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  • Benefits of arrays

    - by Vitalii Fedorenko
    As I see it, the advantages of List over array are pretty obvious: Generics provide more precise typing: List<Integer>, List<? extends Number>, List<? super Integer>. List interface has a bunch useful methods: addAll, remove etc. While for arrays all standard operations except get/set must be performed in a procedure manner by passing it to a static method. Collections offer different implementations like ArrayList, LinkedList, unmodifieable and synchronized lists, which can be hidden under common List interface. OOB length control. As disadvantages I can only mention absence of syntactic sugar and runtime type check. At the same time supporting of both structures requires frequent using of asList and toArray methods, which makes code less readable. So I am curious if there are any important benefits of using arrays that I miss.

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  • Have something loaded only when JList item is visibile

    - by elvencode
    Hello, i'm implementing a Jlist populated with a lot of elements. Each element corresponds to a image so i'd like to show a resized preview of them inside each row of the list. I've implemented a custom ImageCellRenderer extending the Jlabel and on getListCellRendererComponent i create the thumbnail if there'snt any for that element. Each row corresponds to a Page class where i store the path of the image and the icon applied to the JLabel. Each Page object is put inside a DefaultListModel to populate the JList. The render code is something like this: public Component getListCellRendererComponent( JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) { Page page = (Page) value; if (page.getImgIcon() == null) { System.out.println(String.format("Creating thumbnail of %s", page.getImgFilename())); ImageIcon icon = new ImageIcon(page.getImgFilename()); int thumb_width = icon.getIconWidth() > icon.getIconHeight() ? 128 : ((icon.getIconWidth() * 128) / icon.getIconHeight()); int thumb_height = icon.getIconHeight() > icon.getIconWidth() ? 128 : ((icon.getIconHeight() * 128) / icon.getIconWidth()); icon.setImage(getScaledImage(icon.getImage(), thumb_width, thumb_height)); page.setImgIcon(icon); } setIcon(page.getImgIcon()); } I was thinking that only a certain item is visibile in the List the cell renderer is called but i'm seeing that all the thumnails are created when i add the Page object to the list model. I've tried to load the items and after set the model in the JList or set the model first and after starting appending the items but the results are the same. Is there any way to load the data only when necessary or do i need to create a custom control like a JScrollPanel with stacked items inside where i check myself the visibility of each elements? Thanks

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  • user enter data to different arrays

    - by user2900469
    This is fragment of my code (arrays as you can see): double[] Price; String[] names; int[] Quantity; Price = new double[5]; names = new String[5]; Quantity = new int[5]; Price[1] = 3.10; Price[2] = 7.80; Price[3] = 0.20; names[1] = "Ballpen"; names[2] = "Notebook"; names[3] = "Envelope"; Quantity[1] = 20; Quantity[2] = 5; Quantity[3] = 140; I enter data to arrays by myself in this case. Now i want to change my code so that my program asks user for names, price and quantity (using the Scanner class). After user enter data, program keep this in three different arrays. I dont know how to transfer data from user to arrays. I would be grateful for some example code or any help.

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  • Whats wrong with this method?

    - by David
    Here's the method: public static String CPUcolor () { System.out.println ("What color am I?") ; String s = getIns() ; System.out.println ("are you sure I'm "+s+"? (Y/N)") ; String a = getIns() ; while (!((a.equals ("y")) || (a.equals ("Y")) || (a.equals ("n")) || (a.equals ("N")))) { System.out.println ("try again") ; a = getIns () ; } if (a.equals ("n") || a.equals("N")) {CPUcolor() ;} System.out.println ("I am "+s) ; return s ; } here is a possible output of this method (y's and n's are user inputs): What color am I? red are you sure I'm red? (Y/N) N What color am I? blue are you sure I'm blue? (Y/N) N What color am I? Yellow are you sure I'm Yellow? (Y/N) y I am Yellow I am blue I am red Why is it that the line's "I am blue" and "I am Blue" printed? Why are they printed in reverse order with red, the first entered, printed last?

