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  • How convince other developers not to ignore Exceptions?

    - by Mnementh
    Recently I encountered a bug in an application I took over from another developer. I debugged for the reason and over an hour later I realized, that the problem wasn't the code producing the exception, but some code executed before this returning wrong data. If I dived into this, I encountered the following: try { ... } catch (XYException e){} If the Exception would have been propagated (a change I did), I would have found the reason for the bugs in a few minutes, as the stacktrace had pointed me to the problem. So how can I convince other developers to never catch and ignore exceptions in this way?

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  • The fastest way to do a collection subtraction

    - by Tony
    I have two Sets. Set<B> b is the subset of Set<A> a. they're both very huge Sets. I want to subtract b from a , what's the best practice to do this common operation ? I've written to many codes like this , and I don't think it's efficient. what's your idea ? for(int i = 0 ; i < a.size(); i++) { for (int j=0 ; j < b.size() ;j++) { // do comparison , if found equals ,remove from a break; } } And I want to find an algorithm , not only applies to Sets, also works for Array.

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  • JFrame not working correctly

    - by Nick Gibson
    This is making me very angry, I have worked on this for 2 days, have 2 books open and have looked through them, and STILL can't get this program to run the way I want it run. I'm getting to the point where if this doesn't help, I quit. I want a SIMPLE Frame application. It has a JComboBox centered at the top. Next to it is a text field big enough to show numeric digits such as "$49.99" Below it is a spot for a Text area showing terms of service Below that is the checkbox agreeing to the terms of service Below that is 2 buttons "Accept" and "Decline" I Have worked on this for 2 days, here is the coding: public class Bar extends JFrame implements ActionListener { public Bar(final JFrame frame) { String[] tests = { "A+ Certification", "Network+ Certification", "Security+ Certification", "CIT Full Test Package" }; JButton button = new JButton("Click Meh"); add(new JLabel("Welcome to the CIT Test Program ")); add(new JLabel("Please select which Test Package from the list below.")); frame.setVisible(true); frame.setSize(250,250); JPanel pane1 = new JPanel(new FlowLayout()); JPanel pane2 = new JPanel(new FlowLayout()); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); JMenu editMenu = new JMenu("Edit"); JMenu helpMenu = new JMenu("Help"); menuBar.add(fileMenu); menuBar.add(editMenu); menuBar.add(helpMenu); JMenuItem newMenu = new JMenuItem("New (Ctrl+N)"); JMenuItem openMenu = new JMenuItem("Open (Ctrl+O)"); JMenuItem saveMenu = new JMenuItem("Save (Ctrl+S)"); saveMenu.addActionListener(this); JMenuItem exitMenu = new JMenuItem("Exit (Ctrl+W)"); JMenuItem cutMenu = new JMenuItem("Cut (Ctrl+X)"); JMenuItem copyMenu = new JMenuItem("Copy (Ctrl+C)"); JMenuItem pasteMenu = new JMenuItem("Paste (Ctrl+V)"); JMenuItem infoMenu = new JMenuItem("Help (Ctrl+H)"); fileMenu.add(newMenu); fileMenu.add(openMenu); fileMenu.add(saveMenu); fileMenu.add(exitMenu); editMenu.add(cutMenu); editMenu.add(copyMenu); editMenu.add(pasteMenu); helpMenu.add(infoMenu); frame.setJMenuBar(menuBar); JComboBox packageChoice = new JComboBox(tests); frame.add(packageChoice); } public void actionPerformed(ActionEvent e) { Object source = e.getSource(); { } } EDIT: Forgot to add the second program public class JFrameWithPanel { public static void main(String[] args) { JPanel panel = new Bar(new JFrame("CIT Test Program")); } } How do I get this to have everything where I want it and show up? I'm very confused because of this and now barely even get how Frames work.

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  • Is it possible to make web app proactive rather than reactive?

    - by Ari B.
    Web applications traditionally follow the request/response cycle, where a request is made by a user or another web app. However, I'm curious if it is possible to make a web app automatically initiate certain tasks upon it's deployment to a app server. For example, let's say we have a web app that retrieves and processes data. Is it possible to configure this app to automatically retrieve and process data when certain criteria are met, rather than needing a request from a user/another web app?

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  • Hibernate Mapping Annotation Question?

