore and I want to save memory. Let's say at time x messages[1-3] became stale. I assume that it would be most efficient to just do the deletion once every x seconds. Next my datastructure should contain: 4. "my" 5. "car" My solution? I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the old messages from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement(efficiently/thread-safe) this or maybe use a library?

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  • Design issue when having classes implement different interfaces to restrict client actions

    - by devoured elysium
    Let's say I'm defining a game class that implements two different views: interface IPlayerView { void play(); } interface IDealerView { void deal(); } The view that a game sees when playing the game, and a view that the dealer sees when dealing the game (this is, a player can't make dealer actions and a dealer can't make player actions). The game definition is as following: class Game : IPlayerView, IDealerView { void play() { ... } void deal() { ... } } Now assume I want to make it possible for the players to play the game, but not to deal it. My original idea was that instead of having public Game GetGame() { ... } I'd have something like public IPlayerView GetGame() { ... } But after some tests I realized that if I later try this code, it works: IDealerView dealerView = (IDealerView)GameClass.GetGame(); this works as lets the user act as the dealer. Am I worrying to much? How do you usually deal with this patterns? I could instead make two different classes, maybe a "main" class, the dealer class, that would act as factory of player classes. That way I could control exactly what I would like to pass on the the public. On the other hand, that turns everything a bit more complex than with this original design. Thanks

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  • Is it possible to use maven only for running selenium plugin?

    - by tputkonen
    Our pom.xml currently contains both the build settings, as well as execution of selenium using selenium-maven-plugin. I would like to split it in to two pom files, one for the build and unit tests and the second one for executing selenium tests. (This way I could first build the project in Hudson, and after successful build execute Selenium tests using another project). Is it possible to configure maven to only execute the selenium-maven-plugin?

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  • How do you search through a map?

    - by Jack Null
    I have a map: Map<String, String> ht = new HashMap(); and I would like to know how to search through it and find anything matching a particular string. And if it is a match store it into an arraylist. The map contains strings like this: 1,2,3,4,5,5,5 and the matching string would be 5. So for I have this: String match = "5"; ArrayList<String> result = new ArrayList<String>(); Enumeration num= ht.keys(); while (num.hasMoreElements()) { String number = (String) num.nextElement(); if(number.equals(match)) { result.add(number); } }

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  • JDOQL Any way to avoid multiple .contains() calls in the query when searching for the presence of on

    - by Finbarr
    The question pretty much says it all. If I have a class Class A public class A { ... private List<String> keys; ... } And I want to select all A instances from the DataStore that have atleast one of a List of keys, is there a better way of doing it than this: query = pm.newQuery(A.class); query.setFilter("keys.contains(:key1) || keys.contains(:key2) || keys.contains(:key3)"); List<A> results = (List<A>)query.execute(key1, key2, key3); This has not yet been implemented, so I am open to radical suggestions.

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  • How to know any request type with comet in tomcat 6

    - by Alvin
    Hi, I want to create a chat application in Tomcat 6.0, but before allowing any user for chatting I want to authenticate a user or registering its account to the database by passing request to the servlets at the comet Event type Begin. But I don't know how to know about the request type. How can I know a user has already been logged in, or he is making a request for registering his account. How can I know this by implementing CometProcessor interface? Is there any better way to do that task?

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  • Invisible JFrame/JTable how much faster ?

    - by chacko
    I have a swing app. with a jframe with lots of internal frames containing large JTable. Those jtables get updated continuously so there is lots of repainting going on. in some circumstances I can simply keep the JFrame invisible. (frame.setVisible(false)) I was wondering if anybody knows if I will gain something in terms of performance (something considerable or not) such as 50% gain or you would only get 2% gain... and maybe some sort of explaination on what to expect. thanks

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  • How to find out efficiently the auto-generated id for a new object when using JPA?

    - by webstarg
    Hello, I have an attribute which is annotated with @Id. The ID is going to be generated automatically when persisting the object. That means that the ID-value is not defined before I persist the object. After persisting it, it has an ID (in the database), but unfortunately the field still remains null as long as I don't reload it from the DB. is there any easy way to find out the generated id? Or better: To configure that it will be written into the field? Thanks in advance

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  • How to build SVN/Git like Diff in WebApp?

    - by 01
    I have XMLs(or Objects) that represents data at some point in a business process. I would like to be able to see what has changed between step1 and step5(two versions of the same XML or Object). Id like to implement this like diff function in version control system. how to do it in web app? P.S. I dont want to just store those files in VCS and than make it do the diff. However if I could somehow emulate VCS without having one that would be cool. P.S. I know there are some JS frameworks that offer diff functionality, but the XML could have 10MB, so I think it should be dont at server side.

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  • How can I use one stream and save result to many places?

    - by plasticrabbit
    I using servlet and Apache ServletFileUpload that provides stream to uploaded image. All I want to do is to store that image to db and also store resized (I using JAI) version to db. How can I achieve this without saving image to drive. As I understand stream can be read only once. So I need to store whole image in memory? Is it expensive for performance? Or there are another way?

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  • Compute hex color code for an arbitrary string

    - by user222164
    Heading Is there a way to map an arbitrary string to a HEX COLOR code. I tried to compute the HEX number for string using string hashcode. Now I need to convert this hex number to six digits which are in HEX color code range. Any suggestions ? String [] programs = {"XYZ", "TEST1", "TEST2", "TEST3", "SDFSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS"}; for(int i = 0; i < programs.length; i++) { System.out.println( programs[i] + " -- " + Integer.toHexString(programs[i].hashCode())); }

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  • can I get .class from generic type argument?