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  • Loading data from file to Vector structure

    - by owca
    I'm trying to parse through fixed-width formatted file extracting x,y values of points from it, and then storing them in int[] array inside a Vector. Text file looks as follows : 0006 0015 0125 0047 0250 0131 That's the code : Vector<int[]> vc = new Vector<int[]>(); try { BufferedReader file = new BufferedReader(new FileReader("myfile.txt")); String s; int[] vec = new int[2]; while ((s = file.readLine()) != null) { vec[0] = Integer.parseInt(s.substring(0, 4).trim()); vec[1] = Integer.parseInt(s.substring(5, 8).trim()); vc.add(vec); } file.close(); } catch (IOException e) { } for(int i=0; i<vc.size(); i++){ for(int j=0; j<2; j++){ System.out.println(vc.elementAt(i)[j]); } } But the output shows only last line. 250 131 250 131 250 131 Should I somehow use Vector.nextElement() here to get all my data ?

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  • converting result set to list

    - by akshay
    how can i conver result set to list? i am using following code but its not working properly private List<User> convertToList(ResultSet rs) { List<User> userList = new ArrayList(); User user = new User(); try { while (rs.next()) { user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setFname(rs.getString("fname")); user.setLname(rs.getString("lname")); user.setUsertype(rs.getInt("usertype")); user.setPasswd(rs.getString("passwd")); user.setEmail(rs.getString("email")); userList.add(user); } } catch (SQLException ex) { Logger.getLogger(UserDAO.class.getName()).log(Level.SEVERE, null, ex); } finally { closeConnection(); } return userList; }

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  • Auto injecting logger with guice

    - by koss
    With reference to Guice's custom injections article, its TypeListener performs a check for InjectLogger.class annotation - which can be optional. Removing that check will inject to all Logger.class types. class Log4JTypeListener implements TypeListener { public <T> void hear(TypeLiteral<T> typeLiteral, TypeEncounter<T> typeEncounter) { for (Field field : typeLiteral.getRawType().getDeclaredFields()) { if (field.getType() == Logger.class && field.isAnnotationPresent(InjectLogger.class)) { typeEncounter.register(new Log4JMembersInjector<T>(field)); } } } } I'm tempted to remove "&& field.isAnnotationPresent(InjectLogger.class)" from the listener. If we're using Guice to inject all instances of our Logger, is there any reason not to do it automatically (without need to annotate)?

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  • Mapping enum to a table with hibernate annotation

    - by Thierry-Dimitri Roy
    I have a table DEAL and a table DEAL_TYPE. I would like to map this code: public class Deal { DealType type; } public enum DealType { BASE("Base"), EXTRA("Extra"); } The problem is that the data already exist in the database. And I'm having a hard time mapping the classes to the database. The database looks something like that: TABLE DEAL { Long id; Long typeId; } TABLE DEAL_TYPE { Long id; String text; } I know I could use a simple @OneToMany relationship from deal to deal type, but I would prefer to use an enum. Is this possible? I almost got it working by using a EnumType.ORDINAL type. But unfortunately, my IDs in my deal type table are not sequential, and do not start at 1. Any suggestions?

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  • What is the fastest findByName query with hibernate?

    - by Karussell
    I am sure I can improve the performance of the following findByName query of hibernate: public List<User> findByName(String name) { session.createCriteria(User.class).add(Restrictions.eq("name", name)).list(); } In which way should I improve it or even more important: in which ways should I improve it first? I will need the full object with all the collections (layz or not) and deps of this class.

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  • a problem with JTabedPanel

    - by sirvan
    hi, I have an application that includes an JtabedPanel and two Tabes with some componetnts,my problem is when i click on another Tab,it's components not appeared immediately but when mouse courser move over each component(Jcheckbox,Jbutton and so on) of the tab,the components will appear but not correctly (see below image) This is my CODE . . .

