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  • How to design authentication in a thick client, to be fail safe?

    - by Jay
    Here's a use case: I have a desktop application (built using Eclipse RCP) which on start, pops open a dialog box with 'UserName' and 'Password' fields in it. Once the end user, inputs his UserName and Password, a server is contacted (a spring remote-servlet, with the client side being a spring httpclient: similar to the approaches here.), and authentication is performed on the server side. A few questions related to the above mentioned scenario: If said this authentication service were to go down, what would be the best way to handle further proceedings? Authentication is something that I cannot do away with. Would running the desktop client in a "limited" mode be a good idea? For instance, important features/menus/views will be disabled, rest of the application will be accessible? Should I have a back up authentication service running on a different machine, working as a backup? What are the general best-practices in this scenario? I remember reading about google gears and how it would let you edit and do stuff offline - should something like this be designed? Please let me know your design/architectural comments/suggestions. Appreciate your help.

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  • Simple explaination of Arraylists

    - by Jeremy
    I'm new to programming and I'm looking for a simple answer to build my foundation of understanding Arrays. I've used google and searched this site. After a bit of trial and error I get how to make and reference Arrays like thing[3] gets you the fourth thing in the thing array(since 0 is the first). which lets me do something like thing[3].getStupidNumber() to get the StupidNumber of the 4th thing in the thing array. Then I get to ArrayLists which seem to have much more utility but I cant make logical sense of them like Arrays. When i search I cant find this or word this correctly and thus far everything else I've learned clicked easily. so say I make an ArrayList thing with 5 things in it. how do i get to the .getStupidNumber() method inside the fourth thing, if possible? I think if I learn this I can learn the rest on my own. Thanks!

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  • Unnecessary 'else' statement

    - by Vitalii Fedorenko
    As you know, in Eclipse you can turn on "Unnecessary 'else' statement" check that will trigger on if-then-else with premature return. And, from my experience, there are two most possible situations when use such statement: 1) Pre-check: if (validate(arg1)) { return false; } doLotOfStuff(); 2) Post-check: doLotOfStuff(); if (condition) { return foo; } else { return bar; } In the second case, if the trigger is on, Eclipse will suggest you to change the code to: doLotOfStuff(); if (condition) { return foo; } return bar; However, I think that the return with else statement is more readable as it is like direct mapping of business logic. So I am curios if this "Unnecessary 'else' statement" code convention is widespread or else statement is more preferable?

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  • implementation of a queue using a circular array

    - by matin1234
    Hi I have found these algorithms in the internet but I can not understand that why in the enqueue method we compare size with N-1??? please help me thanks!! Algorithm size(): return (N-f+r)mod N Algorithm enqueue(e): if size()=N-1 then throw a FullQueueException Q[r]<---e r<----(r+1)mod N

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  • ValidatorResources not found in application

    - by jojolapin
    I had been told to deploy a *.war file within tomcat and this application should be working fine. But for an unknown reason all I get is: System Exception: javax.servlet.jsp.JspException: ValidatorResources not found in application scope under key "org.apache.commons.validator.VALIDATOR_RESOURCES" I know that this application has been developed with STRUTS and I can obtain the source. But as I am not a specialist in this field, I come to ask for some help. Could you tell me what file could generate this exception please?

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  • Is there a way to filter out offensive words from Jcaptcha?

    - by elduff
    We are using JCaptcha for a captcha tool in a small app that my team is writing. However, just during development time (on a small team - 4 of us), we've run across a number of curse words and other potentially offensive words for the actual captchas. Is there a way to filter out potentially offensive words so that they are not presented to the user?

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  • Find top N elements in a Multiset from Google Collections?

    - by dfrankow
    A Google Collections Multiset is a set of elements each of which has a count (i.e. may be present multiple times). I can't tell you how many times I want to do the following Make a histogram (exactly Multiset) Get the top N values from the histogram Examples: top 10 URLs, top 10 tags, ... What is the canonical way to do #2 given a Multiset? Here is a blog post about it, but that code is not quite what I want. First, it returns everything, not just top N. Second, it copies (is it possible to avoid a copy?). Third, I usually want a deterministic sort, i.e. tiebreak if counts are equal.

