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  • What situations does a Monostate pattern model?

    - by devoured elysium
    I know what both a Singleton or a Monostate are and how to implement them. Although I can see many uses for a Singleton, I can't imagine a situation where I would want to let the user create as many instances of my class although in reality only one really exists behind the scenes. Can anybody help me here? I know that for several reasons one should stay away from both patterns, but in theory, what kind of problems does the Monostate model? Thanks

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  • Swing: Scroll to bottom of JScrollPane, conditional on current viewport location

    - by I82Much
    Hi all, I am attempting to mimic the functionality of Adium and most other chat clients I've seen, wherein the scrollbars advance to the bottom when new messages come in, but only if you're already there. In other words, if you've scrolled a few lines up and are reading, when a new message comes in it won't jump your position to the bottom of the screen; that would be annoying. But if you're scrolled to the bottom, the program rightly assumes that you want to see the most recent messages at all times, and so auto-scrolls accordingly. I have had a bear of a time trying to mimic this; the platform seems to fight this behavior at all costs. The best I can do is as follows: In constructor: JTextArea chatArea = new JTextArea(); JScrollPane chatAreaScrollPane = new JScrollPane(chatArea); // We will manually handle advancing chat window DefaultCaret caret = (DefaultCaret) chatArea.getCaret(); caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE); In method that handles new text coming in: boolean atBottom = isViewAtBottom(); // Append the text using styles etc to the chatArea if (atBottom) { scrollViewportToBottom(); } public boolean isAtBottom() { // Is the last line of text the last line of text visible? Adjustable sb = chatAreaScrollPane.getVerticalScrollBar(); int val = sb.getValue(); int lowest = val + sb.getVisibleAmount(); int maxVal = sb.getMaximum(); boolean atBottom = maxVal == lowest; return atBottom; } private void scrollToBottom() { chatArea.setCaretPosition(chatArea.getDocument().getLength()); } Now, this works, but it's janky and not ideal for two reasons. By setting the caret position, whatever selection the user may have in the chat area is erased. I can imagine this would be very irritating if he's attempting to copy/paste. Since the advancement of the scroll pane occurs after the text is inserted, there is a split second where the scrollbar is in the wrong position, and then it visually jumps towards the end. This is not ideal. Before you ask, yes I've read this blog post on Text Area Scrolling, but the default scroll to bottom behavior is not what I want. Other related (but to my mind, not completely helpful in this regard) questions: Setting scroll bar on a jscrollpane Making a JScrollPane automatically scroll all the way down. Any help in this regard would be very much appreciated.

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  • Exception thrown while working with JTabbedPane

    - by Halo
    I'm using a JTabbedPane in my application and I listen to its changes with ChangeListener so that I can know which tab is currently selected. So my stateChanged method is; public void stateChanged(ChangeEvent e) { currentPageIndex = jTabbedPane.getSelectedIndex(); } But while I'm adding new tabs to the JTabbedPane it throws an ArrayIndexOutOfBoundsException in the method above, I don't know why. Some suggested for a similar case that this is a bug http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4873983, but as you'll see some says the solution is to work with Swing from EventDispatchThread. What does it mean, do they mean the SwingUtilities.invokeLater thing? Can someone show me how I can modify my stateChanged method accordingly to avoid the exception?

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  • Best practice for DAO pattern ?

    - by Tony
    I've seen a lot of codes use a service-dao pattern , I don't know the origin of this pattern . It force the front layer call service , then delegates some of the service task to dao. I want to ask : Does DAO layer do purely data access related task ? What about exception encapsulation ? Is there other pattern can be used to replace this ?

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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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  • Finding the order of method calls in Eclipse

    - by Chathuranga Chandrasekara
    Suppose I have a big program that consists of hundreds of methods in it. And according to the nature of input the program flow is getting changed. Think I want to make a change to the original flow. And it is big hassle to find call hierarchy/ references and understand the flow. Do I have any solution for this within Eclipse? Or a plugin? As an example, I just need a Log of method names that is in order of time. Then I don't need to worry about the methods that are not relevant with my "given input" Update : Using debug mode in eclipse or adding print messages are not feasible. The program is sooooo big. :)

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  • Dynamic graphing using Jfreechart

    - by Albinoswordfish
    Right now I'm using JFreeChart in order to create a dynamic chart. However the chart is significantly slowing down my GUI. I was just wondering, is jfreechart generally heavy in the graphics department (my computer is not fast at all). Or is there a way to configure the ChartPanel to better optimize dynamic charting.