    - by paddydub
    I've just started using hibernate and I'm trying to map walking distance between two coordinates into a hashmap, There can be many connections from one "FromCoordinate" to another "ToCoordinate". I'm not sure if i've implemented this correctly, What annotations do i need to map this MashMap? Thanks @Entity @Table(name = "COORDCONNECTIONS") public class CoordinateConnection implements Serializable{ private static final long serialVersionUID = -1624745319005591573L; /** auto increasing id number */ @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "ID") @id private int id; @Embedded public FromCoordinate fromCoord; @Embedded public ToCoordinate toCoord; HashMap<Coordinate, ArrayList<Coordinate>> coordWalkingConnections = new HashMap<Coordinate, ArrayList<Coordinate>>(); } public class FromCoordinate implements ICoordinate { @Column(name = "FROM_LAT") private double latitude; @Column(name = "FROM_LNG") private double longitude; } public class ToCoordinate implements ICoordinate { @Column(name = "TO_LAT") private double latitude; @Column(name = "TO_LNG") private double longitude; @Column(name = "DISTANCE") private double distance; } DATABASE STRUCTURE id FROM_LAT FROM_LNG TO_LAT TO_LNG Dist 1 43.352669 -6.264341 43.350012 -6.260653 0.38 2 43.352669 -6.264341 43.352669 -6.264341 0.00 3 46.352669 -6.264341 43.353373 -6.262013 0.17 4 47.352465 -6.265865 43.351290 -6.261200 0.25 5 45.452578 -6.265768 43.352788 -6.264396 0.01 6 45.452578 -6.265768 45.782788 -6.234523 0.01 ..... ... . Example HashMap for HashMap<Coordinate, ArrayList<Coordinate>> <KEY{43.352669 -6.264341}, Arraylist VALUES{(43.350012,-6.260653,0.383657), (43.352669, -6.264341, 0.000095), (43.353373, -6.262013, 0.173201)}> <KEY{47.352465 -6.265865}, Arraylist VALUES{(43.351290,-6.261200,0.258781)}> <KEY{45.452578 -6.265768}, Arraylist VALUES{(43.352788,-6.264396,0.013726),(45.782788,-6.234523,0.017726)}>

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  • JPA query for getting the whole tree

    - by Javi
    Hello, I have a class which models all categories and they can be ordered hierarchically. @Entity @Table(name="categories") public class Category { @Id @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="sequence") @SequenceGenerator(name="sequence", sequenceName="categories_pk_seq", allocationSize=1) @Column(name="id") private Long id; @Column private String name; @OneToOne @JoinColumn(name="idfather") private Category father; } I need to get all categories ordered hierarchically (I mean every father followed by its children and fathers ordered alphabetically on each level) as they could be made for example with PRIOR in oracle. Is it possible to do this with a JPA Query (not a SQL one)? Thanks.

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  • Wrong background colors in Swing ListCellRenderer

    - by Johannes Rössel
    I'm currently trying to write a custom ListCellRenderer for a JList. Unfortunately, nearly all examples simply use DefaultListCellRenderer as a JLabel and be done with it; I needed a JPanel, however (since I need to display a little more info than just an icon and one line of text). Now I have a problem with the background colors, specifically with the Nimbus PLAF. Seemingly the background color I get from list.getBackground() is white, but paints as a shade of gray (or blueish gray). Outputting the color I get yields the following: Background color: DerivedColor(color=255,255,255 parent=nimbusLightBackground offsets=0.0,0.0,0.0,0 pColor=255,255,255 However, as can be seen, this isn't what gets painted. It obviously works fine for the selected item. Currently I even have every component I put into the JPanel the cell renderer returns set to opaque and with the correct foreground and background colors—to no avail. Any ideas what I'm doing wrong here? ETA: Example code which hopefully runs. public class ParameterListCellRenderer implements ListCellRenderer { @Override public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) { // some values we need Border border = null; Color foreground, background; if (isSelected) { background = list.getSelectionBackground(); foreground = list.getSelectionForeground(); } else { background = list.getBackground(); foreground = list.getForeground(); } if (cellHasFocus) { if (isSelected) { border = UIManager.getBorder("List.focusSelectedCellHighlightBorder"); } if (border == null) { border = UIManager.getBorder("List.focusCellHighlightBorder"); } } else { border = UIManager.getBorder("List.cellNoFocusBorder"); } System.out.println("Background color: " + background.toString()); JPanel outerPanel = new JPanel(new BorderLayout()); setProperties(outerPanel, foreground, background); outerPanel.setBorder(border); JLabel nameLabel = new JLabel("Factory name here"); setProperties(nameLabel, foreground, background); outerPanel.add(nameLabel, BorderLayout.PAGE_START); Box innerPanel = new Box(BoxLayout.PAGE_AXIS); setProperties(innerPanel, foreground, background); innerPanel.setAlignmentX(Box.LEFT_ALIGNMENT); innerPanel.setBorder(BorderFactory.createEmptyBorder(0, 10, 0, 0)); JLabel label = new JLabel("param: value"); label.setFont(label.getFont().deriveFont( AffineTransform.getScaleInstance(0.95, 0.95))); setProperties(label, foreground, background); innerPanel.add(label); outerPanel.add(innerPanel, BorderLayout.CENTER); return outerPanel; } private void setProperties(JComponent component, Color foreground, Color background) { component.setOpaque(true); component.setForeground(foreground); component.setBackground(background); } } The weird thing is, if I do if (isSelected) { background = new Color(list.getSelectionBackground().getRGB()); foreground = new Color(list.getSelectionForeground().getRGB()); } else { background = new Color(list.getBackground().getRGB()); foreground = new Color(list.getForeground().getRGB()); } it magically works. So maybe the DerivedColor with nimbusLightBackground I'm getting there may have trouble?

