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  • Is nested synchronized block necessary?

    - by Dan
    I am writing a multithreaded program and I have a method that has a nested synchronized blocks and I was wondering if I need the inner sync or if just the outer sync is good enough. public class Tester { private BlockingQueue<Ticket> q = new LinkedBlockingQueue<>(); private ArrayList<Long> list = new ArrayList<>(); public void acceptTicket(Ticket p) { try { synchronized (q) { q.put(p); synchronized (list) { if (list.size() < 5) { list.add(p.getSize()); } else { list.remove(0); list.add(p.getSize()); } } } } catch (InterruptedException ex) { Logger.getLogger(Consumer.class.getName()).log(Level.SEVERE, null, ex); } } } EDIT: This isn't a complete class as I am still working on it. But essentially I am trying to emulate a ticket machine. The ticket machine maintains a list of tickets in the BlockingQueue q. Whenever a client adds a ticket to the machine, the machine also keeps track of the price of the last 5 tickets (ArrayList list)

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  • jpa @version optimistic locking

    - by cometta
    I loaded same entity record on 2 separate browser window then press submit (hibernate template.merge), version number incremented for both browser window, but never caught any problem with optimistic lock.. so how to test this? my save() look like this hibernatetemplate().merge(..); setJPAObject(null); //reset after save

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  • How can I tell NetBeans to use the latest available version of a JAR for a library?

    - by Freiheit
    I have a Netbeans project with a library defined which includes several JARs. These JARs are versioned like lib\blah\com.blah.wibble.jar_0.6.1.201004161543 . These are nightly builds from another project so that version changes often. I know I can point NetBeans at the specific JARs with the version name, but this means that every time I get a new version I have to update the NetBeans library. I can also strip the version name from the JARs, but this makes it hard to track down bugs. "What version of the blah JARs?" is usually the second thing we ask when we find a bug. Is it possible to tell Netbeans to use included com.blah.wibble.jar_[??????] where ???? is some sort of automatic pointer to use the latest available version?

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  • Parse Nested XML tags with the same name

    - by footose
    Let's take a simple XML document: <x> <e> <e> <e>Whatever 1</e> </e> </e> <e> <e> <e>Whatever 2</e> </e> </e> <e> <e> <e>Whatever 3</e> </e> </e> </x> Using the standard org.w3c.dom, I can get the nodes in X by doing.. NodeList fullnodelist = doc.getElementsByTagName("x"); But if I want to return the next set of "e" I try to use something like .. Element element = (Element) fullnodelist.item(0); NodeList nodes = pelement.getElementsByTagName("e"); Expecting it to return "3" nodes (because there are 3 sets of "e"), but instead, it returns "9" - becuase it gets all entries with "e" apperently. This would be fine in the above case, because I could probably iterate through and find what I'm looking for. The problem I'm having is that when the XML file looks like the following: <x> <e> <pattern>whatever</pattern> <blanks> <e>Something Else</e> </blanks> </e> <e> <pattern>whatever</pattern> <blanks> <e>Something Else</e> </blanks> </e> </x> When I request the "e" value, it returns 4, instead of (what i expect) 2. Am I just not understanding how the DOM parsing works? Typically in the past I have used my own XML documents so I would never name the items like this, but unfortunately this is not my XML file and I have no choice to work like this. What I thought I would do is write a loop that "drills down" nodes so that I could group each node together... public static NodeList getNodeList(Element pelement, String find) { String[] nodesfind = Utilities.Split(find, "/"); NodeList nodeList = null; for (int i = 0 ; i <= nodesfind.length - 1; i++ ) { nodeList = pelement.getElementsByTagName( nodesfind[i] ); pelement = (Element)nodeList.item(i); } // value of the nod we are looking for return nodeList; } .. So that if you passed "s/e" into the function, it would return the 2 nodes that I'm looking for (or elements, maybe I'm using the terminology incorrect?). instead it returns all of the "e" nodes within that node. I'm using J2SE for this, so options are rather limited. I can't use any third party XML Parsers. Anyway, if anyone is still with me and has a suggestion, it would be appreciated.

