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• Is this the proper way to initialize null references in Scala?

  - by Geo

  Let's say I have a MyObject instance which is not initialized: var a:MyObject = null is this the proper way to initialize it to null?

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• Which is preferred: new Nullable<int> or (int?)null ?

  - by abatishchev

  Which way is preferred in expressions like this: int? Id { get { int i; return Int32.TryParse(Request["id"], out i) ? i : (int?)null; } } is it better to cast on null or create a new Nullable<T> ?

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• Make character escape from shot

  - by M28

  Hello all math masters, I got a problem for you: I have a 2D game (top down), and I would like to make the character escape from a shot, but not just walk away from the shot (I mean, don't be pushed by the shot), I want it to have a good dodging skills. The variables are: shotX - shot x position shotY - shot y position shotSpeedX - shot x speed shotSpeedY - shot x speed charX - character x position charY - character y position keyLeft - Set to true to make the character press the to left key keyRight - Set to true to make the character press the to right key keyUp - Set to true to make the character press the to up key keyDown - Set to true to make the character press the down key I can understand the following languages: C/C++ Java Actionscript 2/3 Javascript

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• Drop Down list null value not working for selected text c#?

  - by Tamara JQ

  Hi guys, Basically I have a drop down list which is populated with text and values depending on a selected index of a radio button list. The code is as follows: protected void RBLGender_SelectedIndexChanged(object sender, EventArgs e) { DDLTrous.Items.Clear(); DDLShoes.Items.Clear(); if (RBLGender.SelectedValue.Equals("Male")) { String[] MaleTrouserText = {"[N/A]", "28\"", "30\"", "32\"", "34\"", "36\"", "38\"", "40\"", "42\"", "44\"", "48\""}; String[] MaleTrouserValue = { null, "28\"", "30\"", "32\"", "34\"", "36\"", "38\"", "40\"", "42\"", "44\"", "48\"" }; String[] MaleShoeText = { "[N/A]", "38M", "39M", "40M", "41M", "42M", "43M", "44M", "45M", "46M", "47M" }; String[] MaleShoeValue = { null, "38M", "39M", "40M", "41M", "42M", "43M", "44M", "45M", "46M", "47M" }; for (int i = 0; i < MaleTrouserText.Length; i++) { ListItem MaleList = new ListItem(MaleTrouserText[i], MaleTrouserValue[i]); DDLTrous.Items.Add(MaleList); } for (int i = 0; i < MaleShoeText.Length; i++) { ListItem MaleShoeList = new ListItem(MaleShoeText[i], MaleShoeValue[i]); DDLShoes.Items.Add(MaleShoeList); } } else if (RBLGender.SelectedValue.Equals("Female"))` When the text '[N/A]' is selected I want the value NULL to be inserted into the database. At present when '[N/A]' is selected the value entered into the database is [N/A] does anyone know why? Thanks in advance.

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• Can a WPF ComboBox display alternative text when its selection is null?

  - by Garth T Kidd

  G'day! I want my WPF ComboBox to display some alternative text when its data-bound selection is null. The view model has the expected properties: public ThingoSelectionViewModel : INotifyPropertyChanged { public ThingoSelectionViewModel(IProvideThingos) { this.Thingos = IProvideThingos.GetThingos(); } public ObservableCollection<Thingo> Thingos { get; set; } public Thingo SelectedThingo { get { return this.selectedThingo; } set { // set this.selectedThingo and raise the property change notification } // ... } The view has XAML binding to the view model in the expected way: <ComboBox x:Name="ComboboxDrive" SelectedItem="{Binding Path=SelectedThingo}" IsEditable="false" HorizontalAlignment="Left" MinWidth="100" IsReadOnly="false" Style="{StaticResource ComboboxStyle}" Grid.Column="1" Grid.Row="1" Margin="5" SelectedIndex="0"> <ComboBox.ItemsSource> <CompositeCollection> <ComboBoxItem IsEnabled="False">Select a thingo</ComboBoxItem> <CollectionContainer Collection="{Binding Source={StaticResource Thingos}}" /> </CompositeCollection> </ComboBox.ItemsSource> </ComboBox> The ComboBoxItem wedged into the top is a way to get an extra item at the top. It's pure chrome: the view model stays pure and simple. There's just one problem: the users want "Select a thingo" displayed whenever the ComboBox' selection is null. The users do not want a thingo selected by default. They want to see a message telling them to select a thingo. I'd like to avoid having to pollute the viewmodel with a ThingoWrapper class with a ToString method returning "Select a thingo" if its .ActualThingo property is null, wrapping each Thingo as I populate Thingos, and figuring out some way to prevent the user from selecting the nulled Thingo. Is there a way to display "Select a thingo" within the ComboBox' boundaries using pure XAML, or pure XAML and a few lines of code in the view's code-behind class?

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• Should I make the Cells in a Tiledmap as null when my player hits it

  - by Vishal Kumar

  I am making a Tile Based game using Libgdx. I took the idea from SuperKoalio platformer demo by Mario Zencher. When I wanted to implement Collectables in my game , I simply draw the coins using Tiled Map Editor. When my player hits that, I use to set that cell as null. Someday on this site suggested me not to do so... never use null. I agreed. What can be any other way. If I am using layer.setCell(x,y) to set the cell to any other cell... even if an transparent one .. my player seems to be stopped by an invisible object/hurdle. This is my code: for (Rectangle tile : tiles) { if (koalaRect.overlaps(tile)) { TiledMapTileLayer layer = (TiledMapTileLayer) map.getLayers().get(1); try{ type = layer.getCell((int) tile.x, (int) tile.y).getTile().getProperties().get("tileType").toString(); } catch(Exception e){ System.out.print("Exception in Tiles Property"+e); type="nonbreakable"; } //Let us destroy this cell if(("award".equals(type))){ layer.setCell((int) tile.x, (int) tile.y, null); listener.coin(); score+=100; test = ""+layer.getCell(0, 0).getTile().getProperties().get("tileType"); } //DOING THIS GIVES A BAD EFFECT if(("killer".equals(type))){ //player.health--; //layer.setCell((int) tile.x, (int) tile.y, layer.getCell(20,0)); } // we actually reset the player y-position here // so it is just below/above the tile we collided with // this removes bouncing :) if (player.velocity.y > 0) { player.position.y = (tile.y - Player.height); } Is this a right approach? OR I should create separate Sprite Class called Coin.

