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  • Find location using only distance and range?

    - by pinnacler
    Triangulation works by checking your angle to three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and it's to my right at 90 degrees." Repeat 2 more times for different targets and angles. Trilateration works by checking your distance from three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and I'm 100 meters away from that." Repeat 2 more times for different targets and ranges. But both of those methods rely on knowing WHAT you're looking at. Say you're in a forest and you can't differentiate between trees, but you know where key trees are. These trees have been hand picked as "landmarks." You have a robot moving through that forest slowly. Do you know of any ways to determine location based solely off of angle and range, exploiting geometry between landmarks? Note, you will see other trees as well, so you won't know which trees are key trees. Ignore the fact that a target may be occluded. Our pre-algorithm takes care of that. 1) If this exists, what's it called? I can't find anything. 2) What do you think the odds are of having two identical location 'hits?' I imagine it's fairly rare. 3) If there are two identical location 'hits,' how can I determine my exact location after I move the robot next. (I assume the chances of having 2 occurrences of EXACT angles in a row, after I reposition the robot, would be statistically impossible, barring a forest growing in rows like corn). Would I just calculate the position again and hope for the best? Or would I somehow incorporate my previous position estimate into my next guess? If this exists, I'd like to read about it, and if not, develop it as a side project. I just don't have time to reinvent the wheel right now, nor have the time to implement this from scratch. So if it doesn't exist, I'll have to figure out another way to localize the robot since that's not the aim of this research, if it does, lets hope it's semi-easy.

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  • Interface Design Problem: Storing Result of Transactions

    - by jboyd
    Requirements: multiple sources of input (social media content) into a system multiple destinations of output (social media api's) sources and destinations WILL be added some pseudo: IContentProvider contentProvider = context.getBean("contentProvider"); List<Content> toPost = contentProvider.getContent(); for (Content c : toPost) { SocialMediaPresence smPresence = socialMediaService.getSMPresenceBySomeId(c.getDestId()); smPresence.hasTwitter(); smPresence.hasFacebook(); //just to show what this is smPresence.postContent(c); //post content could fail for some SM platforms, but shoulnd't be lost forever } So now I run out of steam, I need to know what content has been successfully posted, and if it hasn't gone too all platforms, or if another platform were added in the future that content needs to go out for it as well (therefore my content provider will need to not only know if content has gone out, but for what platforms). I'm not looking for code, although sample/pseudo is fine... I'm looking for an approach to this problem that I can implement

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  • How to make Spring accept fluent (non-void) setters?

    - by Chris
    Hi, I have an API which I am turning into an internal DSL. As such, most methods in my PoJos return a reference to this so that I can chain methods together declaratively as such (syntactic sugar). myComponent .setID("MyId") .setProperty("One") .setProperty2("Two") .setAssociation(anotherComponent) .execute(); My API does not depend on Spring but I wish to make it 'Spring-Friendly' by being PoJo friendly with zero argument constructors, getters and setters. The problem is that Spring seems to not detect my setter methods when I have a non-void return type. The return type of this is very convenient when chaining together my commands so I don't want to destroy my programmatic API just be to compatible with Spring injection. Is there a setting in Spring to allow me to use non-void setters? Chris

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  • Spring and hibernate.cfg.xml

    - by Steve Kuo
    How do I get Spring to load Hibernate's properties from hibernate.cfg.xml? We're using Spring and JPA (with Hibernate as the implementation). Spring's applicationContext.xml specifies the JPA dialect and Hibernate properties: <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean"> <property name="jpaDialect"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" /> </property> <property name="jpaProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.MySQLInnoDBDialect</prop> </props> </property> </bean> In this configuration, Spring is reading all the Hibernate properties via applicationContext.xml . When I create a hibernate.cfg.xml (located at the root of my classpath, the same level as META-INF), Hibernate doesn't read it at all (it's completely ignored). What I'm trying to do is configure Hibernate second level cache by inserting the cache properties in hibernate.cfg.xml: <cache usage="transactional|read-write|nonstrict-read-write|read-only" region="RegionName" include="all|non-lazy" />

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  • Memory leak - debugger and memory analyzer disagreeing

    - by Joe
    There is a memory leak in my android game - I've managed to narrow it down to a certain object, which has a list of objects to render on a texture. This object clears the list every time it draws though - so I can't work out how its managed to get thousands of elements in the list. I checked in the debugger and it doesn't have all these thousands of elements - usually about 2-20 which is what I'd expect... The game definitely slows down progressively only if I have rendering to texturing on. Here is a picture of Memory Analyzer showing 6,111 items: Memory Analyzer Here is a picture of the debugger showing 2: Debugger Can anyone help me find out whats wrong?