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  • 500 Worker Threads, what kind of thread pool?

    - by Submerged
    I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } The code that is executing is really simple and basically just this class aThread extends Thread { public void run(){ while(true){ Thread.sleep(ONE_MINUTE); //Lots of computation every minute } } } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful! Well, the design is arguably flawed. The threads implement Genetic-Programming or GP, a type of learning algorithm. Each thread analyzes advanced trends makes predictions. If the thread ever completes, the learning is lost. That said, I was hoping that sleep() would allow me to share some of the resources while one thread isn't "learning"

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  • Case Insensitive Ternary Search Tree

    - by Yan Cheng CHEOK
    I had been using Ternary Search Tree for a while, as the data structure to implement a auto complete drop down combo box. Which means, when user type "fo", the drop down combo box will display foo food football The problem is, my current used of Ternary Search Tree is case sensitive. My implementation is as follow. It had been used by real world for around 1++ yeas. Hence, I consider it as quite reliable. My Ternary Search Tree code However, I am looking for a case insensitive Ternary Search Tree, which means, when I type "fo", the drop down combo box will show me foO Food fooTBall Here are some key interface for TST, where I hope the new case insentive TST may have similar interface too. /** * Stores value in the TernarySearchTree. The value may be retrieved using key. * @param key A string that indexes the object to be stored. * @param value The object to be stored in the tree. */ public void put(String key, E value) { getOrCreateNode(key).data = value; } /** * Retrieve the object indexed by key. * @param key A String index. * @return Object The object retrieved from the TernarySearchTree. */ public E get(String key) { TSTNode<E> node = getNode(key); if(node==null) return null; return node.data; } An example of usage is as follow. TSTSearchEngine is using TernarySearchTree as the core backbone. Example usage of Ternary Search Tree // There is stock named microsoft and MICROChip inside stocks ArrayList. TSTSearchEngine<Stock> engine = TSTSearchEngine<Stock>(stocks); // I wish it would return microsoft and MICROCHIP. Currently, it just return microsoft. List<Stock> results = engine.searchAll("micro");

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  • Convert InputStream to String with encoding given in stream data

    - by Quentin
    Hi, My input is a InputStream which contains an XML document. Encoding used in XML is unknown and it is defined in the first line of XML document. From this InputStream, I want to have all document in a String. To do this, I use a BufferedInputStream to mark the beginning of the file and start reading first line. I read this first line to get encoding and then I use an InputStreamReader to generate a String with the correct encoding. It seems that it is not the best way to achieve this goal because it produces an OutOfMemory error. Any idea, how to do it ? public static String streamToString(final InputStream is) { String result = null; if (is != null) { BufferedInputStream bis = new BufferedInputStream(is); bis.mark(Integer.MAX_VALUE); final StringBuilder stringBuilder = new StringBuilder(); try { // stream reader that handle encoding final InputStreamReader readerForEncoding = new InputStreamReader(bis, "UTF-8"); final BufferedReader bufferedReaderForEncoding = new BufferedReader(readerForEncoding); String encoding = extractEncodingFromStream(bufferedReaderForEncoding); if (encoding == null) { encoding = DEFAULT_ENCODING; } // stream reader that handle encoding bis.reset(); final InputStreamReader readerForContent = new InputStreamReader(bis, encoding); final BufferedReader bufferedReaderForContent = new BufferedReader(readerForContent); String line = bufferedReaderForContent.readLine(); while (line != null) { stringBuilder.append(line); line = bufferedReaderForContent.readLine(); } bufferedReaderForContent.close(); bufferedReaderForEncoding.close(); } catch (IOException e) { // reset string builder stringBuilder.delete(0, stringBuilder.length()); } result = stringBuilder.toString(); }else { result = null; } return result; } Regards, Quentin

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  • How to get parent node in Stanford's JavaNLP?

