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  • Is it a bad idea if equals(null) throws NullPointerException instead?

    - by polygenelubricants
    The contract of equals with regards to null, is as follows: For any non-null reference value x, x.equals(null) should return false. This is rather peculiar, because if o1 != null and o2 == null, then we have: o1.equals(o2) // returns false o2.equals(o1) // throws NullPointerException The fact that o2.equals(o1) throws NullPointerException is a good thing, because it alerts us of programmer error. And yet, that error would not be catched if for various reasons we just switched it around to o1.equals(o2), which would just "silently fail" instead. So the questions are: Why is it a good idea that o1.equals(o2) should return false instead of throwing NullPointerException? Would it be a bad idea if wherever possible we rewrite the contract so that anyObject.equals(null) always throw NullPointerException instead?

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  • Eclipse Intro / Welcome page

    - by Raven
    Hello, is it possible to have links on the welcome page which point to defined commands and for example, launch an dialog? I am thinking of having a welcome page, pointing out the steps what to do first, like: 1) change language (click here) 2) set up database connection (click here) 3) start working (click here) "click here" should be a link to call the actual dialog to set things up. I am using Eclipse with the command style menu. Grateful for any suggestions!

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  • print a linear linked list into a table

    - by user1796970
    I am attempting to print some values i have stored into a LLL into a readable table. The data i have stored is the following : DEBBIE STARR F 3 W 1000.00 JOAN JACOBUS F 9 W 925.00 DAVID RENN M 3 H 4.75 ALBERT CAHANA M 3 H 18.75 DOUGLAS SHEER M 5 W 250.00 SHARI BUCHMAN F 9 W 325.00 SARA JONES F 1 H 7.50 RICKY MOFSEN M 6 H 12.50 JEAN BRENNAN F 6 H 5.40 JAMIE MICHAELS F 8 W 150.00 i have stored each firstname, lastname, gender, tenure, payrate, and salary into their own List. And would like to be able to print them out in the same format that they are viewed on the text file i read them in from. i have messed around with a few methods that allow me to traverse and print the Lists, but i end up with ugly output. . . here is my code for the storage of the text file and the format i would like to print out: public class Payroll { private LineWriter lw; private ObjectList output; ListNode input; private ObjectList firstname, lastname, gender, tenure, rate, salary; public Payroll(LineWriter lw) { this.lw = lw; this.firstname = new ObjectList(); this.lastname = new ObjectList(); this.gender = new ObjectList(); this.tenure = new ObjectList(); this.rate = new ObjectList(); this.salary = new ObjectList(); this.output = new ObjectList(); this.input = new ListNode(); } public void readfile() { File file = new File("payfile.txt"); try{ Scanner scanner = new Scanner(file); while(scanner.hasNextLine()) { String line = scanner.nextLine(); Scanner lineScanner = new Scanner(line); lineScanner.useDelimiter("\\s+"); while(lineScanner.hasNext()) { firstname.insert1(lineScanner.next()); lastname.insert1(lineScanner.next()); gender.insert1(lineScanner.next()); tenure.insert1(lineScanner.next()); rate.insert1(lineScanner.next()); salary.insert1(lineScanner.next()); } } }catch(FileNotFoundException e) {e.printStackTrace();} } public void printer(LineWriter lw) { String msg = " FirstName " + " LastName " + " Gender " + " Tenure " + " Pay Rate " + " Salary "; output.insert1(msg); System.out.println(output.getFirst()); System.out.println(" " + firstname.getFirst() + " " + lastname.getFirst() + "\t" + gender.getFirst() + "\t" + tenure.getFirst() + "\t" + rate.getFirst() + "\t" + salary.getFirst()); } }

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  • Is it possible to override the default logging for Glassfish v3?

    - by kgrad
    Related to this question. It appears that Glassfish is exporting slf4j into my application and overriding my logging solution. Is it possible for me to override Glassfish's logging and have my own logging solution take precedence? After searching, I have only found ways to modify the log using logging.properties. I am not married to my current implementation, but I am interested in making it work. thanks.

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  • Update n number of records using JPA with Optimistic locking

    - by Jacques René Mesrine
    I have a table with a column called "count" and I want to run a cron job that will trigger a statement that performs a SQL like this: update summaryTable set count=4; Note that there might be concurrent threads reading & changing the value for "count" when this cron job is triggered. The table has a version column to support Optimistic Locking. What's an efficient way to update the count in JPA ?

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  • Why does Android's onItemClick want a long for row Id?

    - by HenryAdamsJr
    For a listView, when you register an OnItemClickListener, the method you specify looks like this: public abstract void onItemClick (AdapterView parent, View view, int position, long id) The id corresponds to the row that the user clicked on. My question is simply why is it a long and not an int? When would you use it as a long? I've been casting it to an int when I use it, so it makes me think that maybe I'm using it wrong.