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  • JDBC profiling tools

    - by antispam
    We need to profile the JDBC operations of several web applications, number of queries, time spent, rows returned, ... Have you used any free/commercial JDBC profiling tool? What are your experiences? Thank you.

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  • Can someone explain the ivy.xml dependency's conf attribute?

    - by tieTYT
    I can't find any thorough explanation of the ivy dependency tag's conf attribute: <dependency org="hibernate" name="hibernate" rev="3.1.3" conf="runtime, standalone -> runtime(*)"/> See that conf attribute? I can't find any explanation (that I can understand) about the right hand side of the - symbol. PLEASE keep in mind I don't know the first thing about maven so please explain this attribute with that consideration. Yes, I've already looked at this: http://ant.apache.org/ivy/history/latest-release/ivyfile/dependency.html Thanks, Dan

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  • Passing empty list as parameter to JPA query throws error

    - by Tuukka Mustonen
    If I pass an empty list into a JPA query, I get an error. For example: List<Municipality> municipalities = myDao.findAll(); // returns empty list em.createQuery("SELECT p FROM Profile p JOIN p.municipality m WHERE m IN (:municipalities)") .setParameter("municipalities", municipalities) .getResultList(); Because the list is empty, Hibernate generates this in SQL as "IN ()", which gives me error with Hypersonic database. There is a ticket for this in Hibernate issue tracking but there are not many comments/activity there. I don't know about support in other ORM products or in JPA spec either. I don't like the idea of having to manually check for null objects and empty lists every time. Is there some commonly known approach/extension to this? How do you handle these situations?

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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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  • Can any framework project use Struts-taglib

    - by ChronoXIII
    I have read here that one disadvantage that some may find with using Spring MVC over Struts is that Struts has tags that output HTML code, while Spring has tags that don't generate HTML. My question is can't you just use the Struts tag-lib in a Spring MVC project (or any other kind of framework project), by dropping the right jar into the WEB-INF/lib folder? Any clarification is appreciated, thanks.

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  • activate and deactivate ComboBox

    - by Jessy
    How can I make the comboBox available when the checkBox was uncheck (vice versa) Why the comboBox is still disable after I unChecked the checkBox? choice [] = {"A","B","C"}; JComboBox a = new JComboBox(choice); JCheckBox chk = new JCheckBox("choice"); ... a.addActionListener(this); chk.addActionListener(this); ... public void actionPerformed(ActionEvent e) { //disable the a comboBox when the checkBox chk was checked if(e.getSource()==chk) a.setEnabled(false); //enable the a comboBox when the checkBox chk was unchecked else if(e.getSource()!=chk) a.setEnabled(true); }

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  • What's in an Eclipse .classpath/.project file?

    - by totalEclipse
    We recently had an issue with an Eclipse project for one of our team members. Tomcat was not deploying JARs of the application. We eventually noticed the .classpath Eclipse file was not the same as for the team members where the project was OK. We replaced the .classpath file with one from a project that was OK and the Tomcat deploy was complete. Just out of curiosity and to know at what to look in the future if something is wrong, what is inside the .classpath and .project files. What can I add in there, what does it all mean?

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  • Throwing exception vs returning null value with switch statement

    - by Greg
    So I have function that formats a date to coerce to given enum DateType{CURRENT, START, END} what would be the best way to handling return value with cases that use switch statement public static String format(Date date, DateType datetype) { ..validation checks switch(datetype){ case CURRENT:{ return getFormattedDate(date, "yyyy-MM-dd hh:mm:ss"); } ... default:throw new ("Something strange happend"); } } OR throw excpetion at the end public static String format(Date date, DateType datetype) { ..validation checks switch(datetype){ case CURRENT:{ return getFormattedDate(date, "yyyy-MM-dd hh:mm:ss"); } ... } //It will never reach here, just to make compiler happy throw new IllegalArgumentException("Something strange happend"); } OR return null public static String format(Date date, DateType datetype) { ..validation checks switch(datetype){ case CURRENT:{ return getFormattedDate(date, "yyyy-MM-dd hh:mm:ss"); } ... } return null; } What would be the best practice here ? Also all the enum values will be handled in the case statement

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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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  • Converting raw bytes into audio sound

    - by Afro Genius
    In my application I inherit a javastreamingaudio class from the freeTTS package then bypass the write method which sends an array of bytes to the SourceDataLine for audio processing. Instead of writing to the data line, I write this and subsequent byte arrays into a buffer which I then bring into my class and try to process into sound. My application processes sound as arrays of floats so I convert to float and try to process but always get static sound back. I am sure this is the way to go but am missing something along the way. I know that sound is processed as frames and each frame is a group of bytes so in my application I have to process the bytes into frames somehow. Am I looking at this the right way? Thanx in advance for any help.

