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  • Calculated group-by fields in MongoDB

    - by Navin Viswanath
    For this example from the MongoDB documentation, how do I write the query using MongoTemplate? db.sales.aggregate( [ { $group : { _id : { month: { $month: "$date" }, day: { $dayOfMonth: "$date" }, year: { $year: "$date" } }, totalPrice: { $sum: { $multiply: [ "$price", "$quantity" ] } }, averageQuantity: { $avg: "$quantity" }, count: { $sum: 1 } } } ] ) Or in general, how do I group by a calculated field?

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  • how to add classes to build path in eclipse

    - by akshay
    I have used the folllowing steps to add classes to my build path still i am geting errors as import not resolved.I had followed the following steps. Select Create New Folder and name it TpmWebUIClasses. Click the Advanced button and select the Link to folder in the file system check box. Browse for to the folder where you have copied the classes Make sure the selected folder is listed and then click OK. How can i resolve the error?

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  • XML parse file from HTTP

    - by Travis
    I have an XML file located at a location such as http://example.com/test.xml I'm trying to parse the XML file to use it in my program with xPath like this but it is not working. Document doc = builder.parse(new File(url)); How can I get the XML file?

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  • Headless build of eclipse features - PDE Tools or Buckminster?

    - by Max
    I am trying to set up a headless build for a big eclipse feature, containing other features and plugins. As some needed plugins are generated using GMF and EMF, the build workflow must be something like this: SVN Check-out Invoke Generation Run Tests Build all Publish update-site Over the last couple of weeks, i played around with PDE Headless Build and Buckminster. Anyhow i still got problems with both and can't decide on which i should spent my effort. So what would you prefer? What experience you made? Anybody out there who needed to set up a similiar workflow before? Thank you for all answers :)

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  • Algorithm for redirecting the traffic

    - by TechGeeky
    I was going through the interview questions and found out the below question which I am not able to answer it. Can anyone provide some sort of algorithm for this problem how can I solve it? There are a cluster of stateless servers all serving the same pages. The servers are hosting 5 web pages- p1.html, p2.html, p3.html, p4.html and p5.html p1.html just redirects users to the other 4 pages Requests to p1.html should result in 10% of users being redirected to p2.html, 5% of users redirected to p3.html, 20% of users redirected to p4.html, and 65% of users redirected to p5.html. Users do not need to stick to the page they are first redirected to. They could end up on a different page with every request to p1.html Write a function/pseudocode that would be invoked with every request to p1.html and redirect the correct percentage of users to the correct page. Any suggestions will be of great help.

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  • In this example, would Customer or AccountInfo properly be the entity group parent?

    - by Badhu Seral
    In this example, the Google App Engine documentation makes the Customer the entity group parent of the AccountInfo entity. Wouldn't AccountInfo encapsulate Customer rather than the other way around? Normally I would think of an AccountInfo class as including all of the information about the Customer. import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; import com.google.appengine.api.datastore.Key; import com.google.appengine.api.datastore.KeyFactory; @PersistenceCapable public class AccountInfo { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; public void setKey(Key key) { this.key = key; } } // ... KeyFactory.Builder keyBuilder = new KeyFactory.Builder(Customer.class.getSimpleName(), "custid985135"); keyBuilder.addChild(AccountInfo.class.getSimpleName(), "acctidX142516"); Key key = keyBuilder.getKey(); AccountInfo acct = new AccountInfo(); acct.setKey(key); pm.makePersistent(acct);

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  • How to schedule an alarm so that the intent is broadcast everytime the date changes?

    - by rogerstone
    I want to schedule an alarm which throws an intent when the date changes. I know that this would do this the job alarms.setRepeating(AlarmManager.RTC_WAKEUP,triggerAtTime, interval,alarmIntent); But what is confusing me is what to put in the triggerAtTime and the interval.It says System.currentTimeMillis() timebase. I might be installing the app on any day so the TriggerAtTime should be midnight of that day and the interval would be 24 hours from there on. How can I acheive this.Can someone tell me what to put in TriggerAtTime and interval in the required format. Thanks

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  • Defining tokens at runtime

    - by Peter Crenshaw
    I want to write a parser for EDIFACT messages with JavaCC. My problem is that I cannot define all terminal symbols before parsing a message because at the begining of each message there is a so called "Advice Segment" ("UNA" Segment) which defines things like element seperator symbol, escape symbol, segment terminator symbol and decimal notation (e.g. '.' or ','). So I think/guess the production rules need some kind of variables which must be set at runtime during parsing. Can this be done with JavaCC and if so how? Or is there another way I am missing?