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  • Eclipse RCP setting classpath from workspace

    - by English Learner
    I am working one Eclipse RCP project where I have got one situation that I wanted to set classpath at runtime. So initially, I can set the classpath from project\lib\sample.jar file in order to avoid the compilation error. But once the Eclipse RCP application started, and click one update button, a new sample.jar file would be generated at workspace. Now I wanted to update the classpath for newly generated sample.jar from workspace. Which is the best option for setting such a runtime classpath ?

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  • Interrupt an Http Request blocked in read() on Android

    - by twk
    Using the Apache Http stack on Android, I'm trying to force a thread out of a call to read. This is what the stack looks like: OSNetworkSystem.receiveStreamImpl(FileDescriptor, byte[], int, int, int) line: not available [native method] OSNetworkSystem.receiveStream(FileDescriptor, byte[], int, int, int) line: 478 PlainSocketImpl.read(byte[], int, int) line: 565 SocketInputStream.read(byte[], int, int) line: 87 SocketInputBuffer(AbstractSessionInputBuffer).fillBuffer() line: 103 SocketInputBuffer(AbstractSessionInputBuffer).read(byte[], int, int) line: 134 IdentityInputStream.read(byte[], int, int) line: 86 EofSensorInputStream.read(byte[], int, int) line: 159 Fetcher.readStream() line: 89 I've tried InputStream.close(), Thread.Interrupt(), and HttpUriRequest.abort(), without any success. Any ideas? I'm also open to some kind of non-blocking IO, but I don't see any way to do that with the HttpUriRequest object. Thanks!

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  • UTF-8 and JTextArea

    - by ManWard
    hi i have 2 JTextArea that one of these contain Unicode Code point like this \u0645 i want another JTextArea show Character representation of this Unicode code point.but when pass this code point to JTextArea , it show code point not Character but if i set code point to JTextArea setText method directly it work correctly ! why ? and which can i pass String of Codepoint from one JTextArea to another ? thanks

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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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  • Using excel as UI without VB

    - by 01
    I think every business person would like to have excel UI, however they are forced into using web applications that sometimes look like really bad excel. Are there any frameworks that help build excel ui without VB? I dont mean framework like POI or JExcel that allows you to generate excel reports.

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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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  • Spring @Autowired and WebApplicationContext in Tomcat

    - by EugeneP
    @Autowired works only once. What to do to make it wire the bean every time the Servlet is recreated? My web-app (Tomcat6 container) consists of 2 Servlets. Every servlet has private fields. Their setters are marked with @Autowired In the init method I use WebApplicationContextUtils ... autowireBean(this); It autowires the properties marked with @Autowired once - during the initialization of the Servlet. Any other session will see these fields values, they will not be rewired after the previous session is destroyed. What to do to make them rewire them each time a Servlet constructor is called? a) Put the autowiring into the constructor? Or better 2) get a web app context and extract a bean from there?

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  • Google App Engine - Uploading blobs and authentication

    - by Keyur
    (I tried asking this on the GAE forums but didn't get an answer so am trying it here.) Currently to upload blobs, the app engine's blob store service creates a unique one- time URL that a user can post blobs to. My requirement is that I only want authenticated / authorized users to post blobs in my application. I can achieve this currently if the page that includes the multipart form to upload blobs is in my application. However, I am looking to providing a "REST API" for my users to upload their blobs. While it is true that the one-time nature of the upload URL mitigates the chances of rogue use but it's still possible. I was wondering if there is anyone on the app engine team here that can consider a feature where developers can register an upload listener. (Or if there is already a way, I'll be all ears). A standard servlet filter could also potentially do the job. This will give us an opportunity to authenticate / validate / decorate requests before the request gets forwarded to the blob store service. Thanks, Keyur

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  • How do Tomcat examples work?

    - by Bialecki
    Alright, this is a very simple question. I just installed Tomcat 6 on my Mac to play around with it, and every tutorial I look at says the first thing to do to create a new web application is to add a line to the server.xml file with defines a new Context. Fair enough. However, my question is, I don't see a line in there for the example web applications, so how do those work?

