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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • List of running minimum values

    - by scarle88
    Given a sorted list of: new []{1, 2, -1, 3, -2, 1, 1, 2, -1, -3} I want to be able to iterate over the list and at each element return the smallest value iterated so far. So given the list above the resultant list would look like: 1 1 -1 -1 -2 -2 -2 -2 -2 -3 My rough draft code looks like: var items = new []{1, 2, -1, 3, -2, 1, 1, 2, -1, -3}; var min = items.First(); var drawdown = items.Select(i => { if(i < min) { min = i; return i; } else { return min; } }); foreach(var i in drawdown) { Console.WriteLine(i); } But this is not very elegant. Is there an easier to read (linq?) way of doing this? I looked into Aggregate but it seemed to be the wrong tool. Ultimately the list of items will be very long, in the many thousands. So good performance will be an issue to.

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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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  • List in C# - passing multiple entries as a single object

    - by Karthick
    Hi, I have a method (C#) public void MethodName(List<Order> Order, int ID) I need to pass this to a main page, in which i know to pass integer value to ID, am not able to pass multiple items in a single list. The List order should have two number entries, (ie. Order.number1 and Order.number2) How should i pass a single list as a parameter to this method containing multiple entries of number1 and 2, so that i can loop thro' and find it. Thanks.

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  • sort list(of string()) using a variable index into string() as key - vb.net

    - by tullynyguy
    I have a List(of String()). I have written a custom comparer (implements IComparer(of string)) to do an alphanumeric sort. Is there a way to sort the List using a given index to determine which position in the String() to sort by? In other words one time I might sort by Index = 0 and another time by Index = 3. The length of all String() in the list is the same. For reference this question is similar to Sort List<String[]> except I am using VB.net and that question is hardwired to Index=0.

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  • Get groups of 4 elements from name value list using LINQ in C#

    - by Kodefoo
    I am wanting to loop through this list of name value pairs and grab them in groups of 4. The data would be like: value1 1 value2 1 value3 1 value4 1 value1 2 value2 2 value3 2 value4 2 and it would group it as 1 list that contains value1 1 value2 1 value3 1 value4 1 and another list that contains value1 2 value2 2 value3 2 value4 2 I know this can be done easily with a for loop, but I am wondering if there is a good way to do it with LINQ.

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  • Change List Settings

    - by Carpentar
    Hello all, I wonder how would I go about doing this. I want to change a behavior for a list. When a list is added into sharepoint site, you can see 'Add New Item' underneath the list. When the user adds a new item, it should be replaced with 'Edit Item' How can I achieve this? Many thanks,

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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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  • Moving an item up and down in a WPF list box

    - by DommyCastles
    I have a list box with a bunch of values in it. I also have an UP button and a DOWN button. With these buttons, I would like to move the selected item in the list box up/down. I am having trouble doing this. Here is my code so far: private void btnDataUp_Click(object sender, RoutedEventArgs e) { int selectedIndex = listBoxDatasetValues.SelectedIndex; //get the selected item in the data list if (selectedIndex != -1 && selectedIndex != 0) //if the selected item is selected and not at the top of the list { //swap items here listBoxDatasetValues.SelectedIndex = selectedIndex - 1; //keep the item selected } } I do not know how to swap the values! Any help would be GREATLY appreciated!

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