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  • Getting a nicely formatted timestamp without lots of overhead?

    - by Brad Hein
    In my app I have a textView which contains real-time messages from my app, as things happen, messages get printed to this text box. Each message is time-stamped with HH:MM:SS. Up to now, I had also been chasing what seemed to be a memory leak, but as it turns out, it's just my time-stamp formatting method (see below), It apparently produces thousands of objects that later get gc'd. For 1-10 messages per second, I was seeing 500k-2MB of garbage collected every second by the GC while this method was in place. After removing it, no more garbage problem (its back to a nice interval of about 30 seconds, and only a few k of junk typically) So I'm looking for a new, more lightweight method for producing a HH:MM:SS timestamp string :) Old code: /** * Returns a string containing the current time stamp. * @return - a string. */ public static String currentTimeStamp() { String ret = ""; Date d = new Date(); SimpleDateFormat timeStampFormatter = new SimpleDateFormat("hh:mm:ss"); ret = timeStampFormatter.format(d); return ret; }

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  • Fastest way to put contents of Set<String> to a single String with words separated by a whitespace?

    - by Lars Andren
    I have a few Set<String>s and want to transform each of these into a single String where each element of the original Set is separated by a whitespace " ". A naive first approach is doing it like this Set<String> set_1; Set<String> set_2; StringBuilder builder = new StringBuilder(); for (String str : set_1) { builder.append(str).append(" "); } this.string_1 = builder.toString(); builder = new StringBuilder(); for (String str : set_2) { builder.append(str).append(" "); } this.string_2 = builder.toString(); Can anyone think of a faster, prettier or more efficient way to do this?

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  • Returning the element number of the longest string in an array

    - by JohnRoberts
    I'm trying to get the longestS method to take the user-inputted array of strings, then return the element number of the longest string in that array. I got it to the point where I was able to return the number of chars in the longest string, but I don't believe that will work for what I need. My problem is that I keep getting incompatible type errors when trying to figure this out. I don't understand the whole data type thing with strings yet. It's confusing me how I go about return a number of the array yet the array is of strings. The main method is fine, I got stuck on the ???? part. { public static void main(String [] args) { Scanner inp = new Scanner( System.in ); String [] responseArr= new String[4]; for (int i=0; i<4; i++) { System.out.println("Enter string "+(i+1)); responseArr[i] = inp.nextLine(); } int highest=longestS(responseArr); } public static int longestS(String[] values) { int largest=0 for( int i = 1; i < values.length; i++ ) { if ( ????? ) } return largest; } }

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  • How can i use Stopwatch [ apache ] to calculate the time taken by a method?

    - by Rakesh Juyal
    I am using StopWatch [ apache ] to get the time taken by my method. The approach i am following is StopWatch stopWatch = new StopWatch(); stopWatch.start(); myMethod(); stopWatch.stop(); logger.info( "Time taken by myMethod: " + stopWatch.getTime() + " millisecs"); stopWatch.reset(); stopWatch.start(); anotherMethod(); stopWatch.stop(); logger.info( "Time taken by anotherMethod: " + stopWatch.getTime() + " millisecs"); Thats the only thing i know about StopWatch :). How/when to use split(), unsplit(), getSplitTime(),suspend()... ?

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  • Updating position of JSlider Swing

    - by GLRockwell
    My apologies for posting tons of questions as of late. I'm trying to get a JSlider to update its position based on a constantly updating variable. The setValue(n) method doesn't seem to work. Is there any alternative? We're using this as a time marker for a music player.

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  • Webapp: safetly update a shared List/Map in the AppContext

    - by al nik
    I've Lists and Maps in my WebAppContext. Most of the time these are only read by multiple Threads but sometimes there's the need to update or add some data. I'm wondering what's the best way to do this without incurring in a ConcurrentModificationException. I think that using CopyOnWriteArrayList I can achieve what I want in terms of - I do not have to sync on every read operation- I can safety update the list while other threads are reading it. Is this the best solution? What about Maps?