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  • Threadsafe way of exposing keySet()

    - by Jake
    This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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  • getSystemResourceAsStream() returns null

    - by Hitesh Solanki
    Hiii... I want to get the content of properties file into InputStream class object using getSystemResourceAsStream(). I have built the sample code. It works well using main() method,but when i deploy the project and run on the server, properties file path cannot obtained ... so inputstream object store null value. Sample code is here.. public class ReadPropertyFromFile { public static Logger logger = Logger.getLogger(ReadPropertyFromFile.class); public static String readProperty(String fileName, String propertyName) { String value = null; try { //fileName = "api.properties"; //propertyName = "api_loginid"; System.out.println("11111111...In the read proprty file....."); // ClassLoader loader = ClassLoader.getSystemClassLoader(); InputStream inStream = ClassLoader.getSystemResourceAsStream(fileName); System.out.println("In the read proprty file....."); System.out.println("File Name :" + fileName); System.out.println("instream = "+inStream); Properties prop = new Properties(); try { prop.load(inStream); value = prop.getProperty(propertyName); } catch (Exception e) { logger.warn("Error occured while reading property " + propertyName + " = ", e); return null; } } catch (Exception e) { System.out.println("Exception = " + e); } return value; } public static void main(String args[]) { System.out.println("prop value = " + ReadPropertyFromFile.readProperty("api.properties", "api_loginid")); } }

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  • Tomcat Postgres Connection

    - by user191207
    Hi, I'm using a singleton class for a PostgresSQL connection inside a servelet. The problem is that once it is open it works for a while (I guess until some timeout), and then it starts throwing a I/O exception. Any idea what is happening to the singleton class inside Tomcat VM? Thanks

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  • How to set default values to all wrong or null parameters of method?

    - by Roman
    At the moment I have this code (and I don't like it): private RenderedImage private RenderedImage getChartImage (GanttChartModel model, String title, Integer width, Integer height, String xAxisLabel, String yAxisLabel, Boolean showLegend) { if (title == null) { title = ""; } if (xAxisLabel == null) { xAxisLabel = ""; } if (yAxisLabel == null) { yAxisLabel = ""; } if (showLegend == null) { showLegend = true; } if (width == null) { width = DEFAULT_WIDTH; } if (height == null) { height = DEFAULT_HEIGHT; } ... } How can I improve it? I have some thoughts about introducing an object which will contain all these parameters as fields and then, maybe, it'll be possible to apply builder pattern. But still don't have clear vision how to implement that and I'm not sure that it's worth to be done. Any other ideas?

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  • Refreshing a JPA result list which is bound with a jTable

    - by exhuma
    First off, I hage to write this on my mobile. But I'll try to format it properly. In Netbeans I created a jTable and bound it's values to a JPA result set. This works great. The qery contains a param which i set in the pre-create box of the "query result" component. So just before netbeans creates the query result i write this: myQuery.setParameter("year", "1997"); This works fine. Now, I have an event handler which is supposed to change the param and display the new values in the table. So I do this: myQuery.setParameter("year", "2005"); myResultList.clear(); myResultList.addAll(myQuery.getResultList()); jTable1.updateUI(); This works, but it feels wrong to me. Note: the result set is bound to the table. So I was hoping there was something like this: myQuery.setParameter("year", "2005"); myResultList.refresh(); Is there something like this?

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  • Using an empty keystore password used to be possible?

    - by TomTasche
    When signing an apk after a long break from Android development I was surprised that I'm no longer able to enter an empty keystore password to unlock it. Is it just me or has this been possible before? If so, when did that change and how can I manage to unlock the keystore anyway? Some background: maybe I'm just crazy and didn't use an empty password for the keystore before, but the one and only possible password that I could have been using instead doesn't work either (I swear, there's no chance I'd have used another password!).

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  • GWT: stange import collision error in visualisation api

    - by parag_
    hi, I'm attempting to add two charts to a gwt page using the visualization api, but for some strange and inexplicable reason, eclipse claims that the following two imports are colliding - which makes no sense to me. In the methods where i am calling them, I have even tried using the fully qualified names, but that doesnt seem to help either. Any idea what may be going on ? import com.google.gwt.visualization.client.visualizations.Table.Options; import com.google.gwt.visualization.client.visualizations.LineChart.Options;

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  • why it throws index out of bounds exception??

