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  • Java: ListA.addAll(ListB) fires NullPointerException?

    - by HH
    The err part is Capitalized in the code, it also comes in foreaching. Because of the abstract list, it cannot be initialized, declaration is in a static field. The lists have the same type. import java.util.*; public class Test { public static final List<String> highPrio = Arrays.asList("*","/"); public static List<String> ops; public static void main(String[] args) { //ERROR HERE, why do it throw nullPointer? ops.addAll(highPrio); for(String s : ops) { System.out.println(s); } } }

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  • Efficient retrieval of lists over WebServices

    - by Chris
    I have a WCF WebService that uses LINQ and EF to connect to an SQL database. I have an ASP.NET MVC front end that collects its data from the webservice. It currently has functions such as List<Customer> GetCustomers(); As the number of customers increases massively the amount of data being passed increases also reducing efficiency. What is the best way to "page data" across WebServices etc. My current idea is to implement a crude paging system such as List<Customer> GetCustomers(int start, int length); This, however, means I would have to replicate such code for all functions returning List types. It is unfortunate that I cannot use LINQ as it would be much nicer. Does anyone have any advice or ideas of patterns to implement that would be "as nice as possible" Thanks

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  • walking list in KDB/kernel debugger

    - by user291849
    I need to walk a link list in the kernel debugger. How can I determine the head pointer and walk the list? I have a listing and can find the address and location in the code where I check to see if I have a head, so I know the specific code location and address. But not sure how to determine the pointer or how to determine the next element and pointer on the list.

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  • Allow users to enter a variable length list of items in asp.net form

    - by EJB
    I need to let my users enter a variable length list of items into something that looks like a grid view (or a series of standard text boxes stacked vertically). Each item could be a few characters or a few hundred characters long, and I just want them to enter a "sentence", and then tab to the next row, and always having another blank one ready to go at the bottom of the list. I don't want to save any data to my SQL Server DB until they enter the entire list and then click on a "save all" button. When they hit the "save all" button they will be given a preview screen where the data will be presented as standard HTML ordered list. If they confirm/save, then each row of the grid will then be saved as a separate row into my SQL Server database (with an index to remember the order). What ASP.Net (or Jquery/javascript) UI control would be the best to use in this situation?

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  • Displaying a list of items vertically in a table instead of horizonally

    - by MichaelMM
    I have a list of items sorted alphabetically: list = [a,b,c,d,e,f,g,h,i,j] I'm able to output the list in an html table horizonally like so: | a , b , c , d | | e , f , g , h  | | i  , j  ,    ,     | What's the algorithm to create the table vertically like this: | a , d , g , j | | b , e , h ,   | | c , f  ,  i  ,  | I'm using python, but your answer can be in any language or even pseudocode. Thanks

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  • Selecting a sequence of elements from the IList

    - by KhanS
    I have a IList. where the object PersonDetails consists of the persons name, address and phone number. The list consists of more than 1000 person details. I would like to display 50 PersonDetails per page. Is there a way to select only 50 elements from the list, and return them. For example. myList.select(1,50) myList.select(51, 100) I am able to select only first 50 by using. myList.Take(50); The entire list is at the wcf service, and i would like to get only fifty elements at a time.

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  • A question about comparing List<T>

    - by Varyanica
    i have two lists: List<comparerobj> list_c = new List<comparerobj>(); List<comparerobj> list_b = new List<comparerobj>(); i'm filling lists somehow then i'm trying to find elements in list_b which list_c doesnt contain: foreach (comparerobj b in list_b) { bool lc = !list_c.Contains(b); if (lc != true) { data.Add(b); } } but for any b i'm getting that lc = true. what am i doing wrong?

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  • Easiest way to merge two List<T>s

    - by Chris McCall
    I've got two List<Name>s: public class Name { public string NameText {get;set;} public Gender Gender { get; set; } } public class Gender { public decimal MaleFrequency { get; set; } public decimal MaleCumulativeFrequency { get; set; } public decimal FemaleCumulativeFrequency { get; set; } public decimal FemaleFrequency { get; set; } } If the NameText property matches, I'd like to take the FemaleFrequency and FemaleCumulativeFrequency from the list of female Names and the MaleFrequency and MaleCumulativeFrequency values from the list of male Names and create one list of Names with all four properties populated. What's the easiest way to go about this in C# using .Net 3.5?

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  • Increase the length of Xcode's "recent project" list?

    - by Bogatyr
    I switch in Xcode between working on a lot of different projects frequently (some I'm actively working on, some are old projects where I'm looking up code I want to re-use or quote in SO answers :)), so that part of my "working set" of projects invariably ends up falling off the recent project list. I do use finder tabs for the full working set of current project folders, but I really like the fast switching available using the recent projects list. Is there a way to increase the length of this list so that I can see more recently opened projects?