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  • MySQL best usage in Tomcat?

    - by mabuzer
    Which one is better way of using MySQL in Tomcat : A) assign a DB connection for user as long as it's session is valid. [OR] B) open connection to DB, on every request come to server and when it's done close that. ?

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  • Jetty RewriteHandler and RewriteRegexRule

    - by Justin
    I'm trying to rewrite a URL for a servlet. The URL gets rewritten correctly, but the context doesn't match after that. Any idea how to get this to work? RewriteHandler rewriteHandler = new RewriteHandler(); rewriteHandler.setRewriteRequestURI(true); rewriteHandler.setRewritePathInfo(true); rewriteHandler.setOriginalPathAttribute("requestedPath"); RewriteRegexRule rewriteRegexRule = new RewriteRegexRule(); rewriteRegexRule.setRegex("/r/([^/]*).*"); rewriteRegexRule.setReplacement("/r?z=$1"); rewriteHandler.addRule(rewriteRegexRule); ContextHandlerCollection contextHandlerCollection = new ContextHandlerCollection(); Context servletContext = new Context(contextHandlerCollection, "/"); servletContext.addServlet(new ServletHolder(new RedirectServlet()), "/r"); So basically /r/asdf gets rewritten to /r?z=asdf. However, the rewritten /r?z=asdf is now not processed by the servlet. Also, /r?z=asdf does work if called directly.

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  • Commercial Website architecture question

    - by Maxime ARNSTAMM
    Hello everyone, I have to write an architecture case study but there are some things that i don't know, so i'd like some pointers on the following : The website must handle 5k simultaneous users. The backend is composed by a commercial software, some webservices, some message queues, and a database. I want to recommend to use Spring for the backend, to deal with the different elements, and to expose some Rest services. I also want to recommend wicket for the front (not the point here). What i don't know is : must i install the front and the back on the same tomcat server or two different ? and i am tempted to put two servers for the front, with a load balancer (no need for session replication in this case). But if i have two front servers, must i have two back servers ? i don't want to create some kind of bottleneck. Based on what i read on this blog a really huge charge is handle by one tomcat only for the first website mentionned. But i cannot find any info on this, so i can't tell if it seems plausible. If you can enlight me, so i can go on in my case study, that would be really helpful. Thanks :)

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  • Spring-Security http-basic auth in addition to other authentication types

    - by Keith
    I have a pretty standard existing webapp using spring security that requires a database-backed form login for user-specific paths (such as /user/**), and some completely open and public paths (such as /index.html). However, as this webapp is still under development, I'd like to add a http-basic popup across all paths (/**) to add some privacy. Therefore, I'm trying to add a http-basic popup that asks for a universal user/pass combo (ex admin/foo) that would be required to view any path, but then still keep intact all of the other underlying authentication mechanisms. I can't really do anything with the <http> tag, since that will confuse the "keep out the nosy crawlers" authentication with the "user login" authentication, and I'm not seeing any way to associate different paths with different authentication mechanisms. Is there some way to do this with spring security? Alternatively, is there some kind of a dead simple filter that I can apply independently of spring-security's authentication mechanisms?

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  • Customizing error handling of JAXB unmarshall process

    - by ekeren
    Assuming I have a schema that describes a root element class Root that contains a List<Entry> where the Entry class has a required field name. Here is how it looks in code: @XmlRootElement class Root{ @XmlElement(name="entry") public List<Entry> entries = Lists.newArrayList(); } @XmlRootElement class Entry{ @XmlElement(name="name",required=true) public String name; } If I supply the following XML for unmarshalling: <root> <entry> <name>ekeren</name> </entry> <entry> </entry> </root> I have a problem because the second entry does not contain a name. So unmarshall produces null. Is there a way to customize JAXB to unmarshall a Root object that will only contain the "good" entry?