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  • Tomcat - Redirect to Error Page when ServletContextListener fails

    - by Vic
    When Tomcat starts it calls my ServletContextListener to obtain a database connection, which I will later use in other servlets with getServletContext(). It is called in my web.xml as: listener listener-class org.ppdc.database.DBCPoolingListener /listener-class /listener (I removed the < because they wouldn't display properly in this message. If I cannot connect to the database when Tomcat starts up I get a 404 error, because Tomcat cannot start the application. How can I redirect the user to a custom error page at this point? I tried the following in my web.xml (I have the < brackets in the original): (error-page) (error-code404/error-code) (location/file_not_found.html/location) (/error-page) Any ideas on how to redirect a user to one of my error pages when Tomcat tries to start the application? Thanks Vic

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  • Set HTML dropdown selected option using JSTL

    - by sarah
    In the same context i have another query ${productSubCategoryList} and the corresponding setting in request is like for(int i=0;i } here i have multiple select drop down ,even though i get the return value from for as two ,in the UI only one data is getting higlighted not the second one,What is wrong in the code ?

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  • Sorting a text file by date - Date looks like DD/MM/YYYY

    - by John N
    I am trying to sort the dates from the earliest to the latest. I was thinking about using the bufferedreader and do a try searching the first 2 characters of the string and then the 4th and 5th characters and finally the 7th and 8th characters, ignoring the slashes. The following is an example of the text file I have: 04/24/2010 - 2000.0 (Deposit) 09/05/2010 - 20.0 (Fees) 02/30/2007 - 600.0 (Deposit) 06/15/2009 - 200.0 (Fees) 08/23/2010 - 300.0 (Deposit) 06/05/2006 - 500.0 (Fees)

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  • HttpServletRequest.getServerName() occasionally returning null in concurrent use?

    - by oconnor0
    Under JBoss 4.0.1SP1, I have a servlet that makes multiple, concurrent calls to web services that are running under the same instance. I'm using request.getServerName() (on HttpServletRequest) to construct the endpoint URL. This normally works fine, but every once in a while returns null. I hadn't seen this before running the web service requests in parallel, and so I guessed that sharing the HttpServletRequest among threads won't always work or something. Any ideas on fixing this?

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  • Android: handle unexpected internet disconnect while downloading data

    - by M.A. Cape
    Hi, I have here a function that downloads data from a remote server to file. I am still not confident with my code. My question is, what if while reading the stream and saving the data to a file and suddenly I was disconnected in the internet, will these catch exceptions below can really catch that kind of incident? If not, can you suggest how to handle this kind of incident? Note: I call this function in a thread so that the UI won't be blocked. public static boolean getFromRemote(String link, String fileName, Context context){ boolean dataReceived = false; ConnectivityManager connec = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE); if (connec.getNetworkInfo(0).isConnected() || connec.getNetworkInfo(1).isConnected()){ try { HttpClient httpClient = new DefaultHttpClient(); HttpGet httpGet = new HttpGet(link); HttpParams params = httpClient.getParams(); HttpConnectionParams.setConnectionTimeout(params, 30000); HttpConnectionParams.setSoTimeout(params, 30000); HttpResponse response; response = httpClient.execute(httpGet); int statusCode = response.getStatusLine().getStatusCode(); if (statusCode == 200){ HttpEntity entity = response.getEntity(); InputStream in = null; OutputStream output = null; try{ in = entity.getContent(); String secondLevelCacheDir = context.getCacheDir() + fileName; File imageFile = new File(secondLevelCacheDir); output= new FileOutputStream(imageFile); IOUtilities.copy(in, output); output.flush(); } catch (IOException e) { Log.e("SAVING", "Could not load xml", e); } finally { IOUtilities.closeStream(in); IOUtilities.closeStream(output); dataReceived = true; } } }catch (SocketTimeoutException e){ //Handle not connecting to client !!!! Log.d("SocketTimeoutException Thrown", e.toString()); dataReceived = false; } catch (ClientProtocolException e) { //Handle not connecting to client !!!! Log.d("ClientProtocolException Thrown", e.toString()); dataReceived = false; }catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); dataReceived = false; Log.d("MalformedURLException Thrown", e.toString()); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); dataReceived = false; Log.d("IOException Thrown", e.toString()); } } return dataReceived; }

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