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  • getting IllegalAccessException when accessing a protected method from parent from inner class

    - by EnToutCas
    I got a very weird problem and a weird solution: class Parent { protected void aProtectedMethod() { doSomething(); } } class Child extends Parent { void anotherMethod() { new SomeInterface() { public void interfaceMethod() { aProtectedMethod(); } }; } } When child.anotherMethod() is run, I got IllegalAccessException at myProtectedMethod(), saying my inner class doesn't have access to the Parent class... However, if I add: protected void aProtectedMethod() { super.aProtectedMethod(); } in my Child class, everything is fine... I wonder why this is?

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  • When I try to redefine a variable, I get an index out of bounds error

    - by user2770254
    I'm building a program to act as a calculator with memory, so you can give variables and their values. Whenever I'm trying to redefine a variable, a = 5, to a = 6, I get an index out of bounds error. public static void main(String args[]) { LinkedHashMap<String,Integer> map = new LinkedHashMap<String,Integer>(); Scanner scan = new Scanner(System.in); ArrayList<Integer> values = new ArrayList<>(); ArrayList<String> variables = new ArrayList<>(); while(scan.hasNextLine()) { String line = scan.nextLine(); String[] tokens = line.split(" "); if(!Character.isDigit(tokens[0].charAt(0)) && !line.equals("clear") && !line.equals("var")) { int value = 0; for(int i=0; i<tokens.length; i++) { if(tokens.length==3) { value = Integer.parseInt(tokens[2]); System.out.printf("%5d\n",value); if(map.containsKey(tokens[0])) { values.set(values.indexOf(tokens[0]), value); variables.set(variables.indexOf(tokens[0]), tokens[0]); } else { values.add(value); } break; } else if(tokens[i].charAt(0) == '+') { value = addition(tokens, value); System.out.printf("%5d\n",value); variables.add(tokens[0]); if(map.containsKey(tokens[0])) { values.set(values.indexOf(tokens[0]), value); variables.set(variables.indexOf(tokens[0]), tokens[0]); } else { values.add(value); } break; } else if(i==tokens.length-1 && tokens.length != 3) { System.out.println("No operation"); break; } } map.put(tokens[0], value); } if(Character.isDigit(tokens[0].charAt(0))) { int value = 0; if(tokens.length==1) { System.out.printf("%5s\n", tokens[0]); } else { value = addition(tokens, value); System.out.printf("%5d\n", value); } } if(line.equals("clear")) { clear(map); } if(line.equals("var")) { variableList(variables, values); } } } public static int addition(String[] a, int b) { for(String item : a) { if(Character.isDigit(item.charAt(0))) { int add = Integer.parseInt(item); b = b + add; } } return b; } public static void clear(LinkedHashMap<String,Integer> b) { b.clear(); } public static void variableList(ArrayList<String> a, ArrayList<Integer> b) { for(int i=0; i<a.size(); i++) { System.out.printf("%5s: %d\n", a.get(i), b.get(i)); } } I included the whole code because I'm not sure where the error is arising from.

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  • Collections removeAll method

    - by srinannapa
    I would like to know if something like below is possible , list<**MyObject**>.**removeAll**(list<**String**>) I hope the context is understandable. The list<MyObject : is a ArrayList<MyObject The list<String : is a ArrayList<String I know this can be achieved by overriding equals method in MyObject class. I would like to know if any other choice is prsent. Thanks,Srinivas N

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  • Is this a correct way to stop Execution Task

    - by Yan Cheng CHEOK
    I came across code to stop execution's task. private final ExecutorService executor = Executors.newSingleThreadExecutor(); public void stop() { executor.shutdownNow(); try { executor.awaitTermination(100, TimeUnit.DAYS); } catch (InterruptedException ex) { log.error(null, ex); } } public Runnable getRunnable() { return new Runnable() { public void run() { while (!Thread.currentThread().isInterrupted()) { // What if inside fun(), someone try to clear the interrupt flag? // Say, through Thread.interrupted(). We will stuck in this loop // forever. fun(); } } }; } I realize that, it is possible for Runnable to be in forever loop, as Unknown fun may Thread.sleep, clear the interrupt flag and ignore the InterruptedException Unknown fun may Thread.interrupted, clear the interrupt flag. I was wondering, is the following way correct way to fix the code? private final ExecutorService executor = Executors.newSingleThreadExecutor(); private volatile boolean flag = true; public void stop() { flag = false; executor.shutdownNow(); try { executor.awaitTermination(100, TimeUnit.DAYS); } catch (InterruptedException ex) { log.error(null, ex); } } public Runnable getRunnable() { return new Runnable() { public void run() { while (flag && !Thread.currentThread().isInterrupted()) { // What if inside fun(), someone try to clear the interrupt flag? // Say, through Thread.interrupted(). We will stuck in this loop // forever. fun(); } } }; }

