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Could someone help me debug my app (not very big)?

- by Alex

Not sure if this kind of help is accepted to ask for here, tell me if it isn't. It has to get done before tomorrow, it's not entirerly finished but it should work somewhat ok by now. I'm trying to use the Eclipse debugger (not very used to it). I have my top-level or main class, which is Game, in which I have a constructor and a main method. In the main method I create a new "Game", initiating the constructor. public static void main(String[] args){ Game chess = new Game(); } public Game(){ Board board = new Board(); That's the first thing the debugger reacts to: Thread [main] (Suspended) ClassNotFoundException(Object).<init>() line: 20 [local variables unavailable] ClassNotFoundException(Throwable).<init>(String, Throwable) line: 217 ClassNotFoundException(Exception).<init>(String, Throwable) line: not available ClassNotFoundException.<init>(String) line: not available URLClassLoader$1.run() line: not available AccessController.doPrivileged(PrivilegedExceptionAction<T>, AccessControlContext) line: not available [native method] Launcher$ExtClassLoader(URLClassLoader).findClass(String) line: not available Launcher$ExtClassLoader.findClass(String) line: not available Launcher$ExtClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader.loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String) line: not available Game.<init>() line: 15 Game.main(String[]) line: 11 Line 11 is the one line in my main method, line 15 is the instantiation of "board".

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PHP Multi-Domain Sessions; ini_set Not Working?

- by SumWon

Hello, I'm trying to set it up so if you log in to my website the session carries over to all sub-domains of my website. For example, if you go to domain.com and log in, then go to sub.domain.com, you'll already be logged in at sub.domain.com. To my understanding, you would want to use ini_set('session.cookie_domain','.domain.com') and then session_start(), then set your session variables, but this isn't working. Example of what I'm doing: Code for domain.com: <?php ini_set('session.cookie_domain','.domain.com'); session_start(); $_SESSION['variable'] = 1; ?> Code for sub.domain.com: <?php session_start(); echo $_SESSION['variable']; ?> But $_SESSION['variable'] isn't set. I've also tried using ini_set() in the sub.domain.com code, but it made no difference. I've verified that setting session.cookie_domain is working by using ini_get(). What am I doing wrong? Thanks!

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Hiding Url for asp.net page

- by user204588

Hello, I'm creating an html page that is posted to another page for processing. I don't want users to see the weird URL they are redirected to and I was using FRAMES but I can't figure out how to add my HTML page dynamically because I need the variables and either add frames or try another way to accomplish this. So, based on how I'm creating the page below, how can I hide the URL and add something that I want. Here is how I'm creating the page. StringBuilder sb = new StringBuilder(); sb.Append("<html><head></head>"); sb.Append("<body onload=\"document.frmLaunch.submit();\">"); sb.Append("<form name=\"frmLaunch\" action=\"" + variableTargetURL + "\" method=\"post\">"); sb.Append("<input type=hidden name=\"testVariable\" value=\"" + variableTest + "\">"); sb.Append("</form>"); sb.Append("</body></html>"); HttpResponse response = HttpContext.Current.Response; response.Clear(); response.Write(sb.ToString()); response.End();

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Need help getting buttons to work...

- by Mike Droid

I am trying to get my first button to update a display number in my view when clicked. This view will have several buttons and "outputs" displayed. After reading examples and Q's here, I finally put something together that runs, but my first button is still not working; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.ship_layout); mSwitcher = (TextSwitcher) findViewById(R.id.eng_val); } private TextSwitcher mSwitcher; // Will be connected with the buttons via XML void onClick(View v){ switch (v.getId()) { case R.id.engplus: engcounter++; updateCounter(); break; case R.id.engneg: engcounter--; updateCounter(); break; } } private void updateCounter() { mSwitcher.setText(String.valueOf(engcounter)); } The .xml for this button is; <TextSwitcher android:id="@+id/eng_val" android:visibility="visible" android:paddingTop="9px" android:paddingLeft="50px" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/build" android:layout_toRightOf="@+id/engeq" android:textColor="#DD00ff00" android:textSize="24sp"/> This is within a Relative Layout that appears otherwise OK. When I had set the view to have a TextView with the number set as a string , the number displayed, but I could not figure out how to update the text with a numerical field. That may be my real problem. I have gone through many examples generally referenced from the dev. site (UI, Common Tasks, various samples), and I am still not seeing the connection here... Again, this is simply a try at getting variables to respond to buttons and update on the view. So, a few Q's for anyone that can help; 1) Is there any easier way of doing this (ie. send numerical value to View) ? 2) Why isn't my TextSwitcher displaying the number? 3) Should I be using a TextSwitcher here? 4) Any examples of this you can point me to?