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  • Data Structure Behind Amazon S3s Keys (Filtering Data Structure)

    - by dimo414
    I'd like to implement a data structure similar to the lookup functionality of Amazon S3. For those of you who don't know what I'm taking about, Amazon S3 stores all files at the root, but allows you to look up groups of files by common prefixes in their names, therefore replicating the power of a directory tree without the complexity of it. The catch is, both lookup and filter operations are O(1) (or close enough that even on very large buckets - S3's disk equivalents - both operations might as well be O(1))). So in short, I'm looking for a data structure that functions like a hash map, with the added benefit of efficient (at the very least not O(n)) filtering. The best I can come up with is extending HashMap so that it also contains a (sorted) list of contents, and doing a binary search for the range that matches the prefix, and returning that set. This seems slow to me, but I can't think of any other way to do it. Does anyone know either how Amazon does it, or a better way to implement this data structure?

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  • When the request xml with extra elements, return Unmarshalling Error in CXF 2.2.7

    - by yunchat
    The wsdl as following: <xs:complexType name="GetCompositionDto" <xs:complexContent <xs:extension base="tns:baseDto" <xs:sequence <xs:element minOccurs="0" name="itemCode" type="xs:string"/ <xs:element minOccurs="0" name="compositionVersion" type="xs:string"/ </xs:sequence </xs:extension </xs:complexContent </xs:complexType After I updated the CXF the jars. from cxf-2.1.4, jaxb-Impl-2.1.9, jaxb-xjc-2.1.9 To cxf-2.2.7, jaxb-Impl-2.1.12, jaxb-xjc-2.1.12. When I request the XML with following: <itemCodeaa</itemCode <compositionVersionbb</compositionVersion <h22</h --- extra element Displays Errors: Unmarshalling Error: unexpected element (uri:"", local:"h"). Expected elements are <{}itemCode,<{}compositionVersion I know the 'h' doesn't map the element in WSDL. But It's OK in the cxf-2.1.4 version. How can i solve this problem? thanks.

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  • Why declare "private List contactInfos" without a generic ("private List <ContactInfo> contactInfos"

    - by g_imp
    In this example from the App Engine docs, why does the example declare contactInfos like this (no Generics): import javax.jdo.annotations.Element; // ... @Persistent @Element(dependent = "true") private List contactInfos; instead of like this, using a Generic: import javax.jdo.annotations.Element; // ... @Persistent @Element(dependent = "true") private List <ContactInfo> contactInfos;

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  • How to setup an Eclipse Project with multiple Subprojects (OSGi-Bundles)

    - by stacker
    Sherlog is an OSGi-based log analyzer, if I import this project as an workspace snapshot I receive lot's of projects in my workspace, but I would prefere to have them as subprojects in a project. The other option would be to checkout from svn, but then I face other problems (I don't know how to setup the dependencies for automatically build) Does anyone have an idea or good links on this topic? Thanks

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  • POI performance

    - by The Machine
    I am using POI in my J2EE web application to generate a workbook. However, i find that POI takes around 3 mins to create a workbook with 25K rows(with around 15 columns each). Is this a POI performance issue , or is it justified to take that much of time? Are there other APIs known for better performance ?

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  • How To Run integrational Tests

    - by Vladimir
    In our project we have a plenty of Unit Tests. They help to keep project rather well-tested. Besides them we have a set of tests which are unit tests, but depends on some kind of external resource. We call them external tests. They can access web-service sometimes or similar. While unit tests is easy to run the integrational tests couldn't pass sometimes - for example due to timeout error. Also these tests can take too much time to run. Currently we keep integration/external unit tests just to run them when developing corresponding functionality. For plain unit tests we use TeamCIty for continuous integration. How do you run the integration unit tests and when do you run them?

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  • Form input validation with JAX-RS

    - by deamon
    I want to use JAX-RS REST services as a back-end for a web application used directly by humans with browsers. Since humans make mistakes from time to time I want to validate the form input and redisplay the form with validation message, if something wrong was entered. By default JAX-RS sends a 400 or 404 status code if not all or wrong values were send. Say for example the user entered a "xyz" in the form field "count": @POST public void create(@FormParam("count") int count) { ... } JAX-RS could not convert "xyz" to int and returns "400 Bad Request". How can I tell the user that he entered an illegal value into the field "count"? Is there something more convenient than using Strings everywhere and perform conversation by hand?