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  • ActiveMq integration with Spring 2.5

    - by Tony
    I am using ActiveMq 5.32 with Spring 2.5.5. I use pretty generic configuration, as long as I include the jmsTransactionManager in DefaultMessageListenerContainer, Spring throw an error on start up: "Error creating bean with name 'org.springframework.jms.listener.DefaultMessageListenerContainer#0'" Without the transactionManager attribute , this works fine, but when I add 10 messages to the message queue, a transaction exception will occur. Part of my configurations : <bean class="org.springframework.jms.listener.DefaultMessageListenerContainer"> <property name="connectionFactory" ref="connectionFactory" /> <property name="destination" ref="emailDestination" /> <property name="messageListener" ref="emailServiceMDP" /> <property name="transactionManager" ref="jmsTransactionManager" /> </bean> <bean id="jmsTransactionManager" class="org.springframework.jms.connection.JmsTransactionManager"> <property name="connectionFactory" ref="connectionFactory" /> </bean> Does this version of Spring and Activemq has some know issues in integration ? Or do I need additional libs to get jmsTransactionManager to work ?

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  • Generate URL for File

    - by Don
    The default output of File.toURL() is file:/c:/foo/bar These don't appear to work on windows, and need to be changed to file:///c:/foo/bar Does the format file:/c:/foo/bar work correctly on Unix (I don't have a Unix machine to test on)? Is there a library that can take care of generating a URL from a File that is in the correct format for the current environment?

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  • Generating different randoms valid for a day on different independent devices?

    - by Pentium10
    Let me describe the system. There are several mobile devices, each independent from each other, and they are generating content for the same record id. I want to avoid generating the same content for the same record on different devices, for this I though I would use a random and make it so too cluster the content pool based on these randoms. Suppose you have choices from 1 to 100. Day 1 Device#1 will choose for the record#33 between 1-10 Device#2 will choose for the record#33 between 40-50 Device#3 will choose for the record#33 between 50-60 Device#1 will choose for the record#55 between 40-50 Device#2 will choose for the record#55 between 1-10 Device#3 will choose for the record#55 between 10-20 Device#1 will choose for the record#11 between 1-10 Device#2 will choose for the record#22 between 1-10 Device#3 will choose for the record#99 between 1-10 Day 2 Device#1 will choose for the record#33 between 90-100 Device#2 will choose for the record#33 between 1-10 Device#3 will choose for the record#33 between 50-60 They don't have access to a central server. Data available for each of them: IMEI (unique per mobile) Date of today (same on all devices) Record id (same on all devices) What do you think, how is it possible? ps. tags can be edited

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  • Transient variables are not captured properly on form submission

    - by Kalpana
    My User entity class have several member variables (e.g. String firstName) which are persisted and some transient variables (e.g. transient boolean selected) which are not. I have used the transient variable to capture a checkbox selection, but invariably the value never gets set and procesed properly until I set another bean value along with it. i.e. If User has firstName (mapped to a text field) and selected (mapped to a checkbox) If I just selected the value doesn't seem to be set on an update If I had selected the checkbox and the firstName field, the "selected" value is captured properly Can anyone tell me why this is happening?

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  • Generics in return types of static methods and inheritance

    - by Axel
    Generics in return types of static methods do not seem to get along well with inheritance. Please take a look at the following code: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { // Error: The return type is incompatible with A.getClassInfo() public static ClassInfo<B> getClassInfo() { return new ClassInfo<B>(B.class, A.getClassInfo()); } } I tried to circumvent this by changing the return type for A.getClassInfo(), and now the error pops up at another location: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<? extends A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { public static ClassInfo<? extends B> getClassInfo() { // Error: The constructor ClassInfo<B>(Class<B>, ClassInfo<capture#1-of ? extends A>) is undefined return new ClassInfo<B>(B.class, A.getClassInfo()); } } What is the reason for this strict checking on static methods? And how can I get along? Changing the method name seems awkward.

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  • any way to use ajax with jstl customtags without duplicating tags in javascript?

