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• Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

  - by mystify

  For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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• Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

  - by mystify

  For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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• Serialport List Read problem and NullReferenceException?

  - by Plumbum7

  Hello everybody, Using Microsoft VC# 2008 Express (little fact about me : non experience in c#, programskills further very beginnerlevel. This peace op program is to communicate with Zigbee switching walloutlets (switching, status info). and is downloaded from http://plugwiselib.codeplex.com/SourceControl/list/changesets The problem: NullRefferenceException was UnHandled private void port_DataReceived(object sender, SerialDataReceivedEventArgs e) {// Event for receiving data string txt = port.ReadExisting(); Console.WriteLine(txt); List<PlugwiseMessage> msg = reader.Read (Regex.Split (txt, "\r\n" )); //Console.WriteLine( msg ); DataReceived(sender, new System.EventArgs(), msg); VC# Marks the last line and says msg is empty. so i looked further. Msg come's from txt text is filled with "000002D200C133E1\r\nPutFifoUnicast 40 : Handle 722 :"< so it goes wrong in or reader.Read or in the List so i looked further: public List<PlugwiseMessage> Read(string[] serialData) { Console.WriteLine(serialData); List<PlugwiseMessage> output = new List<PlugwiseMessage>(); Console.WriteLine(output); Both (serialData) as (output); are empty. So can i assume that the problem is in: Read(string[] serialData) But now the questions, Is Read(string[] serialData) something which is a Windows.Refence or is is from a Method ? and IF this is so is this then reader.READ (how can i find this)? (answered my own question proberly)(method reader)(private PlugwiseReader reader) So why isn't is working trough the serialData ? or is it the List<PlugwiseMessage> part, but i have no idea how it is filled can sombody help me ?

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• Calling a class method within a method definition in the same class

  - by user1786288

  So I'm writing a program for an intro Java class. I'm defining a method to add two fractions together within the class Fraction. Fraction has 2 variables, numerator and denominator. Each of these variables has a setter and a getter. Anyway, I have a problem with my addition method, which is shown below. I've just sort of tried to implement it in a way that made sense, but I'm sure I did something with calling methods/using objects that doesn't work. public void add(Fraction fraction1, Fraction fraction2) { Fraction fraction3 = new Fraction(); int a = fraction1.getNumerator; int b = fraction1.getDenominator; int c = fraction2.getNumerator; int d = fraction2.getDenominator; fraction3.setNumerator((a * d) + (b * c)); fraction3.setDenominator(b * d); } I don't know if the problem is in the method definition, if I can use the object type that way, or if there's something else wrong. any help would be appreciated, and if I need to provide any information, I'll do so ASAP.

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• How to draw histogram in Processing

  - by theolc

  I have an arrayList and I would like to take the size of the ten arrayList elements and use the sizes to create a histogram. I understand processing coordinate system starts in the top left corner. My question is, how do I use the arrayList.size() values to start at 450 (based from a 500,500 window) and go upwards from there to create my histogram. The following is my function for the histogram, it is receiving as a parameter the arrayList called bins. void histogram(ArrayList[] bins) { //set window background(0,0,0); size(500,500); background(255,255,255); line(50,0,50,500); line(0,450,500,450); int i; for (i = 50; i <= 500; i+=45) { line(i,450,i,480); } for (i = 50; i <= 450; i+=45) { line(50,i,20,i); } } Thanks in adavance for any help and input!

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• memory management: am i doing something wrong here?

  - by z s

  Hi, In a very small number of cases in my iphone app, I get a crash after the for loop in the code below: ABAddressBookRef addressBookInit = ABAddressBookCreate(); CFMutableArrayRef abContacts = (CFMutableArrayRef)ABAddressBookCopyArrayOfAllPeople(addressBookInit); // get array of all contacts CFArraySortValues (abContacts, CFRangeMake(0, CFArrayGetCount(abContacts)), (CFComparatorFunction)ABPersonComparePeopleByName, (void *)ABPersonGetSortOrdering()); NSArray *copypeople = (NSArray *) abContacts; NSMutableArray *tempTheadlist = [[NSMutableArray alloc] init]; for (int i=0; i < copypeople.count; i++) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; ABRecordRef record = [copypeople objectAtIndex:i]; if (blah blah) [tempThreadList addObject: someObject]; [pool release]; } // POINT OF CRASH AFTER LOOP ENDS if (tempTheadlist.count > 0) [NSThread detachNewThreadSelector: @selector(loading_pictures:) toTarget:self withObject:tempTheadlist]; [tempTheadlist release]; [copypeople release]; CFRelease(addressBookInit); Any reason why it should crash at any point here?