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• Matching the superclass's constructor's parameter list, is treating a null default value as a non-null value within a constructor a violation of LSP?

  - by Panzercrisis

  I kind of ran into this when messing around with FlashPunk, and I'm going to use it as an example. Essentially the main sprite class is pretty much class Entity. Entity's constructor has four parameters, each with a default value. One of them is graphic, whose default value is null. Entity is designed to be inherited from, with many such subclasses providing their own graphic within their own internal workings. Normally these subclasses would not have graphic in their constructor's parameter lists, but would simply pick something internally and go with it. However I was looking into possibly still adhering to the Liskov Substitution Principal. Which led me to the following example: package com.blank.graphics { import net.flashpunk.*; import net.flashpunk.graphics.Image; public class SpaceGraphic extends Entity { [Embed(source = "../../../../../../assets/spaces/blank.png")] private const BLANK_SPACE:Class; public function SpaceGraphic(x:Number = 0, y:Number = 0, graphic:Graphic = null, mask:Mask = null) { super(x, y, graphic, mask); if (!graphic) { this.graphic = new Image(BLANK_SPACE); } } } } Alright, so now there's a parameter list in the constructor that perfectly matches the one in the super class's constructor. But if the default value for graphic is used, it'll exhibit two different behaviors, depending on whether you're using the subclass or the superclass. In the superclass, there won't be a graphic, but in the subclass, it'll choose the default graphic. Is this a violation of the Liskov Substitution Principal? Does the fact that subclasses are almost intended to use different parameter lists have any bearing on this? Would minimizing the parameter list violate it in a case like this? Thanks.

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• TSQL Help (SQL Server 2005)

  - by Mick Walker

  I have been playing around with a quite complex SQL Statement for a few days, and have gotten most of it working correctly. I am having trouble with one last part, and was wondering if anyone could shed some light on the issue, as I have no idea why it isnt working: INSERT INTO ExistingClientsAccounts_IMPORT SELECT DISTINCT cca.AccountID, cca.SKBranch, cca.SKAccount, cca.SKName, cca.SKBase, cca.SyncStatus, cca.SKCCY, cca.ClientType, cca.GFCID, cca.GFPID, cca.SyncInput, cca.SyncUpdate, cca.LastUpdatedBy, cca.Deleted, cca.Branch_Account, cca.AccountTypeID FROM ClientsAccounts AS cca INNER JOIN (SELECT DISTINCT ClientAccount, SKAccount, SKDesc, SKBase, SKBranch, ClientType, SKStatus, GFCID, GFPID, Account_Open_Date, Account_Update FROM ClientsAccounts_IMPORT) AS ccai ON cca.Branch_Account = ccai.ClientAccount Table definitions follow: CREATE TABLE [dbo].[ExistingClientsAccounts_IMPORT]( [AccountID] [int] NOT NULL, [SKBranch] [varchar](2) NOT NULL, [SKAccount] [varchar](12) NOT NULL, [SKName] [varchar](255) NULL, [SKBase] [varchar](16) NULL, [SyncStatus] [varchar](50) NULL, [SKCCY] [varchar](5) NULL, [ClientType] [varchar](50) NULL, [GFCID] [varchar](10) NULL, [GFPID] [varchar](10) NULL, [SyncInput] [smalldatetime] NULL, [SyncUpdate] [smalldatetime] NULL, [LastUpdatedBy] [varchar](50) NOT NULL, [Deleted] [tinyint] NOT NULL, [Branch_Account] [varchar](16) NOT NULL, [AccountTypeID] [int] NOT NULL ) ON [PRIMARY] CREATE TABLE [dbo].[ClientsAccounts_IMPORT]( [NEWClientIndex] [bigint] NOT NULL, [ClientGroup] [varchar](255) NOT NULL, [ClientAccount] [varchar](255) NOT NULL, [SKAccount] [varchar](255) NOT NULL, [SKDesc] [varchar](255) NOT NULL, [SKBase] [varchar](10) NULL, [SKBranch] [varchar](2) NOT NULL, [ClientType] [varchar](255) NOT NULL, [SKStatus] [varchar](255) NOT NULL, [GFCID] [varchar](255) NULL, [GFPID] [varchar](255) NULL, [Account_Open_Date] [smalldatetime] NULL, [Account_Update] [smalldatetime] NULL, [SKType] [varchar](255) NOT NULL ) ON [PRIMARY] The error message I get is: Msg 8152, Level 16, State 14, Line 1 String or binary data would be truncated. The statement has been terminated.

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• Join two tables with same # of row but sorted for NULL

  - by VISQL

  I need to join two tables with the same number of rows. Each table has 1 column. There is NO CONNECTING COLUMN to reference for a join. I need to join them side by side because each table was sorted separately so that numeric values are at the top in descinding order. The Table Earners has income values from say 200K down to 0. I cannot just select using 2 cases, because then I will have my first row with Incomes above 100K, but the first 20 or so entries in the second row are NULL. I want the second row to also be sorted descending. I looked up using ORDER BY within CASE but there is no such thing. I have tried to read about row_number() but none of the examples seem to match or make sense. drop table #20plus select case when Income >= 20000 AND Income < 100000 then Income end as 'mula' into #20plus from Earners order by mula desc drop table #100plus select case when Income >= 100000 then Income end as 'dinero' into #100plus from Earners order by dinero desc Select A.dinero, B.mula FROM #100plus as A JOIN #20plus as B ON A.????? = B.????? Since both A and B are sorted descending, moving all NULL to the bottom, what can I reference to join the two tables? Previous output using one SELECT statement with 2 CASE statements dinero mula 2.12688e+007 NULL 1.80031e+007 NULL 1.92415e+006 NULL … … NULL 93530.7 NULL 91000 NULL 84500 Desired output using one SELECT statement after creating two temp TABLES dinero mula 2.12688e+007 93530.7 1.80031e+007 91000 1.92415e+006 84500 … 82500 NULL 82000 NULL … NULL NULL This is Microsoft SQL Server 2008. I'm super new to this, so please give an answer as clear and simplified as possible. Thank you.

