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  • understanding list[i-1] vs list[i]-1

    - by user3720527
    Hopefully this is a simple answer that I am just failing to understand. Full code is public static void mystery(int[] list) { for( int i = list.length - 1; i>1; i --) { if (list[i] > list[i - 1]) { list[i -1] = list[i] - 2; list[i]++; } } } } and lets say we are using a list of [2,3,4]. I know that it will output 2,2,5 but I am unclear how to actually work through it. I understand that the list.length is 3 here, and I understand that the for loop will only run once, but I am very unclear what happens at the list[i - 1] = list[i] - 2; area. Should it be list[2-1] = list[2] - 2? How does the two being outside the bracket effect it differently? Much thanks.

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  • Weak hashmap with weak references to the values?

    - by Razor Storm
    I am building an android app where each entity has a bitmap that represents its sprite. However, each entity can be be duplicated (there might be 3 copies of entity asdf for example). One approach is to load all the sprites upfront, and then put the correct sprite in the constructors of the entities. However, I want to decode the bitmaps lazily, so that the constructors of the entities will decode the bitmaps. The only problem with this is that duplicated entities will load the same bitmap twice, using 2x the memory (Or n times if the entity is created n times). To fix this, I built a SingularBitmapFactory that will store a decoded Bitmap into a hash, and if the same bitmap is asked for again, will simply return the previously hashed one instead of building a new one. Problem with this, though, is that the factory holds a copy of all bitmaps, and so won't ever get garbage collected. What's the best way to switch the hashmap to one with weakly referenced values? In otherwords, I want a structure where the values won't be GC'd if any other object holds a reference to it, but as long as no other objects refers it, then it can be GC'd.

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  • Thread testing for time

    - by DanielFH
    Hi there :) I'm making a thread for my application that's going to do an exit operation at a given time (only hours and minutes, day/month doesn't matter). Is this the right way to do it, and also the right way to test for time? I'm testing for a 24 hour clock by the way, not AM / PM. I'm then in another class going to call this something like new Thread(new ExitThread()).start(); public class ExitThread implements Runnable { @Override public void run() { Date date = new Date(System.currentTimeMillis()); String time = new SimpleDateFormat("HHmmss").format(date); int currentTime = Integer.parseInt(time); int exitTime = 233000; while(true) { try { Thread.sleep(10000); } catch (InterruptedException e) { e.printStackTrace(); } if(currentTime >= exitTime ) { // do exit operation here } } } Thanks. //D

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  • non-servlet JSP

    - by h2g2java
    I realise there are EL and near EL frameworks like StringTemplate, JUEL, Velocity, etc. However, I am not asking for list of alternatives to JSTL/EL. I came across a package more than a year ago, someone who wrote a util that emulates the functionality of JSP for non-servlet env, i.e., JSP composition which does not need a "servlet container" to function. I ignored it and now I think it would be helpful to me and I need help to recall what it is. My actual motivation is similar to what StringTemplate, JUEL, Velocity would offer to help me compose SQL blocks, HTML blocks but I am thinking that JSPs are precompiled into bytecode and JSPs are more run-time efficient since run-time parsing is done no more than once. So actually, recommendation for alternatives would be acceptable as long as the templates are precompiled into bytecode. But I still prefer the JSP emulator.

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  • translating specifications into query predicates

    - by Jeroen
    I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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  • twitter basic authorisation not working?

    - by Bunny Rabbit
    URL url = new URL("http://twitter.com/statuses/update.xml"); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setDoOutput(true); String cridentials = new sun.misc.BASE64Encoder().encode((username + ":" + password).getBytes()); conn.setRequestProperty ("Authorization", "Basic " + cridentials); OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream()); wr.write(status); wr.flush(); wr.close(); why the above code for updating twitter status is not working ? i am running it on google app engine.

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  • How a servlet can get the absolute path to a file outside of the servlet?

    - by WolfmanDragon
    We have been using System.getProperties("user.dir") to get the location of a properties file. Now that it has been deployed on Tomcat(via servlet), the System call is giving the location as tomcat and not at the location at where the properties file exist. How can we call the the properties file dynamically? Given: Tomcat is not the only way the app will be deployed We have no control on where the app may be placed. Relative paths will not work as that Vista is being used and Vista breaks relative paths. This must work on all OS, including(but not limited to) Linux, XP and Vista. EDIT I implied this, but in case I was not clear enough, I have no way of knowing the path String.

