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  • Making change recursively: How do I modify my algorithm to print all combinations?

    - by cb
    I have an algorithm that recursively makes change in the following manner: public static int makeChange(int amount, int currentCoin) { //if amount = zero, we are at the bottom of a successful recursion if (amount == 0){ //return 1 to add this successful solution return 1; //check to see if we went too far }else if(amount < 0){ //don't count this try if we went too far return 0; //if we have exhausted our list of coin values }else if(currentCoin < 0){ return 0; }else{ int firstWay = makeChange(amount, currentCoin-1); int secondWay = makeChange(amount - availableCoins[currentCoin], currentCoin); return firstWay + secondWay; } } However, I'd like to add the capability to store or print each combination as they successfully return. I'm having a bit of a hard time wrapping my head around how to do this. The original algorithm was pretty easy, but now I am frustrated. Any suggestions? CB

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  • Why is my file being cleared if I don't save it?

    - by Kat
    My program is suppose to maintain a collection of Photos in a PhotoAlbum. It begins by reading a folder of photos and adds them to my PhotoAlbum. It then prints a menu that allows the user to list all the photos, add a photo, find a photo, save, and quit the program. Right now if I run my program it will add the 100 photos to the PhotoAlbum, but if I quit the program without saving, it clears the file I am reading from even if I haven't added a photo or done anything to the PhotoAlbum and I'm not sure why. Here is my method for printing to a file: private static void saveFile(PrintWriter writer) { String result; ArrayList<Photo> temp = album.getPhotoAlbum(); for (int i = 0; i < temp.size(); i++){ result = temp.get(i).toString() + "\n"; writer.println(result); } writer.close(); } And where the PrintWriter is instantiated: File file = new File(args[0] + File.separator + "album.dat"); try { PrintWriter fout = new PrintWriter(new FileWriter(file)); fileWriter = fout; } catch (IOException e){ System.out.println("ReadFromFile: Folder " + args[0] + " is not found."); System.exit(0); } And where it is called in my runMenu Method: private static void runMainMenu(Scanner scan) { String input; do { showMainMenu(); input = scan.nextLine().toLowerCase(); switch (input.charAt(0)) { case 'p': System.out.println(album.toString()); break; case 'a': album.addPhoto(readPhoto(scan, t)); break; case 'f': findMenu(scan); break; case 's': saveFile(fileWriter); System.exit(0); break; case 'q': break; default: System.out.println("Invalid entry: " + input.charAt(0)); break; } } while (!input.equalsIgnoreCase("q")); }

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  • How to initiate chatting between two clients and two clients only, using applets and servlets?

    - by mithun1538
    Hello everyone, I first need to apologize for my earlier questions. (You can check my profile for them)They seemed to ask more questions than give answers. Hence, I am laying down the actual question that started all them absurd questions. I am trying to design a chat applet. Till now, I have coded the applet, servlet and communication between the applet and the servlet. The code in the servlet side is such that I was able to establish chatting between clients using the applets, but the code was more like a broadcast all feature, i.e. all clients would be chatting with each other. That was my first objective when I started designing the chat applet. The second step is chatting between only two specific users, much like any other chat application we have. So this was my idea for it: I create an instance of the servlet that has the 'broadcast-all' code. I then pass the address of this instance to the respective clients. 2 client applets use the address to then chat. Technically the code is 'broadcast-all', but since only 2 clients are connected to it, it gives the chatting between two clients feature. Thus, groups of 2 clients have different instances of the same servlet, and each instance handles chatting between two clients at a max. However, as predicted, the idea didn't materialize! I tried to create an instance of the servlet but the only solution for that was using sessions on the servlet side, and I don't know how to use this session for later communications. I then tried to modify my broadcast-all code. In that code, I was using classes that implemented Observer and Observable interfaces. So the next idea that I got was: Create a new object of the Observable class(say class_1). This object be common to 2 clients. 2 clients that wish to chat will use same object of the class_1. 2 other clients will use a different object of class_1. But the problem here lies with the class that implements the Observer interface(say class_2). Since this has observers monitoring the same type of class, namely class_1, how do I establish an observer monitoring one object of class_1 and another observer monitoring another object of the same class class_1 (Because notifyObservers() would notify all the observers and I can't assign a particular observer to a particular object)? I first decided to ask individual problems, like how to create instances of servlets, using objects of observable and observer and so on in stackoverflow... but I got confused even more. Can anyone give me an idea how to establish chatting between two clients only?(I am using Http and not sockets or RMI). Regards, Mithun. P.S. Thanks to all who replied to my previous (absurd) queries. I should have stated the purpose earlier so that you guys could help me better.

