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  • Exception handling in Iterable

    - by Maas
    Is there any way of handling -- and continuing from -- an exception in an iterator while maintaining the foreach syntactic sugar? I've got a parser that iterates over lines in a file, handing back a class-per-line. Occasionally lines will be syntactically bogus, but that doesn't necessarily mean that we shouldn't keep reading the file. My parser implements Iterable, but dealing with the potential exceptions means writing for (Iterator iter = myParser.iterator(); iter.hasNext(); ) { try { MyClass myClass = iter.next(); // .. do stuff .. } catch (Exception e) { // .. do exception stuff .. } } .. nothing wrong with that, but is there any way of getting exception handling on the implicit individual iter.next() calls in the foreach construct?

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  • Does add() on LinkedBlockingQueue notify waiting threads?

    - by obvio171
    I have a consumer thread taking elements from a LinkedBlockingQueue, and I make it sleep manually when it's empty. I use peek() to see if the queue empty because I have to do stuff because sending the thread to sleep, and I do that with queue.wait(). So, when I'm in another thread and add()an element to the queue, does that automatically notify the thread that was wait()ing on the queue?

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  • Time complexity O() of isPalindrome()

    - by Aran
    I have this method, isPalindrome(), and I am trying to find the time complexity of it, and also rewrite the code more efficiently. boolean isPalindrome(String s) { boolean bP = true; for(int i=0; i<s.length(); i++) { if(s.charAt(i) != s.charAt(s.length()-i-1)) { bP = false; } } return bP; } Now I know this code checks the string's characters to see whether it is the same as the one before it and if it is then it doesn't change bP. And I think I know that the operations are s.length(), s.charAt(i) and s.charAt(s.length()-i-!)). Making the time-complexity O(N + 3), I think? This correct, if not what is it and how is that figured out. Also to make this more efficient, would it be good to store the character in temporary strings?

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • interfacing: simplified

    - by code wombat
    i've been doing some research on interfaces and a simple layman's explanation for what it truly is. For some reason people love using overly complex explanations and jargon to explain truly simple concepts (guess it makes them feel big) and i have a gut feeling it's the same in this case. so from what i could grasp, it seems like interfaces are nothing more than a way to reserve method names, their return type if any, and the type and amount of arguments they accept. so when a class implements an interface (or interfaces) it is forced to define the body of each method from the interface(s). Am i on the nose with this one or do i need to keep digging? p.s. i know javascript doesn't have support for interfaces, but i still need to understand the concept because there are quite a few places where it's shown how to emulate to an extent.

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  • How to disable a container and its children in Swing

    - by Fuzzy76
    I cannot figure out a way to disable a container AND its children in Swing. Is Swing really missing this basic feature? If I do setEnabled(false) on a container, its children are still enabled. My GUI structure is pretty complex, and doing a traversion of all elements below the container is not an option. Neither is a GlassPane on top of the container (the container is not the entire window).

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  • In JSF, how to handle repeating over a list that mutates

    - by Jon
    Hello, In a JSF page, I am iterating over a list of items provided by a session-scoped backing bean. The list needs to be kept up-to-date, so it is replaced with a fresh list every X minutes by a thread (in a thread-safe way). On my page, for each item I provide some text inputs and an "Update" button. If the list is refreshed before I hit "Update", the update does not happen (which is my problem). I happen to be using a4j:repeat, but I think this could also apply to other methods of iteration, including using dataTables. Any thoughts on how I can do this in a non-hackish way? Thanks!

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  • How to add chain of certificate in spring ws client request

    - by hudi
    I have simply spring ws client which sending request to some url: @SuppressWarnings("unchecked") private JAXBElement<O> sendSyncSoapRequest(final JAXBElement<I> req, final String iszrUrl) { if (iszrUrl != null) { return (JAXBElement<O>) this.wsTemplate.marshalSendAndReceive(iszrUrl, req); } else { return (JAXBElement<O>) this.wsTemplate.marshalSendAndReceive(req); } } Now I need attach chain of certificate to the soap request. How should I do this ? Please help

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  • Check if table exists

    - by Dmitry
    I have a desktop application with a database embedded in it. When I execute my program I need to check that specific table exists, or create it if not. Given a Connection object named conn for my database, how could I check this?