    - by roddik
    Hello. Suppose I have such chunk of a sentence: (NP (NP (DT A) (JJ single) (NN page)) (PP (IN in) (NP (DT a) (NN wiki) (NN website)))) At a certain moment of time I have a reference to (JJ single) and I want to get the NP node binding A single page. If I get it right, that NP is the parent of the node, A and page are its siblings and it has no children (?). When I try to use the .parent() method of a tree, I always get null. The API says that's because the implementation doesn't know how to determine the parent node. Another method of interest is .ancestor(int height, Tree root), but I don't know how to get the root of the node. In both cases, since the parser knows how to indent and group trees, it must know the "parent" tree, right? How can I get it? Thanks

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  • Better to use constructor or method factory pattern?

    - by devoured elysium
    I have a wrapper class for the Bitmap .NET class called BitmapZone. Assuming we have a WIDTH x HEIGHT bitmap picture, this wrapper class should serve the purpose of allowing me to send to other methods/classes itself instead of the original bitmap. I can then better control what the user is or not allowed to do with the picture (and I don't have to copy the bitmap lots of times to send for each method/class). My question is: knowing that all BitmapZone's are created from a Bitmap, what do you find preferrable? Constructor syntax: something like BitmapZone bitmapZone = new BitmapZone(originalBitmap, x, y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.From(originalBitmap, x , y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.FromBitmap(originalBitmap, x, y, width, height); Other? Why? Thanks

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  • taglib with constants functionality?

    - by jack
    I need to use some constants in my JSP. Now I'd like to use this without using scriptlets. (and adding getters is not an option, it's an external jar) Using the search I've seen that some people put them in a map. However I've seen that there's a constants function in the unstandard taglib but that is a few years old and so far I haven't found a maven repository with it. So are there any other taglibs with this functionality?

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  • How to differentiate between Programmer and JVM Exceptions

    - by Haxed
    As the title suggests, how can I tell a JVM thrown exception from a Programmatically(does this mean, thrown by a programmer or the program) thrown exception ? JVM Exceptions 1) ArrayIndexOutOfBoundsException 2) ClassCastException 3) NullPointerException Programmatically thrown 1) NumberFormatException 2) AssertionError Many Thanks

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  • Pageview implementation

    - by The Elite Gentleman
    Hi everyone I want to add a pageview feature on my current web application. This page view is based on the count of user viewing the page. It must be unique, i.e. I must not view a person's page 10000 times and record it as 10000 views, just record 1 view instead. My question is, should I base my pageview count on IP address? If not, what is/are the best approach in doing this? I know that if the person has logged in to my system, I can simply use the user id stored in the session and check on the record if the user has/hasn't viewed the page and update accordingly. But for "anonymous" viewers, what is the best approach? Thanks. PS How does Youtube does it?

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  • Spring hibernate ehcache setup