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  • Call the method of base Class which was over ridden

    - by Abhijith Venkata
    I have illustrated my question in this example class Car { public void start(){ System.out.println("Car Started!!!"); } } class Mercedes extends Car { public void start(){ System.out.println("Mercedes Started!!!"); } } Now, in my main program, I write Mercedes m = new Mercedes(); m.start(); It prints: Mercedes Started!!! How do I call the start() method of Car class using the same object so that the output can be Car Started!!!. Edit: Actually It was asked in an interview I attended. I gave the super keyword answer. But the interviewer denied it. He said he'd give me a hint and said Virtual Function. I have no idea how to use that hint.

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  • Using a JMS Session from different threads

    - by Evan
    From the javadoc for Session it states: A Session object is a single-threaded context for producing and consuming messages. So I understand that you shouldn't use a Session object from two different threads at the same time. What I'm unclear on is if you could use the Session object (or children such as a Queue) from a different thread than the one it created. In the case I'm working on, I'm considering putting my Session objects into a pool of available sessions that any thread could borrow from, use, and return to the pool when it is finished with it. Is this kosher? (Using ActiveMQ BTW, if that impacts the answer at all.)

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  • Should integration testing of DAOs be done in an application server?

    - by HDave
    I have a three tier application under development and am creating integration tests for DAOs in the persistence layer. When the application runs in Websphere or JBoss I expect to use the connection pooling and transaction manager of those application servers. When the application runs in Tomcat or Jetty, we'll be using C3P0 for pooling and Atomikos for transactions. Because of these different subsystems, should the DAO's be tested in a fully configured application server environment or should we handle those concerns when integration testing the service layer? Currently we plan on setting up a simple JDBC data source with non-JTA (i.e. resource-local) transactions for DAO integration testing, thus no application server is involved....but this leaves me wondering about environmental problems we won't uncover.

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  • Create NinePatch at Runtime

    - by Pedro Lopes
    Hello everybody! I have a business need to create the NinePatchDrawable objects at runtime, this is, an exterior .png image is received from a server and it has to be applied in a button's background (for example) as a nine patch. I have tried to create the NinePatchDrawable object, but the constructor asks me for a "byte[] chuck" that describes the patch. The thing is, I have no idea on how to build this chunck from a bitmap that does not have the 9patch information in it. Any ideas on this topic? Am I seeing the problem from a wrong perpective? Thanks!

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  • Server-initiated Rendering: EJB -> FacesContext?

    - by egbokul
    I've already asked this question on the Icefaces forum, but meanwhile I realized that this is a more generic problem. I'd like to update parts of a JSF page when I get a message in my MDB. The problem is, how do I get the FacesContext from the EJB container? In the message processing function FacesContext.getCurrentInstance() returns null. I've also tried to make a JSF managed bean be a MDB, but I couldn't (it seems you can't have both in the same class?). Since I'm a beginner in the JSF world I'm kind of stuck now. Is there a way to make it work? (Glassfish v3 + Netbeans 6.8, JSF2 + Icefaces 2.0 alpha2)

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  • Is there a simpler way to convert a byte array to a 2-byte-size hexadecimal string?

    - by Tom Brito
    Is there a simpler way of implement this? Or a implemented method in JDK or other lib? /** * Convert a byte array to 2-byte-size hexadecimal String. */ public static String to2DigitsHex(byte[] bytes) { String hexData = ""; for (int i = 0; i < bytes.length; i++) { int intV = bytes[i] & 0xFF; // positive int String hexV = Integer.toHexString(intV); if (hexV.length() < 2) { hexV = "0" + hexV; } hexData += hexV; } return hexData; } public static void main(String[] args) { System.out.println(to2DigitsHex(new byte[] {8, 10, 12})); } the output is: "08 0A 0C" (without the spaces)

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  • Killing Mysql prcoesses staying in sleep command.

    - by Shino88
    Hey I am connecting a MYSQL database through hibernate and i seem to have processes that are not being killed after they are finished in the session. I have called flush and close on each session but when i check the server the last processes are still there with a sleep command. This is a new problem which i am having and was not the case yesterday. Is there any way i can ensure the killng of theses processes when i am done with a session. Below is an example of one of my classes. public JSONObject check() { //creates a new session needed to add elements to a database Session session = null; //holds the result of the check in the database JSONObject check = new JSONObject(); try{ //creates a new session needed to add elements to a database SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); session = sessionFactory.openSession(); if (justusername){ //query created to select a username from user table String hquery = "Select username from User user Where username = ? "; //query created Query query = session.createQuery(hquery); //sets the username of the query the values JSONObject contents query.setString(0, username); // executes query and adds username string variable String user = (String) query.uniqueResult(); //checks to see if result is found (null if not found) if (user == null) { //adds false to Jobject if not found check.put("indatabase", "false"); } else { check.put("indatabase", "true"); } //adds check to Jobject to say just to check username check.put("justusername", true); } else { //query created to select a username and password from user table String hquery = "Select username from User user Where username = :user and password = :pass "; Query query = session.createQuery(hquery); query.setString("user", username); query.setString("pass", password); String user = (String) query.uniqueResult(); if(user ==null) { check.put("indatabase", false); } else { check.put("indatabase", true); } check.put("justusername", false); } }catch(Exception e){ System.out.println(e.getMessage()); //logg.log(Level.WARNING, " Exception", e.getMessage()); }finally{ // Actual contact insertion will happen at this step session.flush(); session.close(); } //returns Jobject return check; }