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  • how to continuously send data without blocking?

    - by Donal Rafferty
    I am trying to send rtp audio data from my Android application. I currently can send 1 RTP packet with the code below and I also have another class that extends Thread that listens to and receives RTP packets. My question is how do I continuously send my updated buffer through the packet payload without blocking the receiving thread? public void run() { isRecording = true; android.os.Process.setThreadPriority (android.os.Process.THREAD_PRIORITY_URGENT_AUDIO); int buffersize = AudioRecord.getMinBufferSize(8000, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT); Log.d("BUFFERSIZE","Buffer size = " + buffersize); arec = new AudioRecord(MediaRecorder.AudioSource.MIC, 8000, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, buffersize); short[] readBuffer = new short[80]; byte[] buffer = new byte[160]; arec.startRecording(); while(arec.getRecordingState() == AudioRecord.RECORDSTATE_RECORDING){ int frames = arec.read(readBuffer, 0, 80); @SuppressWarnings("unused") int lenghtInBytes = codec.encode(readBuffer, 0, buffer, frames); RtpPacket rtpPacket = new RtpPacket(); rtpPacket.setV(2); rtpPacket.setX(0); rtpPacket.setM(0); rtpPacket.setPT(0); rtpPacket.setSSRC(123342345); rtpPacket.setPayload(buffer, 160); try { rtpSession2.sendRtpPacket(rtpPacket); } catch (UnknownHostException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (RtpException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } So when I send on one device and receive on another I get decent audio, but when I send and receive on both I get broken sound like its taking turns to send and receive audio. I have a feeling it could be to do with the while loop? it could be looping around in there and not letting anything else run?

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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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  • custom tag 'cannot be resolved to a type'

    - by lotus99t
    I have a custom tag, packaged into a library jar that is included in my web apps war file. I get the following error: An error occurred at line: 66 in the jsp file: /WEB-INF/jsp/portlet/portfolio/operations/operationsInfo.jsp org.apache.jsp.tag.meta.form.WidgetFactory_tag cannot be resolved to a type 63: <c:forEach var="fldCfg" items="${config.page.fields}" > 64: <tr> 65: <td><form:Label fld="${fldCfg}"/></td> 66: <td><form:WidgetFactory fld="${fldCfg}" decodesMap="${decodesMap}" command="${operationsInfoBean}" dateFormat="${preferredDateFormat}"/></td> 67: </tr> 68: </c:forEach> 69: </table> But it doesn't seem to complain about Label which is in the same taglib. I've confirmed that the jar is in the war and that the tag file is in the jar and the that the TLD (in META-INF) expressly defines 'WidgetFactory' Why am I getting this error?

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  • Reflection: cast an object to subclass without use instaceof

    - by Fabrizio
    I have this simple interface/class: public abstract class Message { } public class Message1 extends Message{ } public class Message2 extends Message{ } And an utility class: public class Utility { public void handler(Message m){ System.out.println("Interface: Message"); } public void handler(Message1 m){ System.out.println("Class: Message1"); } public void handler(Message2 m){ System.out.println("Class: Message2"); } } Now, the main class: public static void main(String[] args) { Utility p=new Utility(); Message1 m1=new Message1(); p.handler(m1); Message m=(Message) m1; p.handler(m); } The output is Class: Message1 Interface: Message I would that p.handler(m) call the method p.handler(m:Message1) I don't want use the "manual" command instanceof because I have many cases: if(m instance of Message1) p.handler((Message1)m) else if (m instanceof Message2) p.handler((Message2)m) ... If I call m.getClass() I obtain "mypackage.Message1", so the subclass and not the superclass. I try with this code (use reflection): p.handler(m.getClass().cast(m)); But the output is Interface: Message So, this is my problem. I would do a runtime cast of superclass object to subclassobject without use the "code command" istanceof. I would a right command like this: p.handler((m.getclass)m); How can I obtain it? It's possible? Thank in advance. Fabrizio

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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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