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  • Is it possible to apply inheritance to a Singleton class?

    - by Bragaadeesh
    Hi, Today I faced one question in interview. Is it possible to apply inheritance concept on Singleton Classes. I said since the constructor is private, we cannot extend that Singleton class (can someone please validate this). Next thing he asked me is to apply inheritance on that Singleton class. So, I made the Singleton's constructor as protected thinking that child's constructor also has be protected. But I was wrong the child can have a modifier either equal to or higher than that. So, I asked him to give a real world example on such a case. He was not able to give me one and said that I cant ask questions and wanted me to tell whether this scenario is possible or not. I went kind of blank. My question here is, Is this possible? Even if its possible, what is the use of it? What real world scenario would demand such a use. Thanks

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  • Is it possible to optimize maven dependencies automatically?

    - by AlexR
    I am working on a big project that consists of about 40 sub-projects with very not optimized dependencies. There are declared dependencies that are not in use as well as used but undeclared dependencies. The second case is possible when dependency is added via other dependency. I want to remove redundant and add required dependencies. I ran mvn dependency:analyze and got a long list of warnings I have to fix now. I wonder whether there is maven plugin or any other utility that can update my pom.xml files automatically. I tried to do it manually but it takes a lot of time. It seems it will take a couple of days of copy/paste to complete the task. In worse case I can write such script myself but probably ready stuff exists? Here is how mvn dependency:analyze reports dependency warnings: [WARNING] Used undeclared dependencies found: [WARNING] org.apache.httpcomponents:httpcore:jar:4.1:compile [WARNING] Unused declared dependencies found: [WARNING] commons-lang:commons-lang:jar:2.4:compile [WARNING] org.json:json:jar:20090211:compile

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  • In ArrayBlockingQueue, why copy final member 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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  • Refactoring a long method that simply populates

    - by Jeune
    I am refactoring a method which is over 500 lines (don't ask me why) The method basically queries a list of maps from the database and for each map in the list does some computation and adds the value of that computation to the map. There are however too many computations and puts being done that the code has reached over 500 lines already! Here's a sample preview: public List<Hashmap> getProductData(...) { List<Hashmap> products = productsDao.getProductData(...); for (Product product: products) { product.put("Volume",new BigDecimanl(product.get("Height")* product.get("Width")*product.get("Length")); if (some condition here) { //20 lines worth of product.put(..,..) } else { //20 lines worth of product.put(..,..) } //3 more if-else statements like the one above try { product.put(..,..) } catch (Exception e) { product.put("",..) } //over 8 more try-catches of the form above } Any ideas on how to go about refactoring this?

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  • Why isn't the @Deprecated annotation triggering a compiler warning about a method?

    - by Scooter
    I am trying to use the @Deprecated annotation. The @Deprecated documentation says that: "Compilers warn when a deprecated program element is used or overridden in non-deprecated code". I would think this should trigger it, but it did not. javac version 1.7.0_09 and compiled using and not using -Xlint and -deprecation. public class test_annotations { public static void main(String[] args) { test_annotations theApp = new test_annotations(); theApp.this_is_deprecated(); } @Deprecated public void this_is_deprecated() { System.out.println("doing it the old way"); } }

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  • Singletons vs. Application Context in Android?

    - by mschonaker
    Recalling this post enumerating several problems of using singletons and having seen several examples of Android applications using singleton pattern, I wonder if it's a good idea to use Singletons instead of single instances shared through global application state (subclassing android.os.Application and obtaining it through context.getApplication()). What advantages/drawbacks would have both mechanisms? To be honest, I expect the same answer in this post http://stackoverflow.com/questions/2709071/singleton-pattern-with-web-application-not-a-good-idea but applied to Android. Am I correct? What's different in DalvikVM otherwise? EDIT: I would like to have opinions on several aspects involved: Synchronization Reusability Testing Thanks in advance.

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  • Android: sending xml as document object, POST method

    - by juro
    i am new at programming and i need some help with that please =/ web service is already written but not by me. so all i have to do is send xml as document object by post method through web service. my code: public class send extends application { @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost("http://app.local/test/"); try { DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder(); Document document = documentBuilder.newDocument(); Element rootElement = document.createElement("packet"); rootElement.setAttribute("version", "1.2"); document.appendChild(rootElement); Element em = document.createElement("imei"); em.appendChild(document.createTextNode("000000000000000")); rootElement.appendChild(em); em = document.createElement("username"); em.appendChild(document.createTextNode("5555")); rootElement.appendChild(em); HttpResponse response = httpclient.execute(httppost); } catch (Exception e) { System.out.println("XML Pasing Excpetion = " + e); } } }

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  • Changing the icon of a .JAR file

    - by Demonick
    How can I change the icon of a .JAR file I want to distribute? I have changed the icon that shows when the program is run, but I want to change the icon in the environment (e.g. Windows XP), that is for the file itself. I googled, but the best I could find is converting the .JAR to a .EXE, which is not the best choice.

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  • How to amend return value design in OO manner?