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  • Using a Session Scoped Bean

    - by jboyd
    The following code is returning null: private MyAppUser getMyAppUser(HttpSession session) { MyAppUser myAppUser = (MyAppUser) session.getAttribute("myAppUserManager"); return myAppUser; } Despite the fact that I have the following in my context: <bean id="myAppUserManager" class="com.myapp.profile.MyAppUser" scope="session"/> This doesn't make any sense to me, the "myAppUser" bean is a bean that absolutely can never be null, and I need to be able to reference it from controllers, I don't need it in services or repositories, just controllers, but it doesn't seem to be getting stored in the session, the use case is extremely simple, but I haven't been able to get to the bottom of what's wrong, or come up with a good workaround

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  • Using ControllerClassNameHandlerMapping with @Controller and extending AbstractController

    - by whiskerz
    Hey there, actually I thought I was trying something really simple. ControllerClassNameHandlerMapping sounded great to produce a small spring webapp using a very lean configuration. Just annotate the Controller with @Controller, have it extend AbstractController and the configuration shouldn't need more than this <context:component-scan base-package="test.mypackage.controller" /> <bean id="urlMapping" class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping" /> to resolve my requests and map them to my controllers. I've mapped the servlet to "*.spring", and calling <approot>/hello.spring All I ever get is an error stating that no mapping was found. If however I extend the MultiActionController, and do something like <approot>/hello/hello.spring it works. Which somehow irritates me, as I would have thought that if that is working, why didn't my first try? Does anyone have any idea? The two controllers I used looked like this @Controller public class HelloController extends AbstractController { @Override protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception { ModelAndView modelAndView = new ModelAndView("hello"); modelAndView.addObject("message", "Hello World!"); return modelAndView; } } and @Controller public class HelloController extends MultiActionController { public ModelAndView hello(HttpServletRequest request, HttpServletResponse response) throws Exception { ModelAndView modelAndView = new ModelAndView("hello"); modelAndView.addObject("message", "Hello World!"); return modelAndView; } }

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  • How do I subtract a binding using a Guice module override?

    - by Jimmy Yuen Ho Wong
    So according to my testing, If you have something like: Module modA = new AbstractModule() { public void configure() { bind(A.class).to(AImpl.class); bind(C.class).to(ACImpl.class); bind(E.class).to(EImpl.class); } } Module modB = New AbstractModule() { public void configure() { bind(A.class).to(C.class); bind(D.class).to(DImpl.class); } } Guice.createInjector(Modules.overrides(modA, modB)); // gives me binding for A, C, E AND D with A overridden to A->C. But what if you want to remove the binding for E in modB? I can't seem to find a way to do this without having to break the bind for E into a separate module. Is there a way?

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  • How do I add a library in Eclipse?

    - by jul
    hi, I downloaded the Gson library from http://code.google.com/p/google-gson/. The archive contains the following jar files: google-gson-1.3/gson-1.3-javadoc.jar google-gson-1.3/gson-1.3.jar google-gson-1.3/gson-1.3-sources.jar How do I set my Eclipse to be able to use the package in my projects? Where do I put the documentation? Thanks jul

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  • Anybody using Qi4J

    - by Jon
    I was reading an InfoQ article on Composite Oriented Programming earlier on: http://www.infoq.com/articles/Composite-Programming-Qi4j I was interested in finding out whether anybody is currently using (or has used) the Qi4j framework at all? How does it compares to using a traditional dependency injection framework such as Spring for wiring classes together. Is the resulting object graph (based on mixins rather than classes) easier to deal with from a maintenance point of view?

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  • Unable to set mouse cursor JLayeredPane

    - by Ones3k2
    I'm running into a problem that I can't seem to figure out nor find the answer anywhere on the web. I've got a JLayeredPane and when it only has one child Panel I am able to correctly set the cursor using setCursor(). The cursor shows up and everything is fine. But when I add an additional JPanel into the JLayeredPane the cursor no longer shows up for example this works: m_layeredPane = new JLayeredPane(); m_layeredPane.setLayout(new WBLayoutManager()); m_layeredPane.add(m_mediaPanel, new Integer(0)); // m_layeredPane.add(m_whiteboardPanel, new Integer(1)); m_layeredPane.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR)); // WORKS but this doesn't: m_layeredPane = new JLayeredPane(); m_layeredPane.setLayout(new WBLayoutManager()); m_layeredPane.add(m_mediaPanel, new Integer(0)); m_layeredPane.add(m_whiteboardPanel, new Integer(1)); m_layeredPane.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR)); // FAILS Anyone know how i can get custom cursors working within a JLayeredPane

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  • error in midlet while implementing command..