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  • How to discard time intervals with Time Series / XYPlots using JFreeChart?

    - by Alex Arnon
    Hi All, I am building a set of chart displays, one of which is for a month display of daily trading - that is, one point of data per day (closing). Since there is no trade during weekends and holidays, I need to discard these data points. Not only that, but data points should still appear adjacent to each other, regardless of any gaps in time. This can be seen in any such chart e.g. in the 3 month graph for Nasdaq on Yahoo Finance - see how weekends are skipped. My question is: how should one correctly implement this in JFreeChart? Thanks in advance!

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  • can't explain NullPointerException

    - by John Pope
    In the following code, i have a method to get a Vector of persons with the same zodiac sign. persoane is a Vector. I keep getting a NullPointerException at the if condition (persoane is definetly not null). I am unable to see why. Any help would be greatly appreciated public Vector<Persoana> cautaDupaZodie(String zodie) { Vector<Persoana> rezultat= new Vector<Persoana>(); for(int i=0; i<persoane.size(); i++) { if(persoane.get(i).getData().getZodie().equals(zodie)) //the exception occurs here { rezultat.add(persoane.get(i)); } } return rezultat; }

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  • Can Tomcat provide seperate (or HTTPS only) sessions for HTTPS requests?

    - by Joe
    I have a web application which contains both secure (SSL) and non-secure pages. A user can login to the site and must appear logged-in in both the SSL and non-SSL areas. (NB. SSL isn't implemented via Tomcat, but via Apache HTTPD servers which sit in front of Tomcat - so Tomcat has no SSL configuration.) The logged-in state is currently maintained via a servlet session (using Tomcat's vanilla session management). The obvious issue with this approach is that the JSESSIONID cookie is transported over both HTTP and HTTPS connections, meaning that it's potentially possible to intercept it and hijack the session. Are there any solutions to this without rolling our own session management (i.e. does Tomcat cater for this situation)? I'm prepared to implement our own session management, but don't want to reinvent something that may already be supported.

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  • Can I do a URL Rewrite to a different Tomcat instance?

    - by RodeoClown
    Is is possible to use Tuckey's URL Rewrite to rewrite to a different Tomcat instance? I have it working using crossContext="true" rewriting to a different servlet on the same tomcat instance, but our production server has multiple tomcat instances running and I want to rewrite to one of them instead? If it's not possible using the URL Rewrite filter, is there another way of doing it? Thanks.

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  • Spring MVC 3.0 Rest problem

    - by Gidogeek
    Hi Guys, I'm trying out Spring MVC 3.0 for the first time and like to make it RESTfull. This is my controller: @Controller @RequestMapping(value = "/product") @SessionAttributes("product") public class ProductController { @Autowired private ProductService productService; public void setProductValidator(ProductValidator productValidator, ProductService productService) { this.productService = productService; } @RequestMapping(method = RequestMethod.GET) public Product create() { //model.addAttribute(new Product()); return new Product(); } @RequestMapping(method = RequestMethod.POST) public String create(@Valid Product product, BindingResult result) { if (result.hasErrors()) { return "product/create"; } productService.add(product); return "redirect:/product/show/" + product.getId(); } @RequestMapping(value = "/show/{id}", method = RequestMethod.GET) public Product show(@PathVariable int id) { Product product = productService.getProductWithID(id); if (product == null) { //throw new ResourceNotFoundException(id); } return product; } @RequestMapping(method = RequestMethod.GET) public List<Product> list() { return productService.getProducts(); } } I have 2 questions about this. I'm a believer in Convention over Configuration and therefor my views are in jsp/product/ folder and are called create.jsp , list.jsp and show.jsp this works relatively well until I add the @PathVariable attribute. When I hit root/product/show/1 I get the following error: ../jsp/product/show/1.jsp" not found how do I tell this method to use the show.jsp view ? If I don't add the RequestMapping on class level my show method will be mapped to root/show instead of root/owner/show how do I solve this ? I'd like to avoid using the class level RequestMapping.