    - by Johan Sjöberg
    I have some problems getting the hibernate second level cache to work for caching domain objects. According to the ehcache documentation it shouldn't be too complicated to add caching to my existing working application. I have the following setup (only relevant snippets are outlined): @Entity @Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE public void Entity { // ... } ehcache-entity.xml <cache name="com.company.Entity" eternal="false" maxElementsInMemory="10000" overflowToDisk="true" diskPersistent="false" timeToIdleSeconds="0" timeToLiveSeconds="300" memoryStoreEvictionPolicy="LRU" /> ApplicationContext.xml <bean class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"> <property name="dataSource" ref="ds" /> <property name="annotatedClasses"> <list> <value>com.company.Entity</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.generate_statistics">true</prop> <prop key="hibernate.cache.use_second_level_cache">true</prop> <prop key="net.sf.ehcache.configurationResourceName">/ehcache-entity.xml</prop> <prop key="hibernate.cache.region.factory_class">net.sf.ehcache.hibernate.SingletonEhCacheRegionFactory</prop> .... </property> </bean> Maven dependencies <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-annotations</artifactId> <version>3.4.0.GA</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-hibernate3</artifactId> <version>2.0.8</version> <exclusions> <exclusion> <artifactId>hibernate</artifactId> <groupId>org.hibernate</groupId> </exclusion> </exclusions> </dependency> <dependency> <groupId>net.sf.ehcache</groupId> <artifactId>ehcache-core</artifactId> <version>2.3.2</version> </dependency> A test class is used which enables cache statistics: Cache cache = cacheManager.getCache("com.company.Entity"); cache.setStatisticsAccuracy(Statistics.STATISTICS_ACCURACY_GUARANTEED); cache.setStatisticsEnabled(true); // store, read etc ... cache.getStatistics().getMemoryStoreObjectCount(); // returns 0 No operation seems to trigger any cache changes. What am I missing? Currently I'm using HibernateTemplate in the DAO, perhaps that has some impact. [EDIT] The only ehcache log output when set to DEBUG is: SettingsFactory: Cache region factory : net.sf.ehcache.hibernate.SingletonEhCacheRegionFactory

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  • Lucene document Boosting

    - by athreyar
    Hello, I am having problem with lucene boosting, Iam trying to boost a particular document which matches with the (firstname)field specified I have posted the part of the codeenter code hereprivate static Document createDoc(String lucDescription,String primaryk,String specialString){ Document doc = new Document(); doc.add(new Field("lucDescription",lucDescription, Field.Store.NO, Field.Index.TOKENIZED)); doc.add(new Field("primarykey",primaryk,Field.Store.YES,Field.Index.NO)); doc.add(new Field("specialDescription",specialString, Field.Store.NO, Field.Index.UN_TOKENIZED)); doc.setBoost ((float)(0.00001)); if (specialString.equals("chris")) doc.setBoost ((float)(100000.1)); return doc; } why is this not working?enter code herepublic static String dbSearch(String searchString){ List pkList = new ArrayList(); String conCat="("; try{ String querystr = searchString; Query query = new QueryParser("lucDescription", new StandardAnalyzer()).parse(querystr); IndexSearcher searchIndex = new IndexSearcher("/home/athreya/docsIndexFile"); // Index of the User table-- /home/araghu/aditya/indexFile. Hits hits = searchIndex.search(query); System.out.println("Found " + hits.length() + " hits."); for(int iterator=0;iterator Thank you in advance Athreya

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  • HttpPost request unsuccessful

    - by The Thom
    I have written a web service and am now writing a tester to perform integration testing from the outside. I am writing my tester using apache httpclient 4.3. Based on the code here: http://hc.apache.org/httpcomponents-client-4.3.x/quickstart.html and here: http://hc.apache.org/httpcomponents-client-4.3.x/tutorial/html/fundamentals.html#d5e186 I have written the following code. Map<String, String> parms = new HashMap<>(); parms.put(AirController.KEY_VALUE, json); postUrl(SERVLET, parms); ... protected String postUrl(String servletName, Map<String, String> parms) throws AirException{ String url = rootUrl + servletName; HttpPost post = new HttpPost(url); List<NameValuePair> nvps = new ArrayList<NameValuePair>(); for(Map.Entry<String, String> entry:parms.entrySet()){ BasicNameValuePair parm = new BasicNameValuePair(entry.getKey(), entry.getValue()); nvps.add(parm); } try { post.setEntity(new UrlEncodedFormEntity(nvps)); } catch (UnsupportedEncodingException use) { String msg = "Invalid parameters:" + parms; throw new AirException(msg, use); } CloseableHttpResponse response; try { response = httpclient.execute(post); } catch (IOException ioe) { throw new AirException(ioe); } String result; if(HttpStatus.SC_OK == response.getStatusLine().getStatusCode()){ result = processResponse(response); } else{ String msg = MessageFormat.format("Invalid status code {0} received from query {1}.", new Object[]{response.getStatusLine().getStatusCode(), url}); throw new AirException(msg); } return result; } This code successfully reaches my servlet. In my servlet, I have (using Spring's AbstractController): protected ModelAndView post(HttpServletRequest request, HttpServletResponse response) { String json = String.valueOf(request.getParameter(KEY_VALUE)); if(json.equals("null")){ log.info("Received null value."); response.setStatus(406); return null; } And this code always falls into the null parameter code and returns a 406. I'm sure I'm missing something simple, but can't see what it is.