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  • Hibernate save() and transaction rollback

    - by Marco
    Hi, In Hibernate when i save() an object in a transaction, and then i rollback it, the saved object still remains in the DB. It's strange because this issue doesn't happen with the update() or delete() method, just with save(). Here is the code i'm using: DbEntity dbEntity = getDbEntity(); HibernateUtil.beginTransaction(); Session session = HibernateUtil.getCurrentSession(); session.save(dbEntity); HibernateUtil.rollbackTransaction(); And here is the HibernateUtil class (just the involved functions, i guarantee the getSessionFactory() method works well - there is an Interceptor handler, but it doesn't matter now): private static final ThreadLocal<Session> threadSession = new ThreadLocal<Session>(); private static final ThreadLocal<Transaction> threadTransaction = new ThreadLocal<Transaction>(); /** * Retrieves the current Session local to the thread. * <p/> * If no Session is open, opens a new Session for the running thread. * * @return Session */ public static Session getCurrentSession() throws HibernateException { Session s = (Session) threadSession.get(); try { if (s == null) { log.debug("Opening new Session for this thread."); if (getInterceptor() != null) { log.debug("Using interceptor: " + getInterceptor().getClass()); s = getSessionFactory().openSession(getInterceptor()); } else { s = getSessionFactory().openSession(); } threadSession.set(s); } } catch (HibernateException ex) { throw new HibernateException(ex); } return s; } /** * Start a new database transaction. */ public static void beginTransaction() throws HibernateException { Transaction tx = (Transaction) threadTransaction.get(); try { if (tx == null) { log.debug("Starting new database transaction in this thread."); tx = getCurrentSession().beginTransaction(); threadTransaction.set(tx); } } catch (HibernateException ex) { throw new HibernateException(ex); } } /** * Rollback the database transaction. */ public static void rollbackTransaction() throws HibernateException { Transaction tx = (Transaction) threadTransaction.get(); try { threadTransaction.set(null); if ( tx != null && !tx.wasCommitted() && !tx.wasRolledBack() ) { log.debug("Tyring to rollback database transaction of this thread."); tx.rollback(); } } catch (HibernateException ex) { throw new HibernateException(ex); } finally { closeSession(); } } Thanks

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  • Confused about Huffman Trees

    - by ShrimpCrackers
    A quick tutorial on generating a huffman tree Confused about Huffman Trees. Near the end of that link above, it shows the tree with 2 elements left, and then the completed tree. I'm confused about the way that it is branched. Is there a specific way a huffman tree needs to be branched? For example, 57:* with its right child 35:* is branched off to the right. Could it have been 35 branched to the left with 22 branched to the right? Also, why wasn't 22:* paired up with 15:4 - it just paired with 20:5 to create a new tree. From initial obersvations it seems the tree does not need to be balanced or have any specific order other than that the frequencies of a leaf add up to the value of the parent node. Could two people creating a huffman tree with the same data end up with different encoding values?

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  • Selenium WebDriver Element

    - by cxyz
    How do i configure selenium WebDriver.I have automated test cases using Selenium.Now i need to automate upload and download of a file.So i have to automate using WebDriver.I had added webdriver-common-0.9.7376.jar.Now how do i instantiate for Internet Explorer? Am just decalring variable and using driver private static WebDriver driver; driver.findElement(By.id(upload)).sendKeys("file to be upload"); Is this correct?