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• ASP disable button during postback

  - by user667430

  I have a button which i am trying to add a css class to appear disabled once the user has clicked it. protected void Button_Continue_OnClick(object sender, EventArgs e) { Panel_Error.Visible = false; Literal_Error.Text = ""; if (RadioButton_Yes.Checked) { ...//if radio checked get text and process etc. } } My button onlick is above which simply processes a textbox filled on the page. My button looks like this: <asp:Button runat="server" ID="Button_Continue" CssClass="button dis small" Text="Continue" OnClick="Button_Continue_OnClick" ClientIDMode="Static" OnClientClick="return preventMult();" /> And my javscript is as follows: <script type="text/javascript"> var isSubmitted = false; function preventMult() { if (isSubmitted == false) { $('#Button_Continue').removeClass('ready'); $('#Button_Continue').addClass('disabled'); isSubmitted = true; return true; } else { return false; } } </script> The problem I am having is that the css class added works fine on the first postback, but after which my button onclick doesnt work and the button cant be clicked again if the user needs to resubmit the data if it is wrong Another problem I am having is that with a breakpoint in my method i notice that the method is fired twice on the click.

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• Question about permute-by-sorting

  - by davit-datuashvili

  In the book "Introduction to Algorithms", second edition, there is the following problem: Suppose we have some array: int a[] = {1,2,3,4} and some random priorities array: P = {36,3,97,19} and the goal is to permute the array a randomly using this priorities array. This is the pseudo code: PERMUTE-BY-SORTING (A) 1 n ? length[A] 2 for i ? 1 to n 3 do P[i] = RANDOM (1, n 3) 4 sort A, using P as sort keys 5 return A The result should be the permuted array: B={2, 4, 1, 3}; I have written this code: import java.util.*; public class Permute { public static void main (String[] args) { Random r = new Random(); int a[] = new int[] {1,2,3,4}; int n = a.length; int b[] = new int[a.length]; int p[] = new int[a.length]; for (int i=0; i<p.length; i++) { p[i] = r.nextInt(n*n*n) + 1; } // for (int i=0;i<p.length;i++){ // System.out.println(p[i]); //} } } How do I continue?

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• How to use CellRenderer for GregorianCalendar?

  - by HansDampf

  So I have been trying to use the example from Tutorial and change it so it fits my program. The getColumnValue method returns the object that holds the information that is supposed to be displayed. Is this the way to go or should it rather return the actual String to be displayed. I guess not because that way I would mix the presentation with the data, which I was trying to avoid. public class IssueTableFormat implements TableFormat<Appointment> { public int getColumnCount() { return 6; } public String getColumnName(int column) { if(column == 0) return "Datum"; else if(column == 1) return "Uhrzeit"; else if(column == 2) return "Nummer"; else if(column == 3) return "Name"; else if(column == 4) return "letzte Aktion"; else if(column == 5) return "Kommentar"; throw new IllegalStateException(); } public Object getColumnValue(Appointment issue, int column) { if(column == 0) return issue.getDate(); else if(column == 1) return issue.getDate(); else if(column == 2) return issue.getSample(); else if(column == 3) return issue.getSample(); else if(column == 4) return issue.getHistory(); else if(column == 5) return issue.getComment(); throw new IllegalStateException(); } } The column 0 and 1 contain a GregorianCalendar object, but I want column 0 to show the date and 1 to show the time. So I know using cellRenderers can help here. This is what I tried. public class DateRenderer extends DefaultTableCellRenderer { public DateRenderer() { super(); } public void setValue(Object value) { GregorianCalendar g =(GregorianCalendar) value; value=g.get(GregorianCalendar.HOUR); } } But the cell doesnt show anything, what is wrong here?

