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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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  • 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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  • Need help receiving ByteArray data

    - by k80sg
    Hi folks, I am trying to receive byte array data from a machine. It sends out 3 different types of data structure each with different number of fields which consist of mostly int and a few floats, and byte sizes, the first being 320 bytes, 420 for the second type and 560 for the third. When the sending program is launched, it fires all 3 types of data simultaneouly with an interval of 1 sec. Example: Sending order: Pack1 - 320 bytes 1 sec later Pack2 - 420 bytes 1 sec later Pack3 - 560 bytes 1 sec later Pack1 - 320 bytes ... .. . How do I check the incoming byte size before passing it to: byte[] handsize = new byte[bytesize]; as the data I receive are all out of order, for instance using the following the read all int: System.out.println("Reading data in int format:" + " " + datainput.readInt()); I get many different sets of values whenever I run my prog although with some valid field data but they are all over the place. I am not too sure how exactly should I do it but I tried the following and apparently my data fields are not receiving in correct sequence: BufferedInputStream bais = new BufferedInputStream(requestSocket.getInputStream()); DataInputStream datainput = new DataInputStream(bais); byte[] handsize = new byte[560]; datainput.readFully(handsize); int n = 0; int intByte[] = new int[140]; for (int i = 0; i < 140 ; i++) { System.out.println("Reading data in int format:" + " " + datainput.readInt()); intByte[n] = datainput.readInt(); n = n + 1; System.out.println("The value in array is:" + intByte[0]); System.out.println("The value in array is:" + intByte[1]); System.out.println("The value in array is:" + intByte[2]); System.out.println("The value in array is:" + intByte[3]); Also from the above code, the order of the values printed out with System.out.println("Reading data in int format:" + " " + datainput.readInt()); and System.out.println("The value in array is:" + intByte[0]); System.out.println("The value in array is:" + intByte[1]); are different. Any help will be appreciated. Thanks

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  • How to use BeanTreeView?

    - by joseph
    Hello. I have read through whole platform.netbeans.org and I do not find how to add some instance to existing children. I can add static array of diagrams(created in addNotify()), but how to add new Diagram object to the Children? I want to add it from an action that I will create(not included in code). See the code: public class ExploirerTopComponent extends TopComponent implements ExplorerManager.Provider { ... ... ... public ExploirerTopComponent() { ... ... associateLookup (ExplorerUtils.createLookup(mgr, getActionMap())); mgr.setRootContext(new MyProjects());// setDisplayName ("Projects explorer"); } public class MyProjects extends AbstractNode { public MyProjects(MainProject obj) { super (new ProjectsChildren(), Lookups.singleton(obj)); setDisplayName ( obj.getName()); } public MyProjects() { super (new ProjectsChildren()); setDisplayName ("My projects"); } } . public class ProjectsChildren extends Children.Keys{ public ProjectsChildren() { } @Override protected Node[] createNodes(Object o) { MainProject obj = (MainProject) o; return new Node[] { new MyDiagrams() }; } @Override protected void addNotify() { Diagram[] d = new Diagram[3]; for (int i = 0; i < pr.length; i++) { pr[i] = new Diagram("digram"); } setKeys (pr); } }

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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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  • Publishing selection in eclipse RCP

    - by Stuart
    I'm writing an RCP application plug-in. I want to make a set of objects the global selection from a IHandler but this can be triggered from other views out of my control - it is possible that these do not have an ISelectionProvider. Is it possible to publish a selection to the eclipse selection service without going through some view site?

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  • Ant build.xml requires user input, but Eclipse has no tty

    - by carneades
    I'm trying to better integrate Eclipse with my build.xml. My build file calls GNU Make for the native portion of the program, and the Makefile uses sudo to movethe compiled libs into system path. Unfortunately that requires entering a password, and Eclipse's terminal doesn't accept user input. So the result from running the build in eclipse is: [exec] sudo: no tty present and no askpass program specified [exec] make: *** [install] Error 1 Any way around this problem? Can the ant build be elevated to root some other way?

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  • ListView items not responding to tap

    - by Justin Williams
    I'm just getting my feet wet with Android and have built a UI that contains a TabHost with three tabs. Each tab is powered by its own Activity. The first Tab contains a listview with a prepopulated set of rows and is built from a custom ArrayAdapter. The problem I'm running into is that none of the ListView rows are tappable. In other words, when I tap on them there is no orange selection. If I use the scroll ball on my Nexus One it will select, but any touch gestures don't seem to be responding. All the UI is being handled using XML files with a main.xml housing the TabHost - LinearLayout - TabWidget/FrameLayout and a nearby_activity.xml file containing my ListView UI <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <TextView android:id="@+id/android:empty" android:layout_width="fill_parent" android:layout_height="fill_parent" android:text="@string/nearby_no_events" /> <ListView android:id="@android:id/list" android:layout_width="fill_parent" android:layout_height="0dip" android:layout_weight="1.0" android:choiceMode="multipleChoice" android:divider="#d9d9d9" android:dividerHeight="1px" android:cacheColorHint="#eee" /> </LinearLayout> And the relevant code from my Activity that is set to show in the selected tab. public class NearbyActivity extends ListActivity { private ArrayList<Event> m_events = null; private EventAdapter m_adapter = null; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.nearby_activity); getEvents(); this.m_adapter = new EventAdapter(this, R.layout.eventrow, m_events); setListAdapter(this.m_adapter); } private void getEvents() { m_events = new ArrayList<Event>(); for (int i = 0; i < 100 ; i++) { Event e = new Event(); e.setEventName("Event " + i); e.setVenueName("Staples Center"); e.setStartDate(new Date()); m_events.add(e); } } private class EventAdapter extends ArrayAdapter<Event> { private ArrayList<Event> items; public EventAdapter(Context context, int textViewResourceId, ArrayList<Event> items) { super(context, textViewResourceId, items); this.items = items; } @Override public View getView (int position, View convertView, ViewGroup parent) { View v = convertView; if (v == null) { LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE); v = vi.inflate(R.layout.eventrow, null); } Event e = items.get(position); if (e != null) { TextView nameText = (TextView)v.findViewById(R.id.eventName); TextView venueNameText = (TextView)v.findViewById(R.id.venueName); if (nameText != null) { nameText.setText(e.getEventName()); } if(venueNameText != null) { venueNameText.setText(e.getVenueName()); } } return v; } } } My listview row's are populated by an XML file as well. <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="?android:attr/listPreferredItemHeight" android:orientation="vertical" android:padding="4dip"> <TextView android:id="@+id/eventName" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:inputType="text" android:singleLine="true" android:ellipsize="marquee" android:textSize="18sp" android:textColor="#000" /> <TextView android:id="@+id/venueName" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@id/eventName" android:layout_alignParentBottom="true" android:layout_marginRight="55dip" android:singleLine="true" android:ellipsize="end" android:scrollHorizontally="true" android:textSize="13sp" android:textColor="#313131" android:layout_alignWithParentIfMissing="true" android:gravity="center_vertical" /> </RelativeLayout> Thanks for any help you can offer.

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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 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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  • 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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  • 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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