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• Behavior of <- NULL on lists versus data.frames for removing data

  - by Ananda Mahto

  Many R users eventually figure out lots of ways to remove elements from their data. One way is to use NULL, particularly when you want to do something like drop a column from a data.frame or drop an element from a list. Eventually, a user comes across a situation where they want to drop several columns from a data.frame at once, and they hit upon <- list(NULL) as the solution (since using <- NULL will result in an error). A data.frame is a special type of list, so it wouldn't be too tough to imagine that the approaches for removing items from a list should be the same as removing columns from a data.frame. However, they produce different results, as can be seen in the example below. ## Make some small data--two data.frames and two lists cars1 <- cars2 <- head(mtcars)[1:4] cars3 <- cars4 <- as.list(cars2) ## Demonstration that the `list(NULL)` approach works cars1[c("mpg", "cyl")] <- list(NULL) cars1 # disp hp # Mazda RX4 160 110 # Mazda RX4 Wag 160 110 # Datsun 710 108 93 # Hornet 4 Drive 258 110 # Hornet Sportabout 360 175 # Valiant 225 105 ## Demonstration that simply using `NULL` does not work cars2[c("mpg", "cyl")] <- NULL # Error in `[<-.data.frame`(`*tmp*`, c("mpg", "cyl"), value = NULL) : # replacement has 0 items, need 12 Switch to applying the same concept to a list, and compare the difference in behavior. ## Does not fully drop the items, but sets them to `NULL` cars3[c("mpg", "cyl")] <- list(NULL) # $mpg # NULL # # $cyl # NULL # # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 ## *Does* drop the `list` items while this would ## have produced an error with a `data.frame` cars4[c("mpg", "cyl")] <- NULL # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 The main questions I have are, if a data.frame is a list, why does it behave so differently in this scenario? Is there a foolproof way of knowing when an element will be dropped, when it will produce an error, and when it will simply be given a NULL value? Or do we depend on trial-and-error for this?

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• Are null references really a bad thing?

  - by Tim Goodman

  I've heard it said that the inclusion of null references in programming languages is the "billion dollar mistake". But why? Sure, they can cause NullReferenceExceptions, but so what? Any element of the language can be a source of errors if used improperly. And what's the alternative? I suppose instead of saying this: Customer c = Customer.GetByLastName("Goodman"); // returns null if not found if (c != null) { Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } You could say this: if (Customer.ExistsWithLastName("Goodman")) { Customer c = Customer.GetByLastName("Goodman") // throws error if not found Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } But how is that better? Either way, if you forget to check that the customer exists, you get an exception. I suppose that a CustomerNotFoundException is a bit easier to debug than a NullReferenceException by virtue of being more descriptive. Is that all there is to it?

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• Would it be possible to have a UTF-8-like encoding limited to 3 bytes per character?

  - by dan04

  UTF-8 requires 4 bytes to represent characters outside the BMP. That's not bad; it's no worse than UTF-16 or UTF-32. But it's not optimal (in terms of storage space). There are 13 bytes (C0-C1 and F5-FF) that are never used. And multi-byte sequences that are not used such as the ones corresponding to "overlong" encodings. If these had been available to encode characters, then more of them could have been represented by 2-byte or 3-byte sequences (of course, at the expense of making the implementation more complex). Would it be possible to represent all 1,114,112 Unicode code points by a UTF-8-like encoding with at most 3 bytes per character? If not, what is the maximum number of characters such an encoding could represent? By "UTF-8-like", I mean, at minimum: The bytes 0x00-0x7F are reserved for ASCII characters. Byte-oriented find / index functions work correctly. You can't find a false positive by starting in the middle of a character like you can in Shift-JIS.

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• Character Set Issues when Upgrading from Symfony 2.0.* to Symfony 2.1.*?

  - by Adam Stacey

  I have recently upgraded my staging test site to the latest version of Symfony and updated all the vendors using composer as instructed in the upgrade document that comes with the download. Everything has all updated fine, but I have noticed now that some bits of HTML are not displaying in the Twig templates. I did a comparison with the current live site and it appears to be a character set issue. As an example I had a drop down list that had the following value in: Kitchen Ducting > Ducting Kits > Ducting Kit 4” / 100mm In the updated site the drop-down list item just appeared blank. When I used Twig's raw function it then displayed the item again, but with the dreaded question mark in a black diamond. Kitchen Ducting > Ducting Kits > Ducting Kit 4? / 100mm Things that you should know that may help: The staging test site and live site are both on the same server. In my httpd.conf file I have 'AddDefaultCharset utf-8'. In my php.ini file I have 'default_charset = "utf-8"'. The HTML file served has the Content-Type meta tag 'content="text/html; charset=utf-8"' My database is InnoDB and uses 'utf8' as the default character set and 'utf8_general_ci' as default collation. All tables in the database also use the defaults. I looked into BOM with UTF8, but could not work out if that was a problem or not?

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• Why is my program printing out the null termination character?