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  • Android Content Provider database leak issue

    - by MattC
    I am writing a content provider for this application and in my content provider I am opening a database connection, running a query and returning the cursor of results to the calling program. If I close this database connection in the provider, the cursor has no results. If I leave it open, I get "leak found" errors in my DDMS log. What am I missing here? What's the clean, proper way to return a cursor of database results?

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  • I would like to useJava 7's FileVisitor to walk up a tree

    - by John Ormerod
    I have looked and searched for some guidance on how to start at a low point in a path and walk up (or 'back'), until I find a folder with the name I am searching for. The FileVisitor class looks like it ought to be able to help me, but it only seems to work from head to toe. Is there something that someone could point me to? Thanks, John {edited: I seem to be discouraged from saying thanks to the two people who replied in a comment. So thanks! I had a 'duh!' moment when I saw the simple approach. And the article looks useful to someone starting to use FileVisitor. Put them together, and I could go up and then down, if I needed to. John]

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  • Hibernate Query for a List of Objects that matches a List of Objects' ids

    - by sal
    Given a classes Foo, Bar which have hibernate mappings to tables Foo, A, B and C public class Foo { Integer aid; Integer bid; Integer cid; ...; } public class Bar { A a; B b; C c; ...; } I build a List fooList of an arbitrary size and I would like to use hibernate to fetch List where the resulting list will look something like this: Bar[1] = [X1,Y2,ZA,...] Bar[2] = [X1,Y2,ZB,...] Bar[3] = [X1,Y2,ZC,...] Bar[4] = [X1,Y3,ZD,...] Bar[5] = [X2,Y4,ZE,...] Bar[6] = [X2,Y4,ZF,...] Bar[7] = [X2,Y5,ZG,...] Bar[8] = ... Where each Xi, Yi and Zi represents a unique object. I know I can iterate fooList and fetch each List and call barList.addAll(...) to build the result list with something like this: List<bar> barList.addAll(s.createQuery("from Bar bar where bar.aid = :aid and ... ") .setEntity("aid", foo.getAid()) .setEntity("bid", foo.getBid()) .setEntity("cid", foo.getCid()) .list(); ); Is there any easier way, ideally one that makes better use of hibernate and make a minimal number of database calls? Am I missing something? Is hibernate not the right tool for this?

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  • Are there any guarantees in JLS about order of execution static initialization blocks?

    - by Roman
    I wonder if it's reliable to use a construction like: private static final Map<String, String> engMessages; private static final Map<String, String> rusMessages; static { engMessages = new HashMap<String, String> () {{ put ("msgname", "value"); }}; rusMessages = new HashMap<String, String> () {{ put ("msgname", "????????"); }}; } private static Map<String, String> msgSource; static { msgSource = engMessages; } public static String msg (String msgName) { return msgSource.get (msgName); } Is there a possibility that I'll get NullPointerException because msgSource initialization block will be executed before the block which initializes engMessages? (about why don't I do msgSource initialization at the end of upper init. block: just the matter of taste; I'll do so if the described construction is unreliable)

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  • JAXB Customizations and List<Object>

    - by DaUltimateTrooper
    Hi everybody. I used JAXB to create some classes from an XSD. The result was not quite what I expected and most probably it can be customized. It created a generic list instead of 3 different lists. Can this be corrected somehow? @XmlElements({ @XmlElement(name = "M1", type = M1_Type.class), @XmlElement(name = "M2", type = M2_Type.class), @XmlElement(name = "M3", type = M3_Type.class) }) protected List<Object> m1Orm2OrM3; Is there a customization to fix this?

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  • Google App Engine - DELETE JPQL Query and Cascading

    - by Taylor Leese
    I noticed that the children of PersistentUser are not deleted when using the JPQL query below. However, the children are deleted if I perform an entityManager.remove(object). Is this expected? Why doesn't the JPQL query below also perform a cascaded delete? @OneToMany(mappedBy = "persistentUser", cascade = CascadeType.ALL) private Collection<PersistentLogin> persistentLogins; ... @Override @Transactional public final void removeUserTokens(final String username) { final Query query = entityManager.createQuery( "DELETE FROM PersistentUser p WHERE username = :username"); query.setParameter("username", username); query.executeUpdate(); }

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  • Migrating from hand-written persistence layer to ORM