    - by Johanna
    Hi I want to use merge sort for sorting my doubly linked list.I have created 3 classes(Node,DoublyLinkedList,MergeSort) but it will throw this exception for these lines: 1.in the getNodes method of DoublyLinkedList---> throw new IndexOutOfBoundsException(); 2.in the add method of DoublyLinkedList-----> Node cursor = getNodes(index); 3.in the sort method of MergeSort class------> listTwo.add(x,localDoublyLinkedList.getValue(x)); 4.in the main method of DoublyLinkedList----->merge.sort(); this is my Merge class:(I put the whole code for this class for beter understanding) public class MergeSort { private DoublyLinkedList localDoublyLinkedList; public MergeSort(DoublyLinkedList list) { localDoublyLinkedList = list; } public void sort() { if (localDoublyLinkedList.size() <= 1) { return; } DoublyLinkedList listOne = new DoublyLinkedList(); DoublyLinkedList listTwo = new DoublyLinkedList(); for (int x = 0; x < (localDoublyLinkedList.size() / 2); x++) { listOne.add(x, localDoublyLinkedList.getValue(x)); } for (int x = (localDoublyLinkedList.size() / 2) + 1; x < localDoublyLinkedList.size(); x++) { listTwo.add(x, localDoublyLinkedList.getValue(x)); } //Split the DoublyLinkedList again MergeSort sort1 = new MergeSort(listOne); MergeSort sort2 = new MergeSort(listTwo); sort1.sort(); sort2.sort(); merge(listOne, listTwo); } public void merge(DoublyLinkedList a, DoublyLinkedList b) { int x = 0; int y = 0; int z = 0; while (x < a.size() && y < b.size()) { if (a.getValue(x) < b.getValue(y)) { localDoublyLinkedList.add(z, a.getValue(x)); x++; } else { localDoublyLinkedList.add(z, b.getValue(y)); y++; } z++; } //copy remaining elements to the tail of a[]; for (int i = x; i < a.size(); i++) { localDoublyLinkedList.add(z, a.getValue(i)); z++; } for (int i = y; i < b.size(); i++) { localDoublyLinkedList.add(z, b.getValue(i)); z++; } } } and just a part of my DoublyLinkedList: private Node getNodes(int index) throws IndexOutOfBoundsException { if (index < 0 || index > length) { throw new IndexOutOfBoundsException(); } else { Node cursor = head; for (int i = 0; i < index; i++) { cursor = cursor.getNext(); } return cursor; } } public void add(int index, int value) throws IndexOutOfBoundsException { Node cursor = getNodes(index); Node temp = new Node(value); temp.setPrev(cursor); temp.setNext(cursor.getNext()); cursor.getNext().setPrev(temp); cursor.setNext(temp); length++; } public static void main(String[] args) { int i = 0; i = getRandomNumber(10, 10000); DoublyLinkedList list = new DoublyLinkedList(); for (int j = 0; j < i; j++) { list.add(j, getRandomNumber(10, 10000)); MergeSort merge = new MergeSort(list); merge.sort(); System.out.println(list.getValue(j)); } } PLEASE help me thanks alot.

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  • Is dependency injection only for service type objects and singletons? (and NOT for gui?)

    - by sensui
    I'm currently experimenting with the Google's guice inversion of control container. I previously had singletons for just about any service (database, active directory) my application used. Now I refactored the code: all the dependencies are given as parameters to constructors. So far, so good. Now the hardest part is with the graphical user interface. I face this problem: I have a table (JTable) of products wrapped in an ProductFrame. I give the dependencies as parameters (EditProductDialog). @Inject public ProductFrame(EditProductDialog editProductDialog) { // ... } // ... @Inject public EditProductDialog(DBProductController productController, Product product) { // ... } The problem is that guice can't know what Product I have selected in the table, so it can't know what to inject in the EditProductDialog. Dependency Injection is pretty viral (if I modify one class to use dependency injection I also need to modify all the other classes it interacts with) so my question is should I directly instantiate EditProductDialog? But then I would have to pass manually the DBProductController to the EditProductDialog and I will also need to pass it to the ProductFrame and all this boils down to not using dependency injection at all. Or is my design flawed and because of that I can't really adapt the project to dependecy injection? Give me some examples of how you used dependency injection with the graphical user interface. All the examples found on the Internet are really simple examples where you use some services (mostly databases) with dependency injection.

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  • Concurrent Programming:Should I write a sequential program first, then add thread safety?