    - by garima
    hi I have imported import com.sun.lwuit.Command; import javax.microedition.midlet.; import javax.microedition.lcdui.; in my code but still the following errors are coming... exitCommand = new Command("Exit", Command.EXIT, 2); //line 1 textbox.addCommand(exitCommand); //line 2 Command.EXIT cannot be resolved.. The method addCommand(Command) in the type Displayable is not applicable for the arguments (Command)

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  • JSF/Seam - call one component method for many radio groups

    - by purecharger
    I've got the following jsf page: <h:form> <ui:repeat value="#{list.categories}" var="cat"> <h:selectOneRadio id="sel1Rad" value="#{list.choose}" layout="pageDirection"> <f:selectItems value="#{list.names}"/> </h:selectOneRadio> </ui:repeat> <h:commandButton id="submit" action="#{list.submit}" value="Submit"/> </h:form> And a component named list. The variable cat is injected to the component, used by the method list.getNames(). What I am trying to have happen is to have list.choose() be called for each radio group. I'm not sure if this is possible with Seam. Going by the booking example distributed with Seam, there is a distinct separate method for each selectOneRadio or selectOneMenu group. Since I have an unknown number of categories, I can't / don't want to define a method for each possible choice. When I submit the form, all my choices are sent in the POST, I just don't know the correct way to tell Seam how to dispatch them to my component. Any help is appreciated!

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  • storage service with google app engine.

    - by Bunny Rabbit
    i've been assigned a project to create a filestorage service on google applet engine.but i am really doubtful wheather it's possible or not given the 30 sec limit to process the response and moreover its the bigtable is just a database system not a storage server .am i correct ?

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  • How can i use Stopwatch [ apache ] to calculate the time taken by a method?

    - by Rakesh Juyal
    I am using StopWatch [ apache ] to get the time taken by my method. The approach i am following is StopWatch stopWatch = new StopWatch(); stopWatch.start(); myMethod(); stopWatch.stop(); logger.info( "Time taken by myMethod: " + stopWatch.getTime() + " millisecs"); stopWatch.reset(); stopWatch.start(); anotherMethod(); stopWatch.stop(); logger.info( "Time taken by anotherMethod: " + stopWatch.getTime() + " millisecs"); Thats the only thing i know about StopWatch :). How/when to use split(), unsplit(), getSplitTime(),suspend()... ?

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  • Hibernate: deletes not cascading for self-referencing entities

    - by jwaddell
    I have the following (simplified) Hibernate entities: @Entity @Table(name = "package") public abstract class Package { protected Content content; @ManyToOne(cascade = {javax.persistence.CascadeType.ALL}) @JoinColumn(name = "content_id") @Fetch(value = FetchMode.JOIN) public Content getContent() { return content; } public void setContent(Content content) { this.content = content; } } @Entity @Table(name = "content") public class Content { private Set<Content> subContents = new HashSet<Content>(); @ManyToMany(fetch = FetchType.EAGER) @JoinTable(name = "subcontents", joinColumns = {@JoinColumn(name = "content_id")}, inverseJoinColumns = {@JoinColumn(name = "elt")}) @Cascade(value = {org.hibernate.annotations.CascadeType.DELETE, org.hibernate.annotations.CascadeType.REPLICATE}) @Fetch(value = FetchMode.SUBSELECT) public Set<Content> getSubContents() { return subContents; } public void setSubContents(Set<Content> subContents) { this.subContents = subContents; } } So a Package has a Content, and a Content is self-referencing in that it has many sub-Contents (which may contain sub-Contents of their own etc). The relationships are required to be ManyToOne (Package to Content) and ManyToMany (Content to sub-Contents) but for the case I am currently testing each sub-Content only relates to one Package or Content. The problem is that when I delete a Package and flush the session, I get a Hibernate error stating that I'm violating a foreign key constraint on table subcontents, with a particular content_id still referenced from table subcontents. I've tried specifically (recursively) deleting the Contents before deleting the Package but I get the same error. Is there a reason why this entity tree is not being deleted properly?

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  • How could I get an .ear's filesize at runtime?

    - by adam
    I started out attempting to do this with the Length ant task, but realized that that would be done before the ear is packaged. Packaging the ear, then checking the file size, and then placing it in the ear would effect the size of the ear. Is there a way to get the ear's size programmatically at run-time? Or perhaps an MBean that would have that information?

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