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Persisting object changes from child form to parent form based on button press.

- by Shyran

I have created a form that is used for both adding and editing a custom object. Which mode the form takes is provided by an enum value passed from the calling code. I also pass in an object of the custom type. All of my controls at data bound to the specific properties of the custom object. When the form is in Add mode, this works great as when the controls are updated with data, the underlying object is as well. However, in Edit mode, I keep two variables of the custom object supplied by the calling code, the original, and a temporary one made through deep copying. The controls are then bound to the temporary copy, this makes it easy to discard the changes if the user clicks the Cancel button. What I want to know is how to persist those changes back to the original object if the user clicks the OK button, since there is now a disconnect because of the deep copying. I am trying to avoid implementing a internal property on the Add/Edit form if I can. Below is an example of my code: public AddEditCustomerDialog(Customer customer, DialogMode mode) { InitializeComponent(); InitializeCustomer(customer, mode); } private void InitializeCustomer(Customer customer, DialogMode mode) { this.customer = customer; if (mode == DialogMode.Edit) { this.Text = "Edit Customer"; this.tempCustomer = ObjectCopyHelper.DeepCopy(this.customer); this.customerListBindingSource.DataSource = this.tempCustomer; this.phoneListBindingSource.DataSource = this.tempCustomer.PhoneList; } else { this.customerListBindingSource.DataSource = this.customer; this.phoneListBindingSource.DataSource = this.customer.PhoneList; } }

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Unsure how to come up with a good design

- by Mewzer

Hello there, I am having trouble coming up with a good design for a group of classes and was hoping that someone could give me some guidance on best practices. I have kept the classes and member functions generic to make the problem simpler. Essentially, I have three classes (lets call them A, B, and C) as follows: class A { ... int GetX( void ) const { return x; }; int GetY( void ) const { return y; }; private: B b; // NOTE: A "has-a" B int x; int y; }; class B { ... void SetZ( int value ) { z = value }; private: int z; C c; // NOTE: B "has-a" C }; class C { private: ... void DoSomething(int x, int y){ ... }; void DoSomethingElse( int z ){ ... }; }; My problem is as follows: Class A uses its member variables "x" and "y" a lot internally. Class B uses its member variable "z" a lot internally. Class B needs to call C::DoSomething(), but C::DoSomething() needs the values of X and Y in class A passed in as arguments. C::DoSomethingElse() is called from say another class (e.g. D), but it needs to invoke SetZ() in class B!. As you can see, it is a bit of a mess as all the classes need information from one another!. Are there any design patterns I can use?. Any ideas would be much appreciated ....

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Read large amount of data from file in Java

- by Crozin

Hello I've got text file that contains 1 000 002 numbers in following formation: 123 456 1 2 3 4 5 6 .... 999999 100000 Now I need to read that data and allocate it to int variables (the very first two numbers) and all the rest (1 000 000 numbers) to an array int[]. It's not a hard task, but - it's horrible slow. My first attempt was java.util.Scanner: Scanner stdin = new Scanner(new File("./path")); int n = stdin.nextInt(); int t = stdin.nextInt(); int array[] = new array[n]; for (int i = 0; i < n; i++) { array[i] = stdin.nextInt(); } It works as excepted but it takes about 7500 ms to execute. I need to fetch that data in up to several hundred of milliseconds. Then I tried java.io.BufferedReader: Using BufferedReader.readLine() and String.split() I got the same results in about 1700 ms, but it's still too many. How can I read that amount of data in less that 1 second? The final result should be equal to: int n = 123; int t = 456; int array[] = { 1, 2, 3, 4, ..., 999999, 100000 };

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Does the Java Memory Model (JSR-133) imply that entering a monitor flushes the CPU data cache(s)?