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  • how to stop directory structure from being viewable in J2EE apps

    - by Omnipresent
    in a J2EE app if user explicitly takes out the the ending page name then what is the best way to not show the directory structure? Example: /mycoolapp/somefolder/test.jsp /mycoolapp/somefolder/ -- this will show all the files under 'somefolder' What is the best way to redirect or show the user a page saying 'not where you belong'. I want to avoid providing index.jsp in all the folders/subfolders of my application. Appserver being used is GlassFish. Also the app is using Struts2 framework, though not all of the code is in struts2. Some code is using traditional Servlets

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  • Stack and Hash joint

    - by Alexandru
    I'm trying to write a data structure which is a combination of Stack and HashSet with fast push/pop/membership (I'm looking for constant time operations). Think of Python's OrderedDict. I tried a few things and I came up with the following code: HashInt and SetInt. I need to add some documentation to the source, but basically I use a hash with linear probing to store indices in a vector of the keys. Since linear probing always puts the last element at the end of a continuous range of already filled cells, pop() can be implemented very easy without a sophisticated remove operation. I have the following problems: the data structure consumes a lot of memory (some improvement is obvious: stackKeys is larger than needed). some operations are slower than if I have used fastutil (eg: pop(), even push() in some scenarios). I tried rewriting the classes using fastutil and trove4j, but the overall speed of my application halved. What performance improvements would you suggest for my code? What open-source library/code do you know that I can try?

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  • how to deploy to remote server with tomcat7-maven-plugin

    - by Msaleh
    i want to use tomcat7-maven-plugin to deploy war file from my local machine to remote server, here's the configuration i have so far: <plugin> <groupId>org.apache.tomcat.maven</groupId> <artifactId>tomcat7-maven-plugin</artifactId> <version>2.0-beta-1</version> <configuration> <server>pb</server> <url>http://mydomain.com:8080/manager/html</url> </configuration> </plugin> do i need more configuration ? and what command do i use to deploy ?

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  • Asynchronous Processing = Spanning Threads = Valid?

    - by jens
    Hello Experts, am I allowed (without any sideeffects) to create and start a new Thread() from within a doGet() Method of a servlet? Or does this somehow leak ressources? Is it valid to also pass the "Session" Object into the Thread to later save the result of my asynchronous processing (I will synchronized correctly) in the session? Or will this leak ressources when using the session "in indepedant threads"? = What would happen if the session meanwhile would be expired by the webcontainer as it has timedout and I will access it from my thread? Or would could this also lead to the sideffect, that storing the session in the thread will prevent the webcontainer from expiring the session at all (and therefore finally leak ressources as the sessions do not get cleared up)? (I know there are other Solutions, like working with DB-(Job)Records, JMS or Servlets 3.0) but I need so solve the problem as described by spanning a new Thread within doGet.) Thank you very much!! Jens

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  • Mock versus Implementation. How to share both approaches in a single Test class ?

    - by Arthur Ronald F D Garcia
    Hi, See the following Mock Test by using Spring/Spring-MVC public class OrderTest { // SimpleFormController private OrderController controller; private OrderService service; private MockHttpServletRequest request; @BeforeMethod public void setUp() { request = new MockHttpServletRequest(); request.setMethod("POST"); Integer orderNumber = 421; Order order = new Order(orderNumber); // Set up a Mock service service = createMock(OrderService.class); service.save(order); replay(service); controller = new OrderController(); controller.setService(service); controller.setValidator(new OrderValidator()); request.addParameter("orderNumber", String.valueOf(orderNumber)); } @Test public void successSave() { controller.handleRequest(request, new MockHttpServletResponse()); // Our OrderService has been called by our controller verify(service); } @Test public void failureSave() { // Ops... our orderNumber is required request.removeAllParameters(); ModelAndView mav = controller.handleRequest(request, new MockHttpServletResponse()); BindingResult bindException = (BindingResult) mav.getModel().get(BindingResult.MODEL_KEY_PREFIX + "command"); assertEquals("Our Validator has thrown one FieldError", bindException.getAllErrors(), 1); } } As you can see, i do as proposed by Triple A pattern Arrange (setUp method) Act (controller.handleRequest) Assert (verify and assertEquals) But i would like to test both Mock and Implementation class (OrderService) by using this single Test class. So in order to retrieve my Implementation, i re-write my class as follows @ContextConfiguration(locations="/app.xml") public class OrderTest extends AbstractTestNGSpringContextTests { } So how should i write my single test to Arrange both Mock and Implementation OrderService without change my Test method (sucessSave and failureSave) I am using TestNG, but you can show in JUnit if you want regards,

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  • Should I use Vaadin Framework

    - by Maksim
    I just tried to play with Vaadin Framework and it seems to me very easy to use. Plus what I like about his framework is that it is built on top of GWT. What do you think, should I continue using this framework or it's better to stick with GWT.

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  • Project in Eclipse that builds a jar used by another project in Eclipse

    - by Paul Tomblin
    I have several projects open in Eclipse. One of them is the main app, and others build jars used by that main app. How do I make it so that when I hit F3 on a method call in the main app that it takes me to the source in the other project instead of taking me to the class file in the Libraries list? I got it so that it shows me the source, but I can't actually edit it like it could if I go to the other project, and similarly when I step through in the debugger it doesn't go into the editable code. I don't know if it's relevant, but we're using Maven to handle the dependencies. I know this should be simple, but I haven't found the option.

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