    - by FrontierPsycho
    Hello. I am no newb on OO programming, but I am faced with a puzzling situation. I have been given a program to work on and extend, but the previous developers didn't seem that comfortable with OO, it seems they either had a C background or an unclear understanding of OO. Now, I don't suggest I am a better developer, I just think that I can spot some common OO errors. The difficult task is how to amend them. In my case, I see a lot of this: if (ret == 1) { out.print("yadda yadda"); } else if (ret == 2) { out.print("yadda yadda"); } else if (ret == 3) { out.print("yadda yadda"); } else if (ret == 0) { out.print("yadda yadda"); } else if (ret == 5) { out.print("yadda yadda"); } else if (ret == 6) { out.print("yadda yadda"); } else if (ret == 7) { out.print("yadda yadda"); } ret is a value returned by a function, in which all Exceptions are swallowed, and in the catch blocks, the above values are returned explicitly. Oftentimes, the Exceptions are simply swallowed, with empty catch blocks. It's obvious that swalllowing exceptions is wrong OO design. My question concerns the use of return values. I believe that too is wrong, however I think that using Exceptions for control flow is equally wrong, and I can't think of anything to replace the above in a correct, OO manner. Your input, please?

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  • Can I mix declarative and programmatic layout in GWT 2.0?

    - by stuff22
    I'm trying to redo an existing panel that I made before GWT 2.0 was released. The panel has a few text fields and a scrollable panel below in a VerticalPanel. What I'd like to do is to make the scrollable panel with UIBinder and then add that to a VerticalPanel Below is an example I created to illustrate this: public class ScrollTablePanel extends ResizeComposite{ interface Binder extends UiBinder<Widget, ScrollTablePanel > { } private static Binder uiBinder = GWT.create(Binder.class); @UiField FlexTable table1; @UiField FlexTable table2; public Test2() { initWidget(uiBinder.createAndBindUi(this)); table1.setText(0, 0, "testing 1"); table1.setText(0, 1, "testing 2"); table1.setText(0, 2, "testing 3"); table2.setText(0, 0, "testing 1"); table2.setText(0, 1, "testing 2"); table2.setText(0, 2, "testing 3"); table2.setText(1, 0, "testing 4"); table2.setText(1, 1, "testing 5"); table2.setText(1, 2, "testing 6"); } } then the xml: <ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder' xmlns:g='urn:import:com.google.gwt.user.client.ui' xmlns:mail='urn:import:com.test.scrollpaneltest'> <g:DockLayoutPanel unit='EM'> <g:north size="2"> <g:FlexTable ui:field="table1"></g:FlexTable> </g:north> <g:center> <g:ScrollPanel> <g:FlexTable ui:field="table2"></g:FlexTable> </g:ScrollPanel> </g:center> </g:DockLayoutPanel> </ui:UiBinder> Then do something like this in the EntryPoint: public void onModuleLoad() { VerticalPanel vp = new VerticalPanel(); vp.add(new ScrollTablePanel()); vp.add(new Label("dummy label text")); vp.setWidth("100%"); RootLayoutPanel.get().add(vp); } But when I add the ScrollTablePanel to the VerticalPanel, only the first FlexTable (test1) is visible on the page, not the whole ScrollTablePanel. Is there a way to make this work where it is possible to mix declarative and programmatic layout in GWT 2.0?

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  • How to convert a BufferedImage to 8 bit?

    - by Zach Sugano
    I was looking at the ImageConverter class, trying to figure out how to convert a BufferedImage to 8-bit color, but I have no idea how I would do this. I was also searching around the internet and I could find no simple answer, they were all talking about 8 bit grayscale images. I simply want to convert the colors of an image to 8 bit... nothing else, no resizing no nothing. Does anyone mind telling me how to do this.

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  • Passing information between test methods in a junit testcase

    - by Jijoy
    Hi, Currently I am creating a TestCase for one work flow and a workflow have different steps. The results of one step is important since , second step needs to know value of step1's execution. class TestCaseWorkFlow1 extends TestCase { private static String resultOfStep1 = null; public void testStep1(){ if(failed){ resultOfStep1 = "failed"; } } public void testStep2(){ if(resultOfStep1 != null ) { //First test failed. }else { } } } Currently we are using static variable to pass information between testmethods . What is the best solution for this scenario ? Please help. Thanks J

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  • Changing order of locations on classpath to be leaded by surefire-plugin

    - by lisak
    Hey folks, does anybody know how to change it ? I mean from target/test-classes ... target/classes .... maven dependencies to target/test-classes ... maven dependencies .... target/classes It relates to this surefire-plugin feature request It's because surefire-plugin cannot exclude resources from /target/classes ... it can only modify resources via <testResources> element that modifies /target/test-classes

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  • How to listen to JComboBox's width changes?

    - by agnieszka
    I tried PropertyChangeListener with property set to "width", "Width", "size" and "Size". PropertyChangeListener widthChangeListener = new PropertyChangeListener() { @Override public void propertyChange(PropertyChangeEvent evt) { //code } }; streamsComboBox.addPropertyChangeListener("width", widthChangeListener); projectsComboBox.addPropertyChangeListener("width", widthChangeListener); vobsComboBox.addPropertyChangeListener("width", widthChangeListener); Nothing works - the handler method is never fired. What should I do to handle JComboBox's size change? Where does the property name come from anyway?

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