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  • Multivalue Mysql Inserts using HibernateTemplate

    - by Langali
    I am using Spring HibernateTemplate and need to insert hundreds of records into a mysql database every second. Not sure what is the most performant way of doing it, but I am trying to see how the multi value mysql inserts do using hibernate. String query = "insert into user(age, name, birth_date) values(24, 'Joe', '2010-05-19 14:33:14'), (25, 'Joe1', '2010-05-19 14:33:14')" getHibernateTemplate().execute(new HibernateCallback(){ public Object doInHibernate(Session session) throws HibernateException, SQLException { return session.createSQLQuery(query).executeUpdate(); } }); But I get this error: 'could not execute native bulk manipulation query.' Please check your query ..... Any idea of I can use a multi value mysql insert using Hibernate? or is my query incorrect? Any other ways that I can improve the performance? I did try the saveOrUpdateAll() method, and that wasn't good enough!

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  • How do I calculate a good hash code for a list of strings?

    - by Ian Ringrose
    Background: I have a short list of strings. The number of strings is not always the same, but are nearly always of the order of a “handful” In our database will store these strings in a 2nd normalised table These strings are never changed once they are written to the database. We wish to be able to match on these strings quickly in a query without the performance hit of doing lots of joins. So I am thinking of storing a hash code of all these strings in the main table and including it in our index, so the joins are only processed by the database when the hash code matches. So how do I get a good hashcode? I could: Xor the hash codes of all the string together Xor with multiply the result after each string (say by 31) Cat all the string together then get the hashcode Some other way So what do people think? (If you care we are using .NET and SqlServer)

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  • Why does the android emulator camera stop unexpectedly?

    - by user490074
    I am using Android 2.2 (API Level 8). The camera is enabled in the manifest. When I try the camera icon provided by the emulator model, it runs for a few seconds showing a gray box moving around a black and white checkerboard, then dies with the error message: Sorry! The application Camera (process com.android.camera) has stopped unexpectedly. Please try again. Trying again, of course, doesn't help. I am using the provided emulator camera to compare behavior with a camera application I am working on. Why does the android emulator camera stop unexpectedly?

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  • I have to make a simple app that connects devices in a network, but I have no idea of how to this

    - by Gabriel Casado
    I want to write an App for android that has only one ListView. The App will constantly search for anything (mobile devices, desktops, etc.) that is connected in the wifi network. The problem is, I have no idea how to do this. What do I need to study? I comprehend I'd need to use a Thread or a Runnable to constantly search for those devices. Also I know very little about TCP, UDP or any internet protocols. So, can someone give me a basis of what I need to learn to develop this App?

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  • Creating a shared HSQLDB database

    - by Robert Munteanu
    In-process HSQLDB database are not expected to be opened by others, even for file-based storage. The documentation hints that this is possible: Server Modes, Advanced Topics, but I've not yet found a URL for how to activate this behaviour. Did anyone do this so they can share how to?

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  • Getting a JFrame's actual current location

    - by Ian Fellows
    Hello community, I am trying to create a (child) JFrame which slides out from underneath one side of a second (parent) JFrame. The goal is to then have the child follow the parent around when it is moved, and respond to resizing events. This is somewhat related to this question. I have tried using a ComponentListener, but with this method the child only moves once the parent has come to a stop, whereas I would like the child to move as the parent is dragged around the screen. Another option I attempted was to start a new refresher thread that continually updated the child's location using getLocation() or getLocationOnScreen(), but the lag was the same as with ComponentListener. Is there a way to get the true actual location of a JFrame even in the midst of a drag? or if not, is there a way to get the effect of a sheet sliding out from underneath and following the Frame around?

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