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  • Join data from two Lists into one object

    - by Petr Mensik
    I ran into following situation and I am wondering about best solution. Let's say I have List<Object1> and List<Object2>, these lists are result of two separated queries. Both of them have the same size and there is relationship 1:1 between elements in the lists based on ID. I know that best solution would be fetching data in one DB query but that's possible right now. So my question is, what is the best way to join these lists into let's say List<Object3>?

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  • Group Objects by Common Key

    - by Marshmellow1328
    I have a list of Customers. Each customer has an address and some customers may actually have the same address. My ultimate goal is to group customers based on their address. I figure I could either put the customers in some sort of list-based structure and sort on the addresses, or I could drop the objects into some sort of map that allows multiple values per key. I will now make a pretty picture: List: A1 - C1, A1 - C2, A2 - C3, A3 - C4, A3 - C5 Map: A1 A2 A3 C1 C3 C4 C2 C5 Which option (or any others) do you see as the best solution? Are there any existing classes that will make development easier?

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  • QT List of Callbacks

    - by Talguy
    I am trying to make a real-time data collection application that has timed task. Each task can have a different or the same update period. I would like to store the task with the common update period in a list where I can iterate through it and call the function that I registered in the list. How would I go about adding callbacks to a data structure like a list or vector? Can I store slots in them?

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  • How do I select every 6th element from a list (using Linq)

    - by iDog
    Hi, I've got a list of 'double' values. I need to select every 6th record. It's a list of coordinates, where I need to get the minimum and maximum value of every 6th value. List of coordinates (sample): [2.1, 4.3, 1.0, 7.1, 10.6, 39.23, 0.5, ... ] with hundrets of coordinates. Result should look like: [x_min, y_min, z_min, x_max, y_max, z_max] with exactly 6 coordinates. Following code works, but it takes to long to iterate over all coordinates. I'd like to use Linq instead (maybe faster?) for (int i = 0; i < 6; i++) { List<double> coordinateRange = new List<double>(); for (int j = i; j < allCoordinates.Count(); j = j + 6) coordinateRange.Add(allCoordinates[j]); if (i < 3) boundingBox.Add(coordinateRange.Min()); else boundingBox.Add(coordinateRange.Max()); } Any suggestions? Many thanks! Greets!

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  • How to store and synchronize a big list of strings

    - by Joel
    I have a large database table in SQLExpress on Windows, with a particular field of interest 'code'. I have an Apache web server with MySQL on Linux. The web application on the Linux box needs access to the list of all codes. The only thing it will use the list for is checking for the existence of a given code. Having the Linux server call out to the Windows server is impractical as the Windows server is behind a NAT'ed office internet connection, and it may not always be accessible. I have set it so the Windows server will push the list of codes to the web server by means of a simple HTTP POST request. However, at this point I have not implemented the storage of the codes on the Linux box. Should I store them in a MySQL table with a single field 'code'? Then I get fast indexed lookups O(1), however I think synchronization will be an issue - given an updated list of codes, pushed from the Windows box, how would I optimally synchronize the list with the database? TRUNCATE, followed by INSERT? Should I instead store them in a flat file? Then I have O(n) look up time rather than O(1). Additionally an extra constant-time overhead too, as I will be processing the file in Ruby. However, synchronization is easy - simply replace the file.

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  • Python - read numbers from text file and put into list

    - by user1647372
    So like the title says im starting to learn some python and im having trouble picking up on this technique. What I need to accomplish is to read in some numbers and store them in a list. The text file looks like the following: 0 0 3 50 50 100 4 20 Basically these are coordinates and directions to be used for python's turtle to make shapes. I got that part down the only problem is getting them in a correct format. So what I can not figure out is how to get those numbers from the file into [ [0, 0, 3, 50], [50, 100, 4, 20] ] A list, with each four coordinates being a list in that one big list. Heres my attempt but it as I said I need some help - thank you. polyShape=[] infile = open(name,"r") num = int(infile.readline(2)) while num != "": polyShape.append(num) num = int(infile.readline(2)) infile.close()

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  • Choosing randomly all the elements in the the list just once

    - by Dalek
    How is it possible to randomly choose a number from a list with n elements, n time without picking the same element of the list twice. I wrote a code to choose the sequence number of the elements in the list but it is slow: >>>redshift=np.array([0.92,0.17,0.51,1.33,....,0.41,0.82]) >>>redshift.shape (1225,) exclude=[] k=0 ng=1225 while (k < ng): flag1=0 sq=random.randint(0, ng) while (flag1<1): if sq in exclude: flag1=1 sq=random.randint(0, ng) else: print sq exclude.append(sq) flag1=0 z=redshift[sq] k+=1 It doesn't choose all the sequence number of elements in the list.