- by Durandal

There is something that bugs me with the Java memory model (if i even understand everything correctly). If there are two threads A and B, there are no guarantees that B will ever see a value written by A, unless both A and B synchronize on the same monitor. For any system architecture that guarantees cache coherency between threads, there is no problem. But if the architecture does not support cache coherency in hardware, this essentially means that whenever a thread enters a monitor, all memory changes made before must be commited to main memory, and the cache must be invalidated. And it needs to be the entire data cache, not just a few lines, since the monitor has no information which variables in memory it guards. But that would surely impact performance of any application that needs to synchronize frequently (especially things like job queues with short running jobs). So can Java work reasonably well on architectures without hardware cache-coherency? If not, why doesn't the memory model make stronger guarantees about visibility? Wouldn't it be more efficient if the language would require information what is guarded by a monitor? As i see it the memory model gives us the worst of both worlds, the absolute need to synchronize, even if cache coherency is guaranteed in hardware, and on the other hand bad performance on incoherent architectures (full cache flushes). So shouldn't it be more strict (require information what is guarded by a monitor) or more lose and restrict potential platforms to cache-coherent architectures? As it is now, it doesn't make too much sense to me. Can somebody clear up why this specific memory model was choosen? EDIT: My use of strict and lose was a bad choice in retrospect. I used "strict" for the case where less guarantees are made and "lose" for the opposite. To avoid confusion, its probably better to speak in terms of stronger or weaker guarantees.

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Mathematics errors in basic C++ program

- by H Bomb1013

I am working with a basic C++ program to determine the area and perimeter of a rectangle. My program works fine for whole numbers but falls apart when I use any number with a decimal. I get the impression that I am leaving something out, but since I'm a complete beginner, I have no idea what. Below is the source: #include <iostream> using namespace std; int main() { // Declared variables int length; // declares variable for length int width; // declares variable for width int area; // declares variable for area int perimeter; // declares variable for perimeter // Statements cout << "Enter the length and the width of the rectangle: "; // states what information to enter cin >> length >> width; // user input of length and width cout << endl; // closes the input area = length * width; // calculates area of rectangle perimeter = 2 * (length + width); //calculates perimeter of rectangle cout << "The area of the rectangle = " << area << " square units." <<endl; // displays the calculation of the area cout << "The perimeter of the rectangle = " << perimeter << " units." << endl; // displays the calculation of the perimeter system ("pause"); // REMOVE BEFORE RELEASE - testing purposes only return 0; }

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Getting information from servlet created html

- by user541597

I have a servlet that creates an html text box and then redirects to another servlet on submit. How can I access the value of the html text box from the new servlet? I am able to access servlet variables from the new servlet but I am not aware of how to access the value of the html generated code. thanks, Here is the servlet that gets the text input public class ServletB extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); String value = System.getProperty("card"); PrintWriter out = response.getWriter(); out.println("<center><h1>Your preffered method of payment is "+value+"</h1><br />"); out.println("Please Enter Card Number<input type =\"text\" name = \"number\"/><form action=\"http://codd.cs.gsu.edu:9999/cpereyra183/servlet/ServletC\"><input type =\"submit\" value=\"Continue\" /><input type=\"button\" value=\"Cancel\" /></center>"); } }} This is the servlet the first servlet redirects to all I do is try to do is output the text input public class ServletC extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); String value = System.getProperty("card"); PrintWriter out = response.getWriter(); out.println(request.getParameter("number")); } }

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Prolog Beginner: How to unify with arithmentic cmparison operators or how to get a set var to range

- by sixtyfootersdude

I am new to prolog. I need to write an integer adder that will add numbers between 0-9 to other numbers 0-9 and produce a solution 0-18. This is what I want to do: add(in1, in2, out) :- in1 < 10, in2 < 10, out < 18. I would like to be able to call it like this: To Check if it is a valid addition: ?- add(1,2,3). true ?- add(1,2,4). false With one missing variable: ?- add(X,2,3). 1 ?- add(1,4,X). 5 With multiple missing variables: ?-add(X,Y,Z). % Some output that would make sense. Some examples could be: X=1, Y=1, Z=2 ; X=2, Y=1, Z=3 ...... I realize that this is probably a pretty simplistic question and it is probably very straightforward. However cording to the prolog tutorial I am using: "Unlike unification Arithmetic Comparison Operators operators cannot be used to give values to a variable. The can only be evaluated when every term on each side have been instantiated."