    - by evthim
    I'm working on a project where we have to create a number of threads(actual number will be inputted in by testers (TA's)). I'm having trouble not only with the programming but also with the design, I can't wrap my head around all of the threads that will be invoked and where I might cause errors. The project is due soon so I don't want to waste time on this if it'll actually set me back, but I was wondering if I should write the program like only one thread will be running and everything should be sequential and then later go back and try to add the thread safety parts of the code? Would that take twice the original amount of time? Project Description: Note:I'm going to be as vague as possible so I don't violate any honor codes, sorry :( your program should accept n number of objectA threads, m number of objectB threads, and r number of objectC objectB threads interact with code in objectA. objectA threads interact with code in objectB and objectC objectB and objectC don't directly interact, but do so indirectly through objectA -ex: objectB needs something from objectA. objectA gets the result for that something by calling objectC my confusion stems mostly from the fact that all of this interactions will be done by m+n threads and there are various restrictions throughout the descriptions, like objectB can request something from objectA, and objectA has to wait for objectC to finish that something before returning it to objectB. Also each objectA thread can only work on one instruction from objectB at a time, etc. etc. I just want to know if I write the code so that there is only 1 objectA, 1 objectB and 1 object C, can I go back and easily modify it so that those 1's can be changed to m, n and r? Sorry again, if my description is a little bit confusing.

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  • How to call superconstructor in a neat way

    - by sandis
    So here is my code: public MyClass (int y) { super(y,x,x); //some code } My problem is that in this case i want to generate a 'x' and sent to the super constructor. However the call to the superconstructor must be the first line in this constructor. Of course I could do something like this: int x; { x = generateX(); } But this feels ugly, and then the code will run no matter what constructor I use, which feels not so nice. Right now I am consider encapsulating my whole object in another object that only calculates x and then starts this object. Is this the best approach?

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  • JButton Image Ignoring GridBagConstraints

    - by daemor
    I am working on an application and have a screen that needs to have elements (namely some custom JButtons) appear and disappear based on a user selection. However for some reason, when I add these buttons to their pane, the buttton image goes to the top corner, and leaves the text in the center, completely ignoring GridBagConstraints. I am completely stumped on this one as I have done this same exact thing dozens of times earlier in the program without any issues. Here is an image of the problem: The problem is in this method here, and occurs down towards the bottom. public void init(){ contentPane.removeAll(); // Setup jlabels JLabel countyLabel = new JLabel("County"); countyLabel.setFont(new Font("Times New Roman", Font.PLAIN, 18)); JLabel measureByLabel = new JLabel("Measure By: "); measureByLabel.setFont(new Font("Times New Roman", Font.PLAIN, 18)); String[] countyChoices = {"Washtenaw", "Oakland", "Livingston"}; // setup components JComboBox<String> countyCombo = new JComboBox<String>(countyChoices); // place baseComponents c.weightx = 0.5; c.weighty = 0.5; c.gridx = 0; c.gridy = 0; c.anchor = GridBagConstraints.NORTH; contentPane.add(countyLabel, c); c.gridx = 2; contentPane.add(countyCombo, c); c.gridy = 1; c.gridx = 0; contentPane.add(trenchButton, c); c.gridx = 2; contentPane.add(bedButton, c); c.gridy = 2; c.gridx = 1; contentPane.add(systemSelection, c); c.gridy = 3; c.gridx = 0; contentPane.add(lengthButton, c); c.fill = GridBagConstraints.BOTH; c.gridwidth = 4; c.gridy = 4; c.gridx = 0; contentPane.add(choicePane, c); GridBagConstraints con = new GridBagConstraints(); con.weightx = 0.5; con.weighty = 0.5; con.gridx = 0; con.gridy = 0; choicePane.add(lengthButton, c); // revalidate and repaint choicePane.revalidate(); choicePane.repaint(); contentPane.revalidate(); contentPane.repaint(); } I have tried doing this in separate methods, the button looks fine when added to the contentPane, the pane is for sure set to gridbagconstraints as I used the expression JPanel choicePane = new JPanel(new GridBagLayout()) to initialize it.

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  • Scanner cuts off my String after about 2400 characters

    - by Ventrue
    I've got some very basic code like while (scan.hasNextLine()) { String temp = scan.nextLine(); System.out.println(temp); } where scan is a Scanner over a file. However, on one particular line, which is about 6k chars long, temp cuts out after something like 2470 characters. There's nothing special about when it cuts out; it's in the middle of the word "Australia." If I delete characters from the line, the place where it cuts out changes; e.g. if I delete characters 0-100 in the file then Scanner will get what was previously 100-2570. I've used Scanner for larger strings before. Any idea what could be going wrong?

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