  - by Tyler Pfaff

  When I run this, it will SOMETIMES print out a null termination character. Most of the time it will, and probably 1/5 times it will print just the characters. void cryptogram::Encrypt(){ cout<<"encrypt"<tempS){ len=tempS.length(); int a=0; for(int j=0;j if(j!=len){ //if the word still has more characters j++; a=0; }else{ //if the word is done being scanned cout<<" "; } } } } } } } So that's it and this is the corresponding EXPECTED output that is printed SOMETIMES xvk bkikhxlr wggbtfkj wiylekgbdhx wjjm hko wigbtubxt xvk iwhj uedjkm glctb gvrmdiwhj iebbdielmeggtbx ctb xvtmk gbtubxvk wjjdxdthgbtubodll khvxvk imkbfdik xt xvk bkudth whj gbtfdjk hko tgxdthm whj tggtbxehdxdkm ctb mxejkhxmibdzdhtltur whj pemxdik mxejdkm mxdh cok wbk wlmt gbkgctb cteb hko zdh cgvrmdikjeiwhj qdhkmdtlturzzkjdydtivkzdmxbrw zdh zdjjlkkjeiwhj w jtixtbdh kjeiwjzdhdmxbittgkbodxv mjme whj eimj This is what normally prints though xvkÈ bkikhxlrÈ wggbtfkjÈ wiylekgbdhxÈ wjjmÈ hkoÈ wigbtubxtÈ xvkÈ iwhjÈ uedjkmÈ glctbÈ gvrmdiwhjÈ iebbdielmeggtbxÈ ctbÈ xvtmkÈ gbtubxvkÈ wjjdxdthgbtubodllÈ khvxvkÈ imkbfdikÈ xtÈ xvkÈ bkudthÈ whjÈ gbtfdjkÈ hkoÈ tgxdthmÈ whjÈ tggtbxehdxdkmÈ ctbÈ mxejkhxmibdzdhtlturÈ whjÈ pemxdikÈ mxejdkmÈ mxdhÈ cokÈ wbkÈ wlmtÈ gbkgctbÈ ctebÈ hkoÈ zdhÈ cgvrmdikjeiwhjÈ qdhkmdtlturzzkjdydtivkzdmxbrwÈ zdhÈ zdjjlkkjeiwhjÈ wÈ jtixtbdhÈ kjeiwjzdhdmxbittgkbodxvÈ mjmeÈ whjÈ eimj or some variation of an odd character at the end of each word This is what the cryptogram array is filled with by the way wyijkcuvdpqlzhtgabmxefonrs

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• Exporting 3DS Max animated biped character into Assimp

  - by Doug Kavendek

  I've been having some trouble with MD5 meshes exported from 3DS Max into my C++ program, using Assimp to import the model and its skeletal animation. If the models were rigged manually with bones, the export and animations work perfectly, but if they were rigged as a biped character, the animation hits a "deadly import error" and all the bones appear to get smooshed together into a big pile. This seems like it might just be a limitation of the MD5 exporter (we're currently using the one found here. Our plan is to try out a different MD5 exporter (this one), and if that still has problems, then try switching from MD5 to COLLADA. Our modeler won't be able to make time to try out these other exporters for a few days, so in the meantime I wanted to see if there were any better methods out there for getting biped rigged models from 3DS Max into our app via Assimp. Out of Assimp's supported formats, I need to figure out which will support the following: Skeletal animations Exportable from 3DS Max biped rigged models Failing that, an alternative would be a way to convert a biped character to its corresponding bones before exporting. We did find one script to do that, but it only seems meant as a starting point for modeling -- it doesn't carry over any hierarchy, skinning, or animation -- so it can't be used solely during export.

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• Queueing up character actions

  - by TheBroodian

  I'm developing a 2D platformer with action-fighter elements. Currently things are working relatively smoothly but I'm having difficulty sorting something out. For the time, keeping my character's states and actions separated and preventing them from stepping on each others' toes is working out well and properly, but I would like to add a feature to my character to get him to behave a little bit more fluidly for the player. At the moment, he has numerous attacks and abilities that he can execute, all of them being executed with button presses. Here lies the problem: Being as everything is executed through button presses, while an action is in progress I flag the game to disregard further button presses until the action has completed. Therefore, consecutive actions cannot be performed until after the previous action has completed entirely. In runtime this behavior feels very icky, and very ungamelike. In games that rest most memorably at the forefront of my mind the player is able to execute button commands during the process of actions, and at the end of the current action, the following action is executed (seems like some sort of a queue system or something) Can anybody offer any guidance with this?

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• Facing a character towards the mouse

  - by ratata

  I'm trying to port a simple 2d top down shooter game from C++(Allegro) to Java and i'm having problems with rotating my character. Here's the code i used in c++ if (keys[A]) RotateRight(player, degree); if (keys[D]) RotateLeft(player, degree); void RotateLeft(Player& player, float& degree) { degree += player.rotatingSpeed; if ( degree >= 360 ) degree = 0; } void RotateRight(Player& player, float& degree) { degree -= player.rotatingSpeed; if ( degree <= 0) degree = 360; } And this is what i have in render section: al_draw_rotated_bitmap(player.image, player.frameWidth / 2, player.frameHeight / 2, player.x, player.y, degree * 3.14159 / 180, 0); Instead of using A-D keys i want to use mouse this time. I've been searching since last night and came up to few sample codes however noone of them worked. For example this just made my character to circle around the map: int centerX = width / 2; int centerY = height / 2; double angle = Math.atan2(centerY - mouseY, centerX - mouseX) - Math.PI / 2; ((Graphics2D)g).rotate(angle, centerX, centerY); g.fillRect(...); // draw your rectangle Any help is much appreciated.