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Extracting exported functions out of a shared lib (ubuntu)

- by Pingu

the title already describes my problem. I found this post, but it didn't completely answers my question. With the help of it i got this output from nm... $nm -C -g -D ./libLoggingHandler.so 000000cc A _DYNAMIC ... 000042e0 T write_str(char*, char const*, int*) 00005a78 T RingBuffer::WriteUnlock() ... 00005918 T TraceLines::GetItemSize() ... U SharedMemory::attach(int, void const*, int) ... 00003810 T TraceProfile::FindLineNr(int, int) ... 00002d40 T LoggingHandler::getLogLevel() ... U SharedResource::getSharedResourceKey(char const*, int) ... which are the exported functions? I already found a hint in this post, that the "T" indicates that its getting exported. But if i check the nm manual here, it just says T - The symbol is in the text (code) section. My questions is: Does this output give me the information which functions are exported functions (or variables)? If not, how do i get it? Greetings, Pingu

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Android - update widget text

- by david

Hi, i have 2 questions about widgets update I have 2 buttons and i need to change one button text when i press the other one, how can i do this? The first time i open the widget it calls the onUpdate method, but it never calls it again. I need to update the widget every 2 seconds and i have this line in the xml. android:updatePeriodMillis="2000" Do i need a service or should it works just with the updatePeriodMillis tag? onUpdate method RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.newswidget); Intent intent = new Intent(context, DetalleConsulta.class); intent.putExtra(DetalleConsulta.CONSULTA_ID_NAME, "3"); PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0); views.setOnClickPendingIntent(R.id.btNews, pendingIntent); /* Inicializa variables para llamar el controlador */ this.imei = ((TelephonyManager)context.getSystemService(Context.TELEPHONY_SERVICE)).getDeviceId(); this.controlador = new Controlador(this.imei); try { this.respuestas = this.controlador.recuperarNuevasRespuestas(); if(this.respuestas != null && this.respuestas.size() > 0){ Iterator<Consulta> iterRespuestas = this.respuestas.iterator(); views.setTextViewText(R.id.btNews, ((Consulta)iterRespuestas.next()).getRespuesta()); } } catch (PersistenciaException e) { //TODO manejar error } appWidgetManager.updateAppWidget(appWidgetIds, views); thx a lot!!!

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game currency convert: math efficient

- by Comradsky

For variables:4 text views named diamondText, goldText, silverText, and bronzeText;money variable unsigned int money;and an NSTimer, every .1 sec,runs function: -(void)updateMoney{ money++; bronzeText.text = [NSString stringWithFormat:@"%d",money]; silverText.text = [NSString stringWithFormat:@"%d",money%10]; goldText.text = [NSString stringWithFormat:@"%d",money%100]; diamondText.text= [NSString stringWithFormat:@"%d",money%1000]; } Given that my currency is diamond = 10 gold = 10 silver = 10 bronze = 1; What would be most efficient way to calculate and display the money labels? How would you store this variable, with GameCenter and NSDictionary or GameCenter and something else? More details are below if you don't understand. To clarify: bronze has the last 2 numbers, silver has the next 2 numbers, and so on. I understand I could use 4 ints or an array, but i would rather try to use this method, unless theres a much more efficient way. Example: When money = 1000;bronzeText = nothing, silverText = 10,goldText = nothing, diamondText = nothing; What other ways would you do this that you think would be more efficient? I will be calling a function (void)collisionDetector that detects if my player.frame crosses with a flyingObject.frame, and if that object is a coin it gives an added value to money and then calls (void)updateMoney. Im just using the timer to test this and spawn these flying objects.