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  • Eclipse Class File Metadata

    - by Alex
    In Visual Studio, I can obtain a succinct list of public methods/members exposed in a class for which I do not have the source (i.e. bundled inside a DLL) by pressing F12 (GoToDefinition). Similarly, I am learning the Android API - in Eclipse. Jumping to an Android framework method definition produces decompilation output which is not intuitive to read, and is very verbose. To mimic results like Visual Studio, I am considering several options: How can I format the decompilation output to be 'cleaner' - I have looked through Eclipse's preferences menus and have not found a way to do this. How do I 'add corresponding source files' once Google provides it, so that jumping to definition yields the actual definition? Is there a plugin that does this already? I looked into Jadclipse, but that project has not been updated in several years, and is still a decompiler. Thank you in advance.

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  • Spring Transactional Parameterized Test and Autowiring

    - by James Kingsbery
    Is there a way to get a class that extends AbstractTransactionalJUnit4SpringContexts to play nicely with JUnit's own @RunWith(Parameterized), so that fields marked as Autowired get wired in properly? @RunWith(Parameterized) public class Foo extends AbstractTransactionalJUnit4SpringContexts { @Autowired private Bar bar @Parameters public static Collection data() { // return parameters, following pattern in // http://junit.org/apidocs/org/junit/runners/Parameterized.html } @Test public void someTest(){ bar.baz() //NullPointerException } }

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  • JDO, GAE: Load object group by child's key

    - by tiex
    I have owned one-to-many relationship between two objects: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class AccessInfo { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private com.google.appengine.api.datastore.Key keyInternal; ... @Persistent private PollInfo currentState; public AccessInfo(){} public AccessInfo(String key, String voter, PollInfo currentState) { this.voter = voter; this.currentState = currentState; setKey(key); // this key is unique in whole systme } public void setKey(String key) { this.keyInternal = KeyFactory.createKey( AccessInfo.class.getSimpleName(), key); } public String getKey() { return this.keyInternal.getName(); } and @PersistenceCapable(identityType = IdentityType.APPLICATION) public class PollInfo { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; @Persistent(mappedBy = "currentState") private List<AccessInfo> accesses; ... I created an instance of class PollInfo and make it persistence. It is ok. But then I want to load this group by AccessInfo key, and I am getting exception NucleusObjectNotFoundException. Is it possible to load a group by child's key?

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  • How can i edit OSGi bundles manifest file in Netbeans 6.9?

    - by Deniz Acay
    I'm using Netbeans 6.9 RC2 and Maven OSGi Bundle project template. Actually i dont want to test my bundles in Netbeans environment so i copy the jar file to the OSGi container directory and install it from command line. But when i want to see its headers from OSGi console, i see a lot of Netbeans related unnecessary stuff. Is it possible to edit the contents of the manifest file in Netbeans?

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  • Can Hibernate default a Null String to Empty String

    - by sliver
    In our application we are pulling data from a DB2 mainframe database. If the database has "low values" in a field, hibernate sends a "null" value in the object. This occurs even if the column is defined as "not null". As we are doing XML parsing on this, Castor is having trouble with it. I would like to fix this in Hibernate. Also, all of the hibernate hbm files are generated, so we can't mess with them (they are regened from time to time.) Any way to intercept all Strings and replace nulls with ""?

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