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• ( Sql Server 2005 C#.Net ) - I want just the insert query for a temp table.

  - by John Stephen

  Hi..I am using C#.Net and Sql Server ( Windows Application ). I had created a temporary table. When a button is clicked, temporary table (#tmp_emp_details) is created. I am having another button called "insert Values" and also 5 textboxes. The values that are entered in the textbox are used and whenever com.ExecuteNonQuery(); line comes, it throws an error message called "Invalid object name '#tbl_emp_answer'.". Below is the set of code..Please give me a solution. Code for insert (in insert value button): private void btninsertvalues_Click(object sender, EventArgs e) { username = txtusername.Text; examloginid = txtexamloginid.Text; question = txtquestion.Text; answer = txtanswer.Text; useranswer = txtanswer.Text; SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=tempdb;Integrated Security=True;"); SqlCommand com = new SqlCommand("Insert into #tbl_emp_answer values('"+username+"','"+examloginid+"','"+question+"','"+answer+"','"+useranswer+"')", con); con.Open(); com.ExecuteNonQuery(); con.Close(); }

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• How can I make my code work in a GUI using Swing in Java?

  - by Razor Shadow

  I'm making a tool that does multiple things, and I'm onto the last feature for now: You type in a date and it tells you what day of the week it would be on that date. So I have two problems here: I can't use I can't use arguments, it doesn't like them On the last line, I can't use jTextArea2.setText(d0); because it doesn't like that either... My code is here: public static void main(String[] args) { int d = Integer.parseInt(args[0]); int m = Integer.parseInt(args[1]); int y = Integer.parseInt(args[2]); int y0 = y - (14 - m) / 12; int x = y0 + y0/4 - y0/100 + y0/400; int m0 = m + 12 * ((14 - m) / 12) - 2; int d0 = (d + x + (31*m0)/12) % 7; System.out.println("Sunday = 0\nMonday = 1\nTuesday = 2\nWednesday = 3\nThursday = 4\nFriday = 5\nSaturday = 6\nThis date is on a:"); System.out.println(d0); Basically, this code was at first for use with the console, and now I want to implement it into a Swing GUI app. I'm only a week into learning Java, so excuse me if the problem is obvious or easy to fix... But can anyone figure out how to work it? Thanks!

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• Something missing

  - by DHF

  The error of "} expected" appears at line 5. Why is that? I have included it at line 15. The error of "Declaration missing ;" appears at line 8. Why? There is ";" at the end of the line. #include<iostream> using namespace std; class PEmployee { public: PEmployee(); PEmployee(string employee_name, double initial_salary); void set_salary(double new_salary); double get_salary() const; string get_name() const; private: Person person_data; double salary; }; //line 15 int main() { PEmployee f("Patrick", 1000.00); cout << f.get_name() << " earns a salary of " << f.get_salary() << endl; return 0; } Newbie here, sorry for unclear question

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• Equvalent c++0x program withought using boost threads..

  - by Eternal Learner

  I have the below simple program using boost threads, what would be the changes needed to do the same in c++0X #include<iostream> #include<boost/thread/thread.hpp> boost::mutex mutex; struct count { count(int i): id(i){} void operator()() { boost::mutex::scoped_lock lk(mutex); for(int i = 0 ; i < 10000 ; i++) { std::cout<<"Thread "<<id<<"has been called "<<i<<" Times"<<std::endl; } } private: int id; }; int main() { boost::thread thr1(count(1)); boost::thread thr2(count(2)); boost::thread thr3(count(3)); thr1.join(); thr2.join(); thr3.join(); return 0; }

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• Force calling the derived class implementation within a generic function in C#?