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ReplaceAll not working as expected

- by Tim Kemp

Still early days with Mathematica so please forgive what is probably a very obvious question. I am trying to generate some parametric plots. I have: ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} No joy: the replacement rules are not applied and a, b and h remain undefined. If I instead do: Hold@ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} it looks like the rules ARE working, as confirmed by the output: Hold[ParametricPlot[{(2 + 1) Cos[t] - 1 Cos[(2 + 1) t], (2 + 1) Sin[t] - 1 Sin[(2 + 1) t]}, {t, 0, 2 \[Pi]}, PlotRange -> All]] Which is what I'd expect. Take the Hold off, though, and the ParametricPlot doesn't work. There's nothing wrong with the equations or the ParametricPlot itself, though, because I tried setting values for a, b and h in a separate expression (a=2; b=1; h=1) and I get my pretty double cardoid out as expected. So, what am I doing wrong with ReplaceAll and why are the transformation rules not working? This is another fundamentally important aspect of MMA that my OOP-ruined brain isn't understanding. I tried reading up on ReplaceAll and ParametricPlot and the closest clue I found was that "ParametricPlot has attribute HoldAll and evaluates f only after assigning specific numerical values to variables" which didn't help much or I wouldn't be here. Thanks.

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Android Notepadv1 Tutorial - Persistent mNoteNumber?

- by Chris L.

So I did the Notepadv1 tutorial. It worked great. No problems. I would however like some explanation on why the mNoteNumber remembers the last number of the item I created. So the class starts as follows: public class Notepadv1 extends ListActivity { private int mNoteNumber = 1; That's fine, I understand that. The only other time the mNoteNumber variable is used is when you add an item it creates a note with that number and then increments it to the next number as follows: private void createNote() { String noteName = "Note " + mNoteNumber++; Those are the only two references to the variable mNoteNumber. When I press the Home button and then reopen the app, I add a new note but instead of adding a second "Note 1" it remembers that the last note I added as "Note 3" so it makes "Note 4". So I don't get it. Does Java/Android remember the last state of variables? If anyone could give me some explanation that would be great THANKS!

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sending address of a variable declared on the stack?

- by kobac

I have a doubt concerning declaring variables, their scope, and if their address could be sent to other functions even if they are declared on the stack? class A{ AA a; void f1(){ B b; aa.f2(&b); } }; class AA{ B* mb; f2(B* b){ mb = b; //... } }; Afterwards, I use my AA::mb pointer in the code. So things I would like to know are following. When the program exits A::f1() function, b variable since declared as a local variable and placed on the stack, can't be used anymore afterwards. What happens with the validity of the AA::mb pointer? It contains the address of the local variable which could not be available anymore, so the pointer isn't valid anymore? If B class is a std::<vector>, and AA::mb is not a pointer anymore to that vector, but a vector collection itself for example. I would like to avoid copying all of it's contents in AA::f2() to a member AA::mb in line mb = b. Which solution would you recommend since I can't assign a pointer to it, because it'll be destroyed when the program exits AA::f2()

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Why do I get Error#2036 in flash AS3 and how to solve this?

- by sydas

I'm currently building an application in flash in relation to RSS/XML feeds for a project. I'm stuck at the moment because I keep getting this error: Error opening URL 'http://distilleryimage6.instagram.com/.jpg' Error #2044: Unhandled IOErrorEvent:. text=Error #2036: Load Never Completed. I know my string picURL is not functioning properly, but am I missing something that makes it not functional? This is my code: package { import flash.display.*; import flash.events.*; import flash.net.*; public class instagramFeed extends MovieClip { //link to #rit xml loader public var ritFileRequest = new URLRequest("http://instagram.com/tags/rit/feed/recent.rss"); public var ritXmlLoader = new URLLoader(); //link to #rochester xml loader // same as above public variables public function instagramFeed() { // constructor code trace("About to load..."); //Loads #rit hashtag xml data. ritXmlLoader.load(ritFileRequest); ritXmlLoader.addEventListener(Event.COMPLETE, displayRITInfo); } //focuses on data with #rit hashtag public function displayRITInfo(e:Event):void{ var ritInstagramData:XML = new XML(ritXmlLoader.data); var ritInfoList:XMLList = ritInstagramData.elements().item; trace(ritInfoList); //load the image var ritPic:String = ritInfoList.*::condition.@code; var picURL:String = "http://distilleryimage6.instagram.com/" + ritPic + ".jpg"; trace(picURL); //show the image on the stage! var ritImageRequest:URLRequest = new URLRequest(picURL); var ritImageLoader:Loader = new Loader(); ritImageLoader.load(ritImageRequest); addChild(ritImageLoader); ritImageLoader.x=200; ritImageLoader.y=100; ritImageLoader.scaleX = 3; ritImageLoader.scaleY = 3; } } }

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Can a member struct be zero-init from the constructor initializer list without calling memset?