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  • Spring/Hibernate/Junit example of testing DAO against HSQLDB

    - by Ryan P.
    Hi guys, I'm working on trying to implement a JUnit test to check the functionality of a DAO. (The DAO will create/read a basic object/table relationship in HSQLDB). The trouble I'm having is the persistence of the DAO (for the non-test code) is being completed through an in-house solution using Spring/Hibernate, which eliminates the usual *.hbm.xml templates that most examples I have found contain. Beacuse of this, I'm having some trouble understanding how to setup a JUnit test to implement the DAO to create/read (just very basic funtionality) to an in-memory HSQLDB. I have found a few examples, but the usage of the in-house persistence means I can't extend some of the classes the examples show (I can't seem to get the application-context.xml setup properly). Can anyone suggest any projects/examples I could take a look at (or any documentation) to further my understanding of the best way to implement this test functionality? I feel like this should be really simple, but I keep running into problems implementing the examples I have found. Thanks in advance!

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  • Freemarker - lack of special character in email subject template cause email content crash

    - by freakman
    im fighting with strange error. Im using seperate freemarker templates for mail subject and body. It is sent using org.springframework.mail.javamail.JavaMailSender. Only templates that contains some special swedish character works in my application ( yes you read right... not the other way). If I delete it my email content crashes. It contains then: MIME-Version: 1.0 Content-Type: text/html;charset=UTF-8 Content-Transfer-Encoding: 7bit .. html code here .. My freemarker.properties file locale=sv_SE classic_compatible=false number_format= date_format=yyyy-MM-dd time_format=HH:mm datetime_format=yyyy-MM-dd HH:mm output_encoding=UTF-8 url_escaping_charset=UTF-8 auto_import=spring.ftl as spring auto_include= default_encoding=UTF-8 localized_lookup=true strict_syntax=true whitespace_stripping=true template_update_delay=10 Ive tried to convert subject file with dos2unix tool. Using 'find -bi subject.ftl' show that encoding is us-ascii. With added special character - utf-8. This thing is suprisingly strange for me... //SOLUTION: use :set bomb and save file in vim.

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  • Why empty String is treated as null in oracle?

    - by GK
    We are using empty string in DB2 database for some business logic. but when the same record tried to insert into the Oracle it throws some not null property references to null value error. that is oracle treats empty string as null. So i am wondering why it is like that. and if there is a requirement of storing empty string how to do that on oracle?

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  • Infinispan equivalent to ehcache's copyOnRead and copyOnWrite

    - by waxwing
    Hi, I am planning to implement a cache solution into an existing web app. Nothing complicated: basically a concurrent map that supports overflowing to disk and automatic eviction. Clustering the cache could be requirement in the future, but not now. I like ehcache's copyOnRead and copyOnWrite features, because it means that I don't have to manually clone things before modifying something I take out of the cache. Now I have started to look at Infinispan, but I have not found anything equivalent there. Does it exist? I.e., the following unit tests should pass: @Test public void testCopyOnWrite() { Date date = new Date(0); cache.put(0, date); date.setTime(1000); date = cache.get(0); assertEquals(0, date.getTime()); } @Test public void testCopyOnRead() { Date date = new Date(0); cache.put(0, date); assertNotSame(cache.get(0), cache.get(0)); }

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  • Is selling a "website screen scraper" is illegal?

    - by Yatendra Goel
    I have coded a "website screen scraper" and want to sell it commercially. I know that webpages scraped by the screen scraper are restricted to be scraped by the webmaser of that website. The robots.txt file of the website says that its webpages must not be scraped. So my question is whether selling that screen scraper is a crime or using that screen scraper is a crime in legal terms. I know that this question is related to law but I thought the software experts on SO must also have answer to this question.

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  • JavaFX: Update of ListView if an element of ObservableList changes

    - by user1828169
    I would like to display a list of persons (coded in POJOS, and containing a name and surname property) using a JavaFX ListView control. I created the ListView and added the list of persons as an ObservableList. Everything works fine if I delete or add a new person to the ObservableList, but changes in the POJO do not trigger an update of the ListView. I have to remove and add the modified POJO from the ObservableList to trigger the update of the ListView. Is there any possibility to display changes in POJOS without the workaround described above?

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  • method names with fluent interface

    - by deamon
    I have a Permissions class with methods in fluent style like this: somePermissions.setRead(true).setWrite(false).setExecute(true) The question is, whether I should name these methods set{Property} or only {property}. The latter would look like this: somePermissions.read(true).write(false).execute(true) If I look at these methods separately I would expect that read reads something, but on the other hand it is closer to the intention to have something like named paramaters like in Scala: Permission(read=true, write=false, execute=true)

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