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• Issue with TagBuilder.MergeAttribute for parameter null

  - by The Yur

  I would like to use Razor's feature not to produce attribute output inside a tag in case when attribute's value is null. So when Razor meets <div class="@var" where @var is null, the output will be mere <div. I've created some Html extension method to write text inside tag. The method takes header text, level (h1..h6), and html attributes as simple object. The code is: public static MvcHtmlString WriteHeader(this HtmlHelper html, string s, int? hLevel = 1, object htmlAttributes = null) { if ((hLevel == null) || (hLevel < 1 || hLevel > 4) || (s.IsNullOrWhiteSpace())) return new MvcHtmlString(""); string cssClass = null, cssId = null, cssStyle = null; if (htmlAttributes != null) { var T = htmlAttributes.GetType(); var propInfo = T.GetProperty("class"); var o = propInfo.GetValue(htmlAttributes); cssClass = o.ToString().IsNullOrWhiteSpace() ? null : o.ToString(); propInfo = T.GetProperty("id"); o = propInfo.GetValue(htmlAttributes); cssId = o.ToString().IsNullOrWhiteSpace() ? null : o.ToString(); propInfo = T.GetProperty("style"); o = propInfo.GetValue(htmlAttributes); cssStyle = o.ToString().IsNullOrWhiteSpace() ? null : o.ToString(); } var hTag = new TagBuilder("h" + hLevel); hTag.MergeAttribute("id", cssId); hTag.MergeAttribute("class", cssClass); hTag.MergeAttribute("style", cssStyle); hTag.InnerHtml = s; return new MvcHtmlString(hTag.ToString()); } I found that in spite of null values for "class" and "style" attributes TagBuilder still puts them as empty strings, like <h1 class="" style="" But for id attribute it surprisingly works, so when id's value is null, there is no id attribute in tag. My question - is such behavior something that should actually happen? How can I achieve absent attributes with null values using TagBuilder? I tried this in VS2013, MVC 5.

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• SQL Server Date Comparison Functions

  - by HighAltitudeCoder

  A few months ago, I found myself working with a repetitive cursor that looped until the data had been manipulated enough times that it was finally correct.  The cursor was heavily dependent upon dates, every time requiring the earlier of two (or several) dates in one stored procedure, while requiring the later of two dates in another stored procedure. In short what I needed was a function that would allow me to perform the following evaluation: WHERE MAX(Date1, Date2) < @SomeDate The problem is, the MAX() function in SQL Server does not perform this functionality.  So, I set out to put these functions together.  They are titled: EarlierOf() and LaterOf(). /**********************************************************                               EarlierOf.sql   **********************************************************/ /**********************************************************   Return the later of two DATETIME variables.   Parameter 1: DATETIME1 Parameter 2: DATETIME2   Works for a variety of DATETIME or NULL values. Even though comparisons with NULL are actually indeterminate, we know conceptually that NULL is not earlier or later than any other date provided.   SYNTAX: SELECT dbo.EarlierOf('1/1/2000','12/1/2009') SELECT dbo.EarlierOf('2009-12-01 00:00:00.000','2009-12-01 00:00:00.521') SELECT dbo.EarlierOf('11/15/2000',NULL) SELECT dbo.EarlierOf(NULL,'1/15/2004') SELECT dbo.EarlierOf(NULL,NULL)   **********************************************************/ USE AdventureWorks GO   IF EXISTS       (SELECT *       FROM sysobjects       WHERE name = 'EarlierOf'       AND xtype = 'FN'       ) BEGIN             DROP FUNCTION EarlierOf END GO   CREATE FUNCTION EarlierOf (       @Date1                              DATETIME,       @Date2                              DATETIME )   RETURNS DATETIME   AS BEGIN       DECLARE @ReturnDate     DATETIME         IF (@Date1 IS NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = NULL             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NULL AND @Date2 IS NOT NULL)       BEGIN             SET @ReturnDate = @Date2             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NOT NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = @Date1             GOTO EndOfFunction       END         ELSE       BEGIN             SET @ReturnDate = @Date1             IF @Date2 < @Date1                   SET @ReturnDate = @Date2             GOTO EndOfFunction       END         EndOfFunction:       RETURN @ReturnDate   END -- End Function GO   ---- Set Permissions --GRANT SELECT ON EarlierOf TO UserRole1 --GRANT SELECT ON EarlierOf TO UserRole2 --GO                                                                                             The inverse of this function is only slightly different. /**********************************************************                               LaterOf.sql   **********************************************************/ /**********************************************************   Return the later of two DATETIME variables.   Parameter 1: DATETIME1 Parameter 2: DATETIME2   Works for a variety of DATETIME or NULL values. Even though comparisons with NULL are actually indeterminate, we know conceptually that NULL is not earlier or later than any other date provided.   SYNTAX: SELECT dbo.LaterOf('1/1/2000','12/1/2009') SELECT dbo.LaterOf('2009-12-01 00:00:00.000','2009-12-01 00:00:00.521') SELECT dbo.LaterOf('11/15/2000',NULL) SELECT dbo.LaterOf(NULL,'1/15/2004') SELECT dbo.LaterOf(NULL,NULL)   **********************************************************/ USE AdventureWorks GO   IF EXISTS       (SELECT *       FROM sysobjects       WHERE name = 'LaterOf'       AND xtype = 'FN'       ) BEGIN             DROP FUNCTION LaterOf END GO   CREATE FUNCTION LaterOf (       @Date1                              DATETIME,       @Date2                              DATETIME )   RETURNS DATETIME   AS BEGIN       DECLARE @ReturnDate     DATETIME         IF (@Date1 IS NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = NULL             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NULL AND @Date2 IS NOT NULL)       BEGIN             SET @ReturnDate = @Date2             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NOT NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = @Date1             GOTO EndOfFunction       END         ELSE       BEGIN             SET @ReturnDate = @Date1             IF @Date2 > @Date1                   SET @ReturnDate = @Date2             GOTO EndOfFunction       END         EndOfFunction:       RETURN @ReturnDate   END -- End Function GO   ---- Set Permissions --GRANT SELECT ON LaterOf TO UserRole1 --GRANT SELECT ON LaterOf TO UserRole2 --GO                                                                                             The interesting thing about this function is its simplicity and the built-in NULL handling functionality.  Its interesting, because it seems like something should already exist in SQL Server that does this.  From a different vantage point, if you create this functionality and it is easy to use (ideally, intuitively self-explanatory), you have made a successful contribution. Interesting is good.  Self-explanatory, or intuitive is FAR better.  Happy coding! Graeme

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• Arraylist is null; I cannot access books in the arraylist