- by selbie

Let's say I have the following structure declaration (simple struct with no constructor). struct Foo { int x; int y; int z; char szData[DATA_SIZE]; }; Now let's say this struct is a member of a C++ class as follows: class CFoobar { Foo _foo; public: CFoobar(); }; If I declare CFoobar's constructor as follows: CFoobar::CFoobar() { printf("_foo = {%d, %d, %d}\n", _foo.x, _foo.y,_foo.z); for (int x = 0; x < 100; x++) printf("%d\n", _foo.szData[x]); } As you would expect, when CFoobar's constructor runs, garbage data gets printed out Obviously, the easy fix is to memset or ZeroMemory &_foo. It's what I've always done... However, I did notice that if add _foo to the constructor's initialization list with no parameters as follows: CFoobar::CFoobar() : _foo() { That this appears to zero-out the member variables of _foo. At least that was the case with g++ on linux. Now here's my question: Is this standard C++, or is this compiler specific behavior? If it's standard behavior, can someone quote me a reference from an official source? Any "gotchas" in regards to implicit zero-init behavior with more complicated structs and classes?

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First Time Working With Others?

- by cam

I've been at my very first programming job for about 8 months now and I've learned incredible amounts so far. Unfortunately, I'm the sole developer for a small startup company for internal applications. For the first time ever though, I'll be handing off some of my projects to someone else when I leave this job. I've documented all my projects thoroughly (at least I think so), but I still feel nervous about someone else reading my code. For example, I've always done this sort of thing. for (int i = 0; i < blah.length; i++) { //Do stuff } Should I name 'i' something descriptive? It's only a temporary variable, and will only exist within that loop, and it seems that it's pretty obvious what the loop does with 'i'. This is just one example. Another one is that I name variables differently... I don't really conform to a standard of naming besides starting all private members with an underscore. Are there any resources that could show me how to make it easier for the next developer? Are there standards for this type of thing?

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How to put data from List<string []> to dataGridView

- by Kirill

Try to put some data from List to dataGridView, but have some problem with it. Currently have method, that return me required List - please see picture below code public List<string[]> ReadFromFileBooks() { List<string> myIdCollection = new List<string>(); List<string[]> resultColl = new List<string[]>(); if (chooise == "all") { if (File.Exists(filePath)) { using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read)) { StreamReader sr = new StreamReader(fs); string[] line = sr.ReadToEnd().Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries); foreach (string l in line) { string[] result = l.Split(','); foreach (string element in result) { myIdCollection.Add(element); } resultColl.Add(new string[] { myIdCollection[0], myIdCollection[1], myIdCollection[2], myIdCollection[3] }); myIdCollection.Clear(); } sr.Close(); return resultColl; } } .... this return to me required data in requred form (like list from arrays). After this, try to move it to the dataGridView, that already have 4 columns with names (because i'm sure, that no than 4 colums required) - please see pic below Try to put data in to dataGridView using next code private void radioButtonViewAll_CheckedChanged(object sender, EventArgs e) { TxtLibrary myList = new TxtLibrary(filePathBooks); myList.chooise = "all"; //myList.ReadFromFileBooks(); DataTable table = new DataTable(); foreach (var array in myList.ReadFromFileBooks()) { table.Rows.Add(array); } dataGridViewLibrary.DataSource = table; } But as result got error - "required more rows that exist in dataGridVIew", but accordint to what I'm see (pic above) q-ty of rows (4) equal q-ty of arrays element in List (4). Try to check result by putting additional temp variables - but it's ok - please see pic below Where I'm wrong? Maybe i use dataGridView not in correct way?