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  • How to click through JGlassPane With MouseListener to UI behind it

    - by Epicmaster
    I have a JFrame and a bunch of JComponents on top of the JFrame. I need to make use of the JGlassPane and I used this implementation to set it up. JPanel glass = new JPanel(); frame.setGlassPane(glass); glass.setVisible(true); glass.setOpaque(false); After doing so I can't select any JButtons or other JComponents under the JGlassPane. Is there a way to have only the components on the GlassPane selectable while still having the ability to select components under the GlassPane? Edit I forgot to mention (not knowing this would be relevant) that I did attach both a MouseListener and a MouseMotionListener to the glass pane. Is there a way to pass the Mouse Events to other components and only use them when needed?

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  • Recommendations for an in memory database vs thread safe data structures

    - by yx
    TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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  • Hibernate many-to-many mapping not saved in pivot table

    - by vincent
    I having problems saving many to many relationships to a pivot table. The way the pojos are created is unfortunately a pretty long process which spans over a couple of different threads which work on the (to this point un-saved) object until it is finally persisted. I associate the related objects to one another right after they are created and when debugging I can see the List of related object populated with their respective objects. So basically all is fine to this point. When I persist the object everything get saved except the relations in the pivot table. mapping files: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.thebeansgroup.jwinston.plugin.orm.hibernate.object"> <class name="ShowObject" table="show_object"> <id name="id"> <generator class="native" /> </id> <property name="name" /> <set cascade="all" inverse="true" name="venues" table="venue_show"> <key column="show_id"/> <many-to-many class="VenueObject"/> </set> </class> </hibernate-mapping> and the other <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.thebeansgroup.jwinston.plugin.orm.hibernate.object"> <class name="VenueObject" table="venue_object"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <property name="latitude" type="integer"/> <property name="longitude" type="integer"/> <set cascade="all" inverse="true" name="shows" table="venue_show"> <key column="venue_id"/> <many-to-many class="ShowObject"/> </set> </class> </hibernate-mapping> pojos: public class ShowObject extends OrmObject { private Long id; private String name; private Set venues; public ShowObject() { } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set getVenues() { return venues; } public void setVenues(Set venues) { this.venues = venues; } } and the other: public class VenueObject extends OrmObject { private Long id; private String name; private int latitude; private int longitude; private Set shows = new HashSet(); public VenueObject() { } @Id @GeneratedValue(strategy = GenerationType.AUTO) public Long getId() { return id; } public void setId(Long id) { this.id = id; } public int getLatitude() { return latitude; } public void setLatitude(int latitude) { this.latitude = latitude; } public int getLongitude() { return longitude; } public void setLongitude(int longitude) { this.longitude = longitude; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set getShows() { return shows; } public void setShows(Set shows) { this.shows = shows; } } Might the problem be related to the lack of annotations?

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  • How to refresh an activity? Map View refresh fails

    - by poeschlorn
    Hi Guys, after implementing some Android Apps, including several Map activities, I try to refresh the activity when the GPS listener's onLocationChanged() mehtod is called. I have no idea how to tell the map activity to refresh on its own and display the new coords... the coords to store will have to be in global values, so that the location listener will have access to it. In my sample GPS-class (see code below) I just changed the text of a text view....but how to do that in map view? private class MyLocationListener implements LocationListener { @Override public void onLocationChanged(Location loc) { final TextView tv = (TextView) findViewById(R.id.myTextView); if (loc != null) { tv.setText("Location changed : Lat: " + loc.getLatitude() + " Lng: " + loc.getLongitude()); } } I think the solution of this Problem won't be very difficult, but I just need the beginning ;-) This whole app shall work like a really simple navigation system. It would be great if someone could help me a little bit further :) nice greetings, Poeschlorn

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  • Using a Session Scoped Bean