  - by Adam Hardy

  Ok so I'm currently working with a set of classes that I don't have control over in some pretty generic functions using these objects. Instead of writing literally tens of functions that essentially do the same thing for each class I decided to use a generic function instead. Now the classes I'm dealing with are a little weird in that the derived classes share many of the same properties but the base class that they are derived from doesn't. One such property example is .Parent which exists on a huge number of derived classes but not on the base class and it is this property that I need to use. For ease of understanding I've created a small example as follows: class StandardBaseClass {} // These are simulating the SMO objects class StandardDerivedClass : StandardBaseClass { public object Parent { get; set; } } static class Extensions { public static object GetParent(this StandardDerivedClass sdc) { return sdc.Parent; } public static object GetParent(this StandardBaseClass sbc) { throw new NotImplementedException("StandardBaseClass does not contain a property Parent"); } // This is the Generic function I'm trying to write and need the Parent property. public static void DoSomething<T>(T foo) where T : StandardBaseClass { object Parent = ((T)foo).GetParent(); } } In the above example calling DoSomething() will throw the NotImplemented Exception in the base class's implementation of GetParent(), even though I'm forcing the cast to T which is a StandardDerivedClass. This is contrary to other casting behaviour where by downcasting will force the use of the base class's implementation. I see this behaviour as a bug. Has anyone else out there encountered this?

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• How to multi-thread this?

  - by WilliamKF

  I wish to have two threads. The first thread1 occasionally calls the following pseudo function: void waitForThread2() { if (thread2 is not idle) { return; } notifyThread2IamReady(); while (thread2IsExclusive) { } } The second thread2 is forever in the following pseudo loop: for (;;) { Notify thread1 I am idle. while (!thread1IsReady()) { } Notify thread1 I am exclusive. Do some work while thread1 is blocked. Notify thread1 I am busy. Do some work in parallel with thread1. } What is the best way to write this such that both thread1 and thread2 are kept as busy as possible on a machine with multiple cores. I would like to avoid long delays between notification in one thread and detection by the other. I tried using pthread condition variables but found the delay between thread2 doing 'notify thread1 I am busy' and the loop in waitForThread2() on thear2IsExclusive() can be up to almost one second delay. I then tried using a volatile sig_atomic_t shared variable to control the same, but something is going wrong, so I must not be doing it correctly.

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• Validation Logic

  - by user2961971

  I am trying to create some validation for a form I have. There are two text boxes and two radio buttons on the form. My logic for this validation I know is a little rusty at the moment so any suggestions would be great. Here is the code for what I have so far: Keep in mind that the int errors is a public variable in the class Start Button code: private void btnStart_Click(object sender, EventArgs e) { errors = validateForm(); //Here I want the user to be able to fix any errors where I am little stuck on that logic at the moment //validate the form while (errors > 0) { validateForm(); errors = validateForm(); } } ValidateForm Method: private int validateForm() { errors = 0; //check the form if there are any unentered values if (txtDest.Text == "") { errors++; } if (txtExt.Text == "") { errors++; } if (validateRadioBtns() == true) { errors++; } return errors; } ValidateRadioBtns Method: private Boolean validateRadioBtns() { //flag - false: selected, true: none selected Boolean blnFlag = false; //both of the radio buttons are unchecked if (radAll.Checked == false && radOther.Checked == false) { blnFlag = true; } //check if there is a value entered in the text box if other is checked else if(radOther.Checked == true && txtExt.Text == "") { blnFlag = true; } return blnFlag; } Overall I feel like this can somehow be more stream lined which I am fairly stuck on. Also, I am stuck on how to ensure the user can return to the form, fix the errors, and then validate again to ensure said errors are fixed. Any suggestions would be greatly appreciated since I know this is such a nooby question.