    - by CodeMonkeyB
    I am working on a page where part of the content is loaded normally and the pages are rendered using jsps. The product images and links generated on that page are by custom jstl tags. When the user scrolls more products are requested from the server in a JSON response and then using UnderscoreJS templates they are rendered and added to the bottom of the page. Is there any way I can use the JSTL tags in Javascript without recreating them using a javascript function (it won't be possible to re-create all of them in javascript). What is the best way to handle this scenario? I guess I could return a rendered html response for the ajax call, but that would mean I have some ajax requests which use json and some that use rendered html...

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  • Hibernate is performing unwanted SELECTs on call to saveOrUpdate

    - by digiarnie
    Let's say I have a House entity which maps to many Person entities. I then load an existing House which has 20 occupants. beginTransaction(); House house = houseDao.find(1L); commitTransaction(); Later in the code, I can then add a new Person to the House: ... List<Person> people = house.getPeople(); people.add(new Person("Dilbert")); .... When I make the call: session.saveOrUpdate(house); Hibernate performs 21 queries: 1 to SELECT the House and 20 to SELECT each existing Person in the House. I'm sure it's a small issue on my part, however, what should I do so that I can add a new Person to the house without having such a heavy hit on the database in this situation? This is all done within the same session.

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  • can't understand the url function used in the google taskque api documentation

    - by Bunny Rabbit
    import com.google.appengine.api.labs.taskqueue.Queue; import com.google.appengine.api.labs.taskqueue.QueueFactory; import static com.google.appengine.api.labs.taskqueue.TaskOptions.Builder.*; // ... Queue queue = QueueFactory.getDefaultQueue(); queue.add(url("/worker").param("key", key)) in the code example given on the google task queue documentation page i can't understand the url("/worker") function they are calling in the queues.add() invocation .

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  • Problem with ModelAndView and ModelMap in AnnotationController, Springframework

    - by saltfactory
    I have a question that is a point difference between ModelAndView and ModelMap. I want to maintain modelAndView when requestMethod is "GET" and requestMethod is "POST". My modelAndView saved others. So I made modelAndView return type to "GET", "POST" methods. But, Request lost commandObject, form:errors..., if request return showForm on "POST" because request validation failed. example) private ModelAndView modelAndView; public ControllerTest{ this.modelAndView = new ModelAndView(); } @RequestMapping(method = RequestMethod.GET) public ModelAndView showForm(ModelMap model) { EntityObject entityObject = new EntityObject(); CommandObject commandObject = new CommandObject(); commandObject.setEntityObject(entityObject); model.addAttribute("commandObject", commandObject); this.modelAndView.addObject("id", "GET"); this.modelAndView.setViewName("registerForm"); return this.modelAndView; } @RequestMapping(method = RequestMethod.POST) public ModelAndView submit(@ModelAttribute("commandObject") CommandObject commandObject, BindingResult result, SessionStatus status) { this.commandValidator.validate(commandObject, result); if (result.hasErrors()) { this.modelAndView.addObject("id", "POST"); this.modelAndView.setViewName("registerForm"); return this.modelAndView; } else { this.modelAndView.addObject("id", "after POST"); this.modelAndView.setViewName("success"); } status.setComplete(); return this.modelAndView; }

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  • What does plus sign does here in string?

    - by Thanga
    I would like to know, what is the difference between two statements, these may be simple String ss="myname"; char[] charArray = ss.toCharArray(); for ( char character : charArray ) { System.out.println( +character );//Statements are here what does plus refers here: System.out.println( character ); //Statements are here: } I got the output for the code no errors but little doubt on how it works? What happens here? If you would down vote let me know the reason please , Thanks in advance

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  • What do the external JSF libraries/frameworks add?

    - by kgrad
    I have seen mention of a bunch of external JSF Libraries such as ICEfaces, Richfaces, etc. However, I am unsure as to what these libraries actually add over just using JSF 2.0. Are they just additional components that are pre-built? I know that PrettyFaces adds URL rewriting, and I Believe that ICEFaces/Richfaces add Ajax enabled components? What are some other major component libraries, what are their benefits / why should people use them? Additionally, what does a framework like SEAM add over using straight JSF2 with EJB? Is MYFaces simply a different implementation of JSF?

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