    - by jboyd
    The following code is returning null: private MyAppUser getMyAppUser(HttpSession session) { MyAppUser myAppUser = (MyAppUser) session.getAttribute("myAppUserManager"); return myAppUser; } Despite the fact that I have the following in my context: <bean id="myAppUserManager" class="com.myapp.profile.MyAppUser" scope="session"/> This doesn't make any sense to me, the "myAppUser" bean is a bean that absolutely can never be null, and I need to be able to reference it from controllers, I don't need it in services or repositories, just controllers, but it doesn't seem to be getting stored in the session, the use case is extremely simple, but I haven't been able to get to the bottom of what's wrong, or come up with a good workaround

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  • using volatile keyword

    - by sap
    As i understand, if we declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. But in the following program both volatile and non-volatile variables are displaying same value. The volatile variable is not updated for the second thread. Can anybody plz explain this why testValue is not changed. class ExampleThread extends Thread { private int testValue1; private volatile int testValue; public ExampleThread(String str){ super(str); } public void run() { if (getName().equals("Thread 1 ")) { testValue = 10; testValue1= 10; System.out.println( "Thread 1 testValue1 : " + testValue1); System.out.println( "Thread 1 testValue : " + testValue); } if (getName().equals("Thread 2 ")) { System.out.println( "Thread 2 testValue1 : " + testValue1); System.out.println( "Thread 2 testValue : " + testValue); } } } public class VolatileExample { public static void main(String args[]) { new ExampleThread("Thread 1 ").start(); new ExampleThread("Thread 2 ").start(); } } output: Thread 1 testValue1 : 10 Thread 1 testValue : 10 Thread 2 testValue1 : 0 Thread 2 testValue : 0

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  • Autocomplete server-side implementation

    - by toluju
    What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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  • How to maintain base files for development environment central while allowing people to change their

    - by Ittai
    Hi, what I'd like to do is have files in a central location so that when I add people to my development team they can see the base version of these files but meanwhile have the ability for the rest of the team to work with their own local version. I know I can just put the files in source-control (we use Tortoiese-SVN) and have my team change the local versions but I'd rather not as the exclamation mark signaling the file has been changed and needs to be committed, quite frankly, irritates me greatly. I'll give two examples of what I mean: We use quite a few build.xml files which relate to a single properties files which contains many definitions. Some of them can be different between team-members (mainly temporary working directories) and I'd like a new team-member to have the ability to get the properties file with the base config but change it if they wish. Have the eclipse settings file in the SVN so that when a new team-member joins they can just retrieve the files from the server and have a base system running. If they wish they will be able to change some of these settings. Thanks, Ittai

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  • Grails , how do I get an object NOT to save

    - by user350325
    Hello I am new to grails and trying to create a form which allows a user to change the email address associated with his/her account for a site I am creating. It asks for the user for their current password and also for the new email address they want to use. If the user enters the wrong password or an invalid email address then it should reject them with an appropriate error message. Now the email validation can be done through constraints in grails, but the password change has to match their current password. I have implemented this check as a method on a service class. See code below: def saveEmail = { def client = ClientUser.get(session.clientUserID) client.email = params.email if(clientUserService.checkPassword(session.clientUserID , params.password) ==false) { flash.message = "Incorrect Password" client.discard() redirect(action:'changeEmail') } else if(!client.validate()) { flash.message = "Invalid Email Address" redirect(action:'changeEmail') } else { client.save(); session.clientUserID = null; flash.message = "Your email address has been changed, please login again" redirect(controller: 'clientLogin' , action:'index') } } Now what I noticed that was odd was that if I entered an invalid email then it would not save the changes (as expected) BUT if I entered the wrong password and a valid email then it would save the changes and even write them back into the database even though it would give the correct "invalid password" error message. I was puzzled so set break points in all the if/else if/else blocks and found that it was hitting the first if statement as expected and not hitting the others , so it would never come accross a call to the save() method, yet it was saved anyway. After a little research I came accross documentation for the discard() method which you can see used in the code above. So I added this but still no avail. I even tried using discard then reloading the client object from the DB again but still no dice. This is very frustrating and I would be grateful for any help, since I think that this should surely not be a complicated requirement!

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