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  • Java Util Linked List - how to find next?

    - by drozzy
    When using Java LinkedList how do you find out the element's next or previous relationships? I mean, in a regular linked list I would do something like this: Node node1 = new Node(); Node node2 = new Node(); LinkedList list = new LinkedList(); list.add(node1); list.add(node2); //then my node1 will know who it's next is: assertEquals(node2, node1.next()); But in Java's LinkedList, the data does not seem to be modified. So how do I actually find out who the "next" (or "previous" in the case of doubly-linked lists) element is?

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  • Managing a list of threads

    - by Satanlike
    Hi, I have an application (.Net 3.5) which creates threads to write something to the database so that the GUI does not block. All created threads are added to a list, so that I can wait (Thread.Join) for each thread when the application is closed (maybe not all threads are finished when the application is closed, so the app must wait for them). Because of the list I get some serious problems if there are too many threads created (OutOfMemoryException). I tried removing finished threads from the list, but somehow that didn't work. Are there better ways to manage a list of threads, so I can remove them once they are finished?

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  • Folding a list in F#

    - by bytebuster
    I have a pretty trivial task but I can't figure out how to make the solution prettier. The goal is taking a List and returning results, based on whether they passed a predicate. The results should be grouped. Here's a simplified example: Predicate: isEven Inp : [2; 4; 3; 7; 6; 10; 4; 5] Out: [[^^^^]......[^^^^^^^^]..] Here's the code I have so far: let f p ls = List.foldBack (fun el (xs, ys) -> if p el then (el::xs, ys) else ([], xs::ys)) ls ([], []) |> List.Cons // (1) |> List.filter (not << List.isEmpty) // (2) let even x = x % 2 = 0 let ret = [2; 4; 3; 7; 6; 10; 4; 5] |> f even // expected [[2; 4]; [6; 10; 4]] This code does not seem to be readable that much. Also, I don't like lines (1) and (2). Is there any better solution?

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  • Convert list to double[][] in C#3.0

    - by Newbie
    Given List<double> x1 = new List<double> { -0.2718, -0.2240, -0.1275, -0.0810, 0.0349, -0.5067, 0.0094, -0.4404, -0.1212 }; List<double> x2 = new List<double> { 0.0330, -0.6463, 0.1226, -0.3304, 0.4764, -0.4159, 0.4209, -0.4070, -0.2090 }; How can I make as double[][] X at runtime(programatically). I mean to say if the output I get if I run double[][] X = { new double[] { -0.2718, -0.2240, -0.1275, -0.0810, 0.0349, -0.5067, 0.0094, -0.4404, -0.1212 }, new double[] { 0.0330, -0.6463, 0.1226, -0.3304, 0.4764, -0.4159, 0.4209, -0.4070, -0.2090 } }; Using C#3.0 Thanks

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  • How to assign variable dynamically to php list function

    - by ravisoni
    What I am doing that I want to generate a list based on how many items are in an array, so I have counted the items and loop over them, create a number based var and construct a string $var which contains $a1,$a2.... and assigns the $var to list list($var) and tried to access $a1 but it gives me the error "Undefined variable: a1" Is there any other way to do it? Here is my code: $arr = array('1','2','3'); $listsize = count($arr); $var=''; for($i=1;$i<=$listsize;$i++){ $var.='$a'.$i; if($i!=$listsize){ $var.=','; } } list($var) = $arr; echo $a1;

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  • Removing words from a file

    - by user1765792
    I'm trying to take a regular text file and remove words identified in a separate file (stopwords) containing the words to be removed separated by carriage returns ("\n"). Right now I'm converting both files into lists so that the elements of each list can be compared. I got this function to work, but it doesn't remove all of the words I have specified in the stopwords file. Any help is greatly appreciated. def elimstops(file_str): #takes as input a string for the stopwords file location stop_f = open(file_str, 'r') stopw = stop_f.read() stopw = stopw.split('\n') text_file = open('sample.txt') #Opens the file whose stop words will be eliminated prime = text_file.read() prime = prime.split(' ') #Splits the string into a list separated by a space tot_str = "" #total string i = 0 while i < (len(stopw)): if stopw[i] in prime: prime.remove(stopw[i]) #removes the stopword from the text else: pass i += 1 # Creates a new string from the compilation of list elements # with the stop words removed for v in prime: tot_str = tot_str + str(v) + " " return tot_str

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