  - by user3701380

  I am a beginner-intermediate java programmer and I am getting a null pointer exception from my arraylist. I am writing a bookstore program for APCS and when i add the book, it is supposed to add to the arraylist in the inventory class. But when i call a method to search for a book (e.g. by title), it shows that there isn't anything in the arraylist. //Here is my inventory class -- it has all methods for adding the book or searching for one The searching methods are in getBookByTitle, getBookByAuthor, and getBookByISBN and the method for adding a book is addBook package webbazonab; //Inventory Class //Bharath Senthil //Ansh Sikka import java.util.ArrayList; public class Inventory{ private ArrayList<Book> allBooks = new ArrayList<Book>(); private String bookTitles; private String bookAuthors; private String bookPrices; private String bookCopies; private String ISBNs; public Inventory() { } //@param double price, int copies, String bookTitle, String Author, String isbnNumber public void addBooks(Book addedBook){ allBooks.add(addedBook); } public boolean isAvailable(){ for(Book myBook : allBooks){ if(myBook.copiesLeft() == 0) return false; } return true; } public String populateTitle(){ for (Book titleBooks : allBooks){ bookTitles = titleBooks.getTitle() + "\n"; return bookTitles; } return bookTitles; } public String populateAuthor(){ for(Book authorBooks : allBooks){ bookAuthors = authorBooks.getAuthor() + "\n"; return bookAuthors; } return bookAuthors; } public String populatePrice(){ for (Book pricedBooks : allBooks){ bookPrices = String.valueOf(pricedBooks.getPrice()) + "\n"; } return "$" + bookPrices; } /** * * @return */ public String populateCopies(){ for (Book amtBooks : allBooks){ bookCopies = String.valueOf(amtBooks.copiesLeft()) + "\n"; return bookCopies; } return bookCopies; } public String populateISBN(){ for (Book isbnNums : allBooks){ ISBNs = isbnNums.getIsbn() + "\n"; return ISBNs; } return ISBNs; } @SuppressWarnings("empty-statement") public Book getBookByTitle(String titleSearch) { for(Book titleBook : allBooks) { if (titleBook.getTitle().equals(titleSearch)) { return titleBook; } } return null; } public Book getBookByISBN(String isbnSearch){ for(Book isbnBookSearches : allBooks){ if(isbnBookSearches.getIsbn().equals(isbnSearch)){ return isbnBookSearches; } } return null; } public Book getBookByAuthor(String authorSearch){ for(Book authorBookSearches : allBooks){ if(authorBookSearches.getAuthor().equals(authorSearch)){ return authorBookSearches; } } return null; } public void sort(){ for(int i = 0; i < allBooks.size(); i++) { for(int k = 0; k < allBooks.size(); k++) { if(((Book) allBooks.get(i)).getIsbn().compareTo(((Book) allBooks.get(k)).getIsbn()) < 1) { Book temp = (Book) allBooks.get(k); allBooks.set(k, allBooks.get(i)); allBooks.set(i, temp); } else if(((Book) allBooks.get(i)).getIsbn().compareTo(((Book) allBooks.get(k)).getIsbn()) > 1) { Book temp = (Book) allBooks.get(i); allBooks.set(i, allBooks.get(k)); allBooks.set(k, temp); } } } } public ArrayList<Book> getBooks(){ return allBooks; } } //The exception occurs when i call the method here (in another class): Inventory lib = new Inventory(); jTextField12.setText(lib.getBookByAuthor(authorSearch).getTitle()); Here is my book class if you need it package webbazonab; //Webbazon AB //Project By: Ansh Sikka and Bharath Senthil public class Book { private double myPrice; private String myTitle; private String bookAuthor; private String isbn; private int myCopies; public Book(double price, int copies, String bookTitle, String Author, String isbnNumber) { myPrice = price; myCopies = copies; myTitle = bookTitle; bookAuthor = Author; isbn = isbnNumber; } public double getPrice() { return myPrice; } public String getIsbn() { return isbn; } public String getTitle() { return myTitle; } public String getAuthor() { return bookAuthor; } public int copiesLeft(){ return myCopies; } public String notFound(){ return "The book you searched for could not be found!"; } public String toString() { return "Title: " + getTitle() + "\nAuthor: " + getAuthor() + "\nNumber of Available Books: " + copiesLeft() + "\nPrice: $" + getPrice(); } } Thanks!

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• How to insert null value for numeric field of a datatable in c#?

  - by Pandiya Chendur

  Consider My dynamically generated datatable contains the following fileds Id,Name,Mob1,Mob2 If my datatable has this it get inserted successfully, Id Name Mob1 Mob2 1 acp 9994564564 9568848526 But when it is like this it gets failed saying, Id Name Mob1 Mob2 1 acp 9994564564 The given value of type String from the data source cannot be converted to type decimal of the specified target column. I generating my datatable by readingt a csv file, CSVReader reader = new CSVReader(CSVFile.PostedFile.InputStream); string[] headers = reader.GetCSVLine(); DataTable dt = new DataTable(); foreach (string strHeader in headers) { dt.Columns.Add(strHeader); } string[] data; while ((data = reader.GetCSVLine()) != null) { dt.Rows.Add(data); } Any suggestion how to insert null value for numeric field during BulkCopy in c#... EDIT: I tried this dt.Columns["Mob2"].AllowDBNull = true; but it doesn't seem to work...

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• MS Access: How to replace blank (null ) values with 0 for all records?

  - by rick

  MS Access: How to replace blank (null ) values with 0 for all records? I guess it has to be done using SQL. I can use Find and Replace to replace 0 with blank, but not the other way around (won't "find" a blank, even if I enter [Ctrl-Spacebar] which inserts a space. So I guess I need to do SQL where I find null values for MyField, then replace all of them with 0. Any help is greatly appreciated. Thanks, The Find & Replace guy.