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Overhead of calling tiny functions from a tight inner loop? [C++]

- by John

Say you see a loop like this one: for(int i=0; i<thing.getParent().getObjectModel().getElements(SOME_TYPE).count(); ++i) { thing.getData().insert( thing.GetData().Count(), thing.getParent().getObjectModel().getElements(SOME_TYPE)[i].getName() ); } if this was Java I'd probably not think twice. But in performance-critical sections of C++, it makes me want to tinker with it... however I don't know if the compiler is smart enough to make it futile. This is a made up example but all it's doing is inserting strings into a container. Please don't assume any of these are STL types, think in general terms about the following: Is having a messy condition in the for loop going to get evaluated each time, or only once? If those get methods are simply returning references to member variables on the objects, will they be inlined away? Would you expect custom [] operators to get optimized at all? In other words is it worth the time (in performance only, not readability) to convert it to something like: ElementContainer &source = thing.getParent().getObjectModel().getElements(SOME_TYPE); int num = source.count(); Store &destination = thing.getData(); for(int i=0;i<num;++i) { destination.insert(thing.GetData().Count(), source[i].getName(); } Remember, this is a tight loop, called millions of times a second. What I wonder is if all this will shave a couple of cycles per loop or something more substantial? Yes I know the quote about "premature optimisation". And I know that profiling is important. But this is a more general question about modern compilers, Visual Studio in particular.

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Error compiling basic java code

- by Michael Younani

New to java. Practicing coding by following a book. Heres my code: class Motorcycle { //Three instance variables - make and color are strings. while a boolean refers to TRUE OR FLASE(in this case off or on) String make; String color; boolean engineState; void startEngine() { if (engineState == true) System.out.print("The engine is already on."); else { engineState = true; System.out.print("The engine is now on."); } void showAtts() { System.out.print("This motorcycle is a " + color + " " + make); if (engineState ==true) System.out.print("The engine is on."); else System.out.print("The engine is off."); } } } When I compile I get 2 errors: 1) illegal start of expression 2) ; expected I can't pin point the problem. If anyone can direct me or hint me please do.

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Updating Cells in a DataTable

- by Maxim Z.

I'm writing a small app to do a little processing on some cells in a CSV file I have. I've figured out how to read and write CSV files with a library I found online, but I'm having trouble: the library parses CSV files into a DataTable, but, when I try to change a cell of the table, it isn't saving the change in the table! Below is the code in question. I've separated the process into multiple variables and renamed some of the things to make it easier to debug for this question. Code Inside the loop: string debug1 = readIn.Rows[i].ItemArray[numColumnToCopyTo].ToString(); string debug2 = readIn.Rows[i].ItemArray[numColumnToCopyTo].ToString().Trim(); string debug3 = readIn.Rows[i].ItemArray[numColumnToCopyFrom].ToString().Trim(); string towrite = debug2 + ", " + debug3; readIn.Rows[i].ItemArray[numColumnToCopyTo] = (object)towrite; After the loop: readIn.AcceptChanges(); When I debug my code, I see that towrite is being formed correctly and everything's OK, except that the row isn't updated: why isn't it working? I have a feeling that I'm making a simple mistake here: the last time I worked with DataTables (quite a long time ago), I had similar problems. If you're wondering why I'm adding another comma in towrite, it's because I'm combining a street address field with a zip code field - I hope that's not messing anything up. My code is kind of messy, as I'm only trying to edit one file to make a small fix, so sorry.

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Which of the following Java coding fragments is better?

- by Simon

This isn't meant to be subjective, I am looking for reasons based on resource utilisation, compiler performance, GC performance etc. rather than elegance. Oh, and the position of brackets doesn't count, so no stylistic comments please. Take the following loop; Integer total = new Integer(0); Integer i; for (String str : string_list) { i = Integer.parse(str); total += i; } versus... Integer total = 0; for (String str : string_list) { Integer i = Integer.parse(str); total += i; } In the first one i is function scoped whereas in the second it is scoped in the loop. I have always thought (believed) that the first one would be more efficient because it just references an existing variable already allocated on the stack, whereas the second one would be pushing and popping i each iteration of the loop. There are quite a lot of other cases where I tend to scope variables more broadly than perhaps necessary so I thought I would ask here to clear up a gap in my knowledge. Also notice that assignment of the variable on initialisation either involving the new operator or not. Do any of these sorts of semi-stylistic semi-optimisations make any difference at all?

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