    - by Mike S
    I have the following class: public abstract class MyClass<T extends Object> { protected T createNewFromData(Reader reader){ GSON.fromJSON(reader,T.class); // T.class isn't allowed :( } } How do I pass a Class<T instance into there? Is there some wierd and wacky work around? Is there a way to get a Class<T reference other than from a pre-instantiated Object of type T? It won't let me do this either: T t = new T(); Class<T> klass = t.class; ANSWER BELOW Thanks to the accepted answer, here is the solution: Type type = new TypeToken<T>(){}.getType(); return gson.fromJson(reader, type);

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  • Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

    - by kpdvx
    An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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  • WHY HAVE YOU ROMOVED MY POST? [closed]

    - by Eddy Freeman
    I posted a question about how to rotate a tile in BufferedImage. I did it in the morning and you removed it. Why have you removed it again? What is wrong with the posts? Tell me before i become angry. You have removed the post twice without informing/telling me the problem. with the posts What is wrong? Tell me. Reply to this post and tell me what is wrong.

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  • jre1.6.0_27 HashMap values() sourcecode

    - by Liu guanghua
    Today, I opened jre1.6.0_27 HashMap values() method sourcecode 389 public Set<K> keySet() 390 { 391 Set localSet = this.keySet; 392 return (this.keySet = new KeySet(null)); 393 } 394 395 public Collection<V> values() 396 { 397 Collection localCollection = this.values; 398 return (this.values = new Values(null)); 399 } I think these sourcecode are error, but I don't know why they look like this. Who can tell me why?

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  • why isn't the input text file being read into the ArrayList<String>, diary?

    - by hmg
    Here's my code: public void readFile() throws IOException { System.out.println("Input file name: "); Scanner in = new Scanner(System.in); String readName = in.nextLine(); Scanner reader = new Scanner(new File(readName)); System.out.println("Reading file..."); while (reader.hasNextLine()) { System.out.println(reader.nextLine()); } System.out.println("File read."); Scanner inAgain = new Scanner(System.in); System.out.println("Would you like to read this into the current Diary?"); System.out.println("Warning: This will overwrite your current Diary!"); String readFileConfirm = inAgain.nextLine(); ArrayList<String> readData = new ArrayList<String>(); if (readFileConfirm.equalsIgnoreCase("yes")) { for (int i = 0; i < readData.size(); i++) { readData.add(reader.nextLine()); } System.out.println("Data added to extra array..."); System.out.println("Here are the contents."); for (int i = 0; i < readData.size(); i++) { System.out.println(readData.get(i)); } System.out.println("Contents read."); System.out.println("Now overwriting current Diary with read file..."); diary.clear(); for (int i = 0; i < diary.size(); i++) { diary.add(readData.get(i)); } System.out.println("New Diary created!"); System.out.println("Use 'recall' to see your new Diary!"); } else { System.out.println("Very well, returning to first command entry."); } } Thanks in advance! -h

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  • What's the reason behind the jumping GeneratedValue(strategy=GenerationType.TABLE) when not specifyi

    - by joeduardo
    Why do I need to add allocationSize=1 when using the @TableGenerator to ensure that the id wouldn't jump from 1, 2,... to 32,xxx, 65,xxx,... after a jvm restart? Is there a design reason for the need to specify the allocationSize? This snippet would produce the jumping ids @Id @GeneratedValue(strategy = GenerationType.TABLE) private Long id; Here's the modified snippet that produces the properly sequenced ids @Id @GeneratedValue(strategy = GenerationType.TABLE, generator = "account_generator") @TableGenerator(name = "account_generator", initialValue = 1, allocationSize = 1) private Long id;

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  • Vertical line on HxW canvas of pixels

    - by bobby williams
    I searched and found nothing. I'm trying to draw lines (simple y=mx+b ones) on a canvas of black pixels. It works fine, but no line occurs when it is vertical. I'm not sure why. My first if statement checks if the denominator is zero, therefore m is undefined and no need for a line equation. My second and third if statement check how steep it is and based on that, calculate the points in between. I don't think there is a need for other classes, since I think there is a bug in my code or I'm just not translating the mathematics into code properly. If more is needed, I'll be happy to post more. /** * Returns an collection of points that connects p1 and p2 */ public ArrayList getPoints() { ArrayList points = new ArrayList(); // checks to see if denominator in m is zero. if zero, undefined. if ((p2.getX() - p1.getX()) == 0) { for (int y = p1.getY(); y<p2.getY(); y++) { points.add(new Point(p1.getX(), y, getColor())); } } double m = (double)(p2.getY()-p1.getY())/(double)(p2.getX()-p1.getX()); int b = (int)(p1.getY() - (m * p1.getX())); // checks to see if slope is steep. if (m > -1 || m < 1) { for (int x = p1.getX(); x<p2.getX(); x++) { int y = (int) ((m*x)+b); points.add(new Point(x, y, getColor())); } } // checks to see if slope is not steep. if (m <= -1 || m >= 1) { for (int y = p1.getY(); y<p2.getY(); y++) { int x = (int) ((y-b)/m); points.add(new Point(x, y, getColor())); } } return points; }

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  • "Change" panel on jframe

    - by bog
    I have 2 panels, the first one is the menu, and the second is the application main panel. Firstly the menu panel shows up, than i need to switch to the other panel if a specific button is pressed on the menu (the menu is hidden but the app returns to it after running is completed). && i need to resize the frame too if it's possible. can i do this somehow?

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