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• Problems in Binary Search Tree

  - by user2782324

  This is my first ever trial at implementing the BST, and I am unable to get it done. Please help The problem is that When I delete the node if the node is in the right subtree from the root or if its a right child in the left subtree, then it works fine. But if the node is in the left subtree from root and its any left child, then it does not get deleted. Can someone show me what mistake am I doing?? the markedNode here gets allocated to the parent node of the node to be deleted. the minValueNode here gets allocated to a node whose left value child is the smallest value and it will be used to replace the value to be deleted. package DataStructures; class Node { int value; Node rightNode; Node leftNode; } class BST { Node rootOfTree = null; public void insertintoBST(int value) { Node markedNode = rootOfTree; if (rootOfTree == null) { Node newNode = new Node(); newNode.value = value; rootOfTree = newNode; newNode.rightNode = null; newNode.leftNode = null; } else { while (true) { if (value >= markedNode.value) { if (markedNode.rightNode != null) { markedNode = markedNode.rightNode; } else { Node newNode = new Node(); newNode.value = value; markedNode.rightNode = newNode; newNode.rightNode = null; newNode.leftNode = null; break; } } if (value < markedNode.value) { if (markedNode.leftNode != null) { markedNode = markedNode.leftNode; } else { Node newNode = new Node(); newNode.value = value; markedNode.leftNode = newNode; newNode.rightNode = null; newNode.leftNode = null; break; } } } } } public void searchBST(int value) { Node markedNode = rootOfTree; if (rootOfTree == null) { System.out.println("Element Not Found"); } else { while (true) { if (value > markedNode.value) { if (markedNode.rightNode != null) { markedNode = markedNode.rightNode; } else { System.out.println("Element Not Found"); break; } } if (value < markedNode.value) { if (markedNode.leftNode != null) { markedNode = markedNode.leftNode; } else { System.out.println("Element Not Found"); break; } } if (value == markedNode.value) { System.out.println("Element Found"); break; } } } } public void deleteFromBST(int value) { Node markedNode = rootOfTree; Node minValueNode = null; if (rootOfTree == null) { System.out.println("Element Not Found"); return; } if (rootOfTree.value == value) { if (rootOfTree.leftNode == null && rootOfTree.rightNode == null) { rootOfTree = null; return; } else if (rootOfTree.leftNode == null ^ rootOfTree.rightNode == null) { if (rootOfTree.rightNode != null) { rootOfTree = rootOfTree.rightNode; return; } else { rootOfTree = rootOfTree.leftNode; return; } } else { minValueNode = rootOfTree.rightNode; if (minValueNode.leftNode == null) { rootOfTree.rightNode.leftNode = rootOfTree.leftNode; rootOfTree = rootOfTree.rightNode; } else { while (true) { if (minValueNode.leftNode.leftNode != null) { minValueNode = minValueNode.leftNode; } else { break; } } // Minvalue to the left of minvalue node rootOfTree.value = minValueNode.leftNode.value; // The value has been swapped if (minValueNode.leftNode.leftNode == null && minValueNode.leftNode.rightNode == null) { minValueNode.leftNode = null; } else { if (minValueNode.leftNode.leftNode != null) { minValueNode.leftNode = minValueNode.leftNode.leftNode; } else { minValueNode.leftNode = minValueNode.leftNode.rightNode; } // Minvalue deleted } } } } else { while (true) { if (value > markedNode.value) { if (markedNode.rightNode != null) { if (markedNode.rightNode.value == value) { break; } else { markedNode = markedNode.rightNode; } } else { System.out.println("Element Not Found"); return; } } if (value < markedNode.value) { if (markedNode.leftNode != null) { if (markedNode.leftNode.value == value) { break; } else { markedNode = markedNode.leftNode; } } else { System.out.println("Element Not Found"); return; } } } // Parent of the required element found // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// if (markedNode.rightNode != null) { if (markedNode.rightNode.value == value) { if (markedNode.rightNode.rightNode == null && markedNode.rightNode.leftNode == null) { markedNode.rightNode = null; return; } else if (markedNode.rightNode.rightNode == null ^ markedNode.rightNode.leftNode == null) { if (markedNode.rightNode.rightNode != null) { markedNode.rightNode = markedNode.rightNode.rightNode; return; } else { markedNode.rightNode = markedNode.rightNode.leftNode; return; } } else { if (markedNode.rightNode.value == value) { minValueNode = markedNode.rightNode.rightNode; } else { minValueNode = markedNode.leftNode.rightNode; } if (minValueNode.leftNode == null) { // MinNode has no left value markedNode.rightNode = minValueNode; return; } else { while (true) { if (minValueNode.leftNode.leftNode != null) { minValueNode = minValueNode.leftNode; } else { break; } } // Minvalue to the left of minvalue node if (markedNode.leftNode != null) { if (markedNode.leftNode.value == value) { markedNode.leftNode.value = minValueNode.leftNode.value; } } if (markedNode.rightNode != null) { if (markedNode.rightNode.value == value) { markedNode.rightNode.value = minValueNode.leftNode.value; } } // MarkedNode exchanged if (minValueNode.leftNode.leftNode == null && minValueNode.leftNode.rightNode == null) { minValueNode.leftNode = null; } else { if (minValueNode.leftNode.leftNode != null) { minValueNode.leftNode = minValueNode.leftNode.leftNode; } else { minValueNode.leftNode = minValueNode.leftNode.rightNode; } // Minvalue deleted } } } // //////////////////////////////////////////////////////////////////////////////////////////////////////////////// if (markedNode.leftNode != null) { if (markedNode.leftNode.value == value) { if (markedNode.leftNode.rightNode == null && markedNode.leftNode.leftNode == null) { markedNode.leftNode = null; return; } else if (markedNode.leftNode.rightNode == null ^ markedNode.leftNode.leftNode == null) { if (markedNode.leftNode.rightNode != null) { markedNode.leftNode = markedNode.leftNode.rightNode; return; } else { markedNode.leftNode = markedNode.leftNode.leftNode; return; } } else { if (markedNode.rightNode.value == value) { minValueNode = markedNode.rightNode.rightNode; } else { minValueNode = markedNode.leftNode.rightNode; } if (minValueNode.leftNode == null) { // MinNode has no left value markedNode.leftNode = minValueNode; return; } else { while (true) { if (minValueNode.leftNode.leftNode != null) { minValueNode = minValueNode.leftNode; } else { break; } } // Minvalue to the left of minvalue node if (markedNode.leftNode != null) { if (markedNode.leftNode.value == value) { markedNode.leftNode.value = minValueNode.leftNode.value; } } if (markedNode.rightNode != null) { if (markedNode.rightNode.value == value) { markedNode.rightNode.value = minValueNode.leftNode.value; } } // MarkedNode exchanged if (minValueNode.leftNode.leftNode == null && minValueNode.leftNode.rightNode == null) { minValueNode.leftNode = null; } else { if (minValueNode.leftNode.leftNode != null) { minValueNode.leftNode = minValueNode.leftNode.leftNode; } else { minValueNode.leftNode = minValueNode.leftNode.rightNode; } // Minvalue deleted } } } } // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// } } } } } } public class BSTImplementation { public static void main(String[] args) { BST newBst = new BST(); newBst.insertintoBST(19); newBst.insertintoBST(13); newBst.insertintoBST(10); newBst.insertintoBST(20); newBst.insertintoBST(5); newBst.insertintoBST(23); newBst.insertintoBST(28); newBst.insertintoBST(16); newBst.insertintoBST(27); newBst.insertintoBST(9); newBst.insertintoBST(4); newBst.insertintoBST(22); newBst.insertintoBST(17); newBst.insertintoBST(30); newBst.insertintoBST(40); newBst.deleteFromBST(5); newBst.deleteFromBST(4); newBst.deleteFromBST(9); newBst.deleteFromBST(10); newBst.deleteFromBST(13); newBst.deleteFromBST(16); newBst.deleteFromBST(17); newBst.searchBST(5); newBst.searchBST(4); newBst.searchBST(9); newBst.searchBST(10); newBst.searchBST(13); newBst.searchBST(16); newBst.searchBST(17); System.out.println(); newBst.deleteFromBST(20); newBst.deleteFromBST(23); newBst.deleteFromBST(27); newBst.deleteFromBST(28); newBst.deleteFromBST(30); newBst.deleteFromBST(40); newBst.searchBST(20); newBst.searchBST(23); newBst.searchBST(27); newBst.searchBST(28); newBst.searchBST(30); newBst.searchBST(40); } }