    - by Sergey Mikhanov
    Hi community, We are currently evaluating options for migrating from hand-written persistence layer to ORM. We have a bunch of legacy persistent objects (~200), that implement simple interface like this: interface JDBC { public long getId(); public void setId(long id); public void retrieve(); public void setDataSource(DataSource ds); } When retrieve() is called, object populates itself by issuing handwritten SQL queries to the connection provided using the ID it received in the setter (this usually is the only parameter to the query). It manages its statements, result sets, etc itself. Some of the objects have special flavors of retrive() method, like retrieveByName(), in this case a different SQL is issued. Queries could be quite complex, we often join several tables to populate the sets representing relations to other objects, sometimes join queries are issued on-demand in the specific getter (lazy loading). So basically, we have implemented most of the ORM's functionality manually. The reason for that was performance. We have very strong requirements for speed, and back in 2005 (when this code was written) performance tests has shown that none of mainstream ORMs were that fast as hand-written SQL. The problems we are facing now that make us think of ORM are: Most of the paths in this code are well-tested and are stable. However, some rarely-used code is prone to result set and connection leaks that are very hard to detect We are currently squeezing some additional performance by adding caching to our persistence layer and it's a huge pain to maintain the cached objects manually in this setup Support of this code when DB schema changes is a big problem. I am looking for an advice on what could be the best alternative for us. As far as I know, ORMs has advanced in last 5 years, so it might be that now there's one that offers an acceptable performance. As I see this issue, we need to address those points: Find some way to reuse at least some of the written SQL to express mappings Have the possibility to issue native SQL queries without the necessity to manually decompose their results (i.e. avoid manual rs.getInt(42) as they are very sensitive to schema changes) Add a non-intrusive caching layer Keep the performance figures. Is there any ORM framework you could recommend with regards to that?

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  • Configure autocomplete in intellij with hamcrest and mockito dsl

    - by sgargan
    I'm wondering if its possible to configure Intellij's smart insert to suggest hamcrest and mockito dsl idioms when in test classes. Really I'm looking for something like eclipse's 'static favorites', so that when I hit ctrl + space or ctrl +shift +space the idioms are present. In general is it possible to configure autocomplete/smart insert or the suggestions balloon for that matter. I've looked through the settings without much luck but could easily have overlooked something.

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  • how many times a word appears into a txt file

    - by m4g4bu
    I've a problem when i tried to count how many time a word appears into a txt file. 1/ I create a textfield ( txta ) 2/ I create a button to apply the action ( btn ) 3/ I create a textarea ( area ) that is the place where the content of the file is displayed When I select the file, the content of the file is displayed on area, then I enter the word in txta to search and then I clicked the btn but the code is not working public int contarPalabras(String chain, String word) { // Recibe un string y una palabra y devuelve la cantidad de veces que encontró esa palabra en el string. // Si no encuentra la letra devuelve (-1). int cant = 0; int intIndex = chain.indexOf(word); if(intIndex == - 1){ cant = -1; }else{ cant = intIndex; } return cant; }

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  • Why is my keyboard messed up in Eclipse?

    - by Xi
    Hi there: I am trying to type in a pair of angle brackets in Eclipse, like "<". However it shows up as a single quotation and a dot, like "'.". I tried a couple of times and found out that the angle bracket is actually located at back-slash's position. Why is this happening? How can I change it back? Thanks in advance. Xi

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  • j2me PushRegistry.RegisterAlarm and code signing

    - by Mihir
    I am developing an app on Nokia C2-00 in which I am using push registry for auto start of app on some fixed time ex. PushRegistry.registerAlarm("ClassName", alarm.getTime()); this is working perfect and it starts app on that time. But this is asking me for permissions two times. 1) when I am registering alarm using PushRegistry.registerAlarm("ClassName", alarm.getTime()); 2) when app start on that defined time. in this and this link I found that if my application is signed then it will not ask for permission when app autostart. but I am not sure about the time when my code will register alarm. Will it ask for permission or not?

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  • readUTF timeout

    - by Hassan Voyeau
    I am getting a timeout with the following code at readUTF. Any idea why? hc = (HttpConnection) Connector.open("http://twitter.com/statuses/user_timeline/" + username + ".json"); int rc = hc.getResponseCode(); if (rc != HttpConnection.HTTP_OK) { throw new IOException("HTTP response code: " + rc); } DataInputStream dataInputStream = hc.openDataInputStream(); String list = dataInputStream.readUTF();

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  • One liner for getting a sublist from a Set

    - by yegor256
    Is there a one-liner (maybe from Guava or Apache Collections) that gets a sublist from a set. Internally it should do something like this: public <T> List<T> sublist(Set<T> set, int count) { Iterator<T> iterator = set.iterator(); List<T> sublist = new LinkedList<T>(); int pos = 0; while (iterator.hasNext() && pos++ < count) { sublist.add(iterator.next()); } return sublist; } Obviously, if there are not enough elements it has to return as many as possible.

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