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  • In ArrayBlockingQueue, why copy into ReentrantLock 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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  • JTable - Getting a cell into Edit mode on pressing Tab

    - by Luhar
    This is possibly has a trivial solution, but I am at the end of my tether so I hope somebody can help out. I use a JTable which has a custom renderer and a custom editor for a set of columns. The renderer uses a JLabel component and the editor uses a JSpinner component. Our users want to be able to enter values in a column, and then press TAB or ENTER to move to the next editable cell in the table. If I understand correctly, this is the default behaviour for a JTable. However, this doesn't seem to work correctly for me. Until the user clicks on the cell, only the JLabel is displayed. The JSpinner (i.e. CellEditor) is only displayed when a user double clicks on the cell. So, it looks like the cell is going into "edit" mode only on MouseEvents, but not when it has focus. How do I get the cell to go into edit mode as soon as it has focus?

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  • sql query not executing

    - by sarah
    Hi, Not able to execute a query ,i need to check if end date is greater than today in the following query Getting an error invalid query select * from table1 where user in ('a') and END_DATE >'2010-05-22' getting an error liter string does not match

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  • Weather API to mobile platform

    - by Alex
    Hello everybody! I would like to ask from you guys/girls somebody used radar image api in MOBILE PLATFORM? I got some good provider but the user agreement don`t allow to use it in mobile platform. Even some good weather forecast API exists? (with moon phase,5-7 days forecast) and radar images ? Maybe search by US zip code?

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  • JPA: what is the proper pattern for iterating over large result sets?

    - by Caffeine Coma
    Let's say I have a table with millions of rows. Using JPA, what's the proper way to iterate over a query against that table, such that I don't have all an in-memory List with millions of objects? I suspect that the following will blow up if the table is large: List<Model> models = entityManager().createQuery("from Model m", Model.class).getResultList(); for (Model model : models) { // do something with model } Is pagination (looping and manually updating setFirstResult()/setMaxResult()) really the best solution?

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  • Is there a version of postActionEvent for KeyEvent (specifically for a JTextArea)?

    - by Brian Pelc
    I'm writing a program that contains multiple JTextFields and 2 JTextAreas within an input panel. I have a submit button on the bottom. I have it set up so when a user types something into each field (including the JTextAreas) and hits the Enter key, it updates a text file, and when they press the submit button it updates the file then outputs a new version of it in the local directory. If the user presses Enter in any of the fields, it validates their input, however, I want to re-validate all fields when they press the submit button. Each field (again, JTextAreas included) has it's own validation check within its ActionListener or KeyListener (for the JTextAreas). It's easy enough to use postActionEvent() for the JTextFields, but is there a similar method for the JTextAreas to force fire a KeyEvent? I don't want to duplicate code and consume memory by re-writing the validation for those 2 Components inside the ActionEvent for the JButton. Unfortunately, I can't provide a sample because I'm writing the program on a classified machine (PC).

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  • Overriding a method in statically created objects

    - by I82Much
    All, Due to a bug in a library I'm using, I need to override the dispose() method on all objects extending a certain class and make it a NO-OP. I know that if I'm making new instances of the classes directly, this is easy to do: layerManager = new LayerManagerLayer(wwd) { @Override public void dispose() {} }; The problem is that a lot of the object instances I get are not directly constructed by my client code, but instead are created via static library method calls. // Here I want to override the dispose method, but I cannot. Layer l = ShapefileLoader.makeShapefileLayer(this.getClass().getResource("polylines10.shp")); Is there a way I can inject my dispose method into that statically created object without modifying the original sourcecode?

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  • How to read log4j output to a web page?

    - by Ran
    I have a web page, used for admin purposes, which runs a task (image fetching from a remote site). In order to be able to debug the task using the browser only, no ssh etc, I'd like to be able to read all log output from the executing thread and spit it out to the web page. The task boils down to: Changing log level for current thread at the beginning of the call and restore when the call is done. Reading all log output by current thread and storing it in a string. So in pseudocode my execute() method would look like this: (I'm using struts2) public String execute() throws Exception { turnLoggingLevelToDebugOnlyForThisThread() ... do stuff... restoreLoggingLevelForThisThread() String logs = readAllLogsByThisThread(); } Can this be done with log4j? I'm using tomcat, struts2, log4j and slf4j.

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