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• C++ How do you set an array of pointers to null in an initialiser list like way?

  - by boredjoe

  I am aware you cannot use an initialiser list for an array. However I have heard of ways that you can set an array of pointers to NULL in a way that is similar to an initialiser list. I am not certain how this is done. I have heard that a pointer is set to NULL by default, though I do not know if this is guaranteed/ in the C++ standard. I am also not sure if initialising through the new operator compared to normal allocation can make a difference too.

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• Table Name is null in the sqlite database in android device

  - by Mahe

  I am building a simple app which stores some contacts and retrieves contacts in android phone device. I have created my own database and a table and inserting the values to the table in phone. My phone is not rooted. So I cannot access the files, but I see that values are stored in the table. And tested on a emulator also. Till here it is fine. Display all the contacts in a list by fetching data from table. This is also fine. But the problem is When I am trying to delete the record, it shows the table name is null in the logcat(not an exception), and the data is not deleted. But in emulator the data is getting deleted from table. I am not able to achieve this through phone. This is my code for deleting, public boolean onContextItemSelected(MenuItem item) { super.onContextItemSelected(item); AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item .getMenuInfo(); int menuItemIndex = item.getItemId(); String[] menuItems = getResources().getStringArray(R.array.menu); String menuItemName = menuItems[menuItemIndex]; String listItemName = Customers[info.position]; if (item.getTitle().toString().equalsIgnoreCase("Delete")) { Toast.makeText( context, "Selected List item is: " + listItemName + "MenuItem is: " + menuItemName, Toast.LENGTH_LONG).show(); DB = context.openOrCreateDatabase("CustomerDetails.db", MODE_PRIVATE, null); try { int pos = info.position; pos = pos + 1; Log.d("", "customers[pos]: " + Customers[info.position]); Cursor c = DB .rawQuery( "Select customer_id,first_name,last_name from CustomerInfo", null); int rowCount = c.getCount(); DB.delete(Table_name, "customer_id" + "=" + String.valueOf(pos), null); DB.close(); Log.d("", "" + String.valueOf(pos)); Toast.makeText(context, "Deleted Customer", Toast.LENGTH_LONG) .show(); // Customers[info.position]=null; getCustomers(); } catch (Exception e) { Toast.makeText(context, "Delete unsuccessfull", Toast.LENGTH_LONG).show(); } } this is my logcat, 07-02 10:12:42.976: D/Cursor(1560): Database path: CustomerDetails.db 07-02 10:12:42.976: D/Cursor(1560): Table name : null 07-02 10:12:42.984: D/Cursor(1560): Database path: CustomerDetails.db 07-02 10:12:42.984: D/Cursor(1560): Table name : null Don't know the reason why data is not being deleted. Data exists in the table. This is the specification I have given for creating the table public static String customer_id="customer_id"; public static String site_id="site_id"; public static String last_name="last_name"; public static String first_name="first_name"; public static String phone_number="phone_number"; public static String address="address"; public static String city="city"; public static String state="state"; public static String zip="zip"; public static String email_address="email_address"; public static String custlat="custlat"; public static String custlng="custlng"; public static String Table_name="CustomerInfo"; final SQLiteDatabase DB = context.openOrCreateDatabase( "CustomerDetails.db", MODE_PRIVATE, null); final String CREATE_TABLE = "create table if not exists " + Table_name + " (" + customer_id + " integer primary key autoincrement, " + first_name + " text not null, " + last_name + " text not null, " + phone_number+ " integer not null, " + address+ " text not null, " + city+ " text not null, " + state+ " text not null, " + zip+ " integer not null, " + email_address+ " text not null, " + custlat+ " double, " + custlng+ " double " +" );"; DB.execSQL(CREATE_TABLE); DB.close(); Please correct my code. I am struggling from two days. Any help is appreciated!!

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