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• 2 bucks for !! java basic question

  - by Max

  How can I get a specific value from an object? I'm trying to get a value of an instance for eg. ListOfPpl newListOfPpl = new ListOfPpl(id, name, age); Object item = newListOfPpl; How can I get a value of name from an Object item?? Even if it is easy or does not interest you can anyone help me?? Edited: I was trying to build a binary tree contains the node of ListOfPpl, and need to sort it in the lexicographic. Here's my code for insertion on the node. Any clue?? public void insert(Object item){ Node current = root; Node follow = null; if(!isEmpty()){ root = new Node(item, null, null); return; }boolean left = false, right = false; while(current != null){ follow = current; left = false; right = false; //I need to compare and sort it if(item.compareTo(current.getFighter()) < 0){ current = current.getLeft(); left = true; }else { current = current.getRight(); right = true; } }if(left) follow.setLeft(new Node(item, null, null)); else follow.setRight(new Node(item, null, null)); }

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• Cannot connect to mysql via servlet

  - by JBoy

  Hi all I have been since 2 days trying to figure out why my servlet does not connect to the database MySql. I have mysql installed and working properly and eclipse. Whenever i try to etabilish a connection i get the ClassNotFoundException for the com.mysql.jdbc.Driver, which is actually properly imported, the connector i'm using is the mysql-connector-java5.1.14 added properly as external jar so everything seems fine. here's my code protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String dbUrl="jdbc:mysql://localhost:3306/test"; String username="root"; String password=""; try { Class.forName("com.mysql.jdbc.Driver").newInstance(); conn=DriverManager.getConnection(dbUrl); System.out.println("Connected!"); } catch (SQLException e) { e.printStackTrace(); System.out.println("not connected"); } catch(ClassNotFoundException x){ x.printStackTrace(); } catch(Exception e){ e.printStackTrace(); } } The stacktrace(part of): java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1645) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1491) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:375) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:164) i'm following the connection steps from a published java book and also in forums and tutorials i just see the same code, cannot figure out why that Exception comes. On a normal application which does not run on the server the Exception isn't thrown and the connection (in the exact same way) its successfull. Do you have any advice?

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• Dynamically adding custom view to RemoteViews

  - by Naidu

  Could any help me to do this?My code is like: public CustomClass extends View { //uses ondraw() to do something } For displaying my custom view on HomeScreen i created a class to extend Broadcast Receiver public class customAppWidgetProvider extends BroadcastReceiver { public void onReceive(Context context, Intent intent) { String action = intent.getAction(); if (AppWidgetManager.ACTION_APPWIDGET_UPDATE.equals(action)) { RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.main); //Here i want to create my custom view class object and i want to add this view to linear layout in main.xml CustomClass object = new CustomClass(context) ; LinearLayout layout = new LinearLayout(context) ; layout.setLayoutParameters(new LayoutParameters(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT)); layout.addView(object); views.addview(R.id.linearlayout, (ViewGroup) layout) ; views.setOnClickPendingIntent(R.id.analog_appwidget, PendingIntent.getActivity(context, 0, new Intent(context, AlarmClock.class), PendingIntent.FLAG_CANCEL_CURRENT)); int[] appWidgetIds = intent.getIntArrayExtra( AppWidgetManager.EXTRA_APPWIDGET_IDS); AppWidgetManager gm = AppWidgetManager.getInstance(context); gm.updateAppWidget(appWidgetIds, views); } } } But adding viewgroup to RemoteView reference is not working... above main.xml contains only LinearLayout.I want to add custom view object to it.But after running this not showing anything on screen.. please help me to do this.Thanks in Advance.

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• Creating a assertClass() method in JUnit

  - by Mike

  Hi, I'm creating a test platform for a protocol project based on Apache MINA. In MINA when you receive packets the messageReceived() method gets an Object. Ideally I'd like to use a JUnit method assertClass(), however it doesn't exist. I'm playing around trying to work out what is the closest I can get. I'm trying to find something similar to instanceof. Currently I have: public void assertClass(String msg, Class expected, Object given) { if(!expected.isInstance(given)) Assert.fail(msg); } To call this: assertClass("Packet type is correct", SomePacket.class, receivedPacket); This works without issue, however in experimenting and playing with this my interest was peaked by the instanceof operator. if (receivedPacket instanceof SomePacket) { .. } How is instanceof able to use SomePacket to reference the object at hand? It's not an instance of an object, its not a class, what is it?! Once establishing what type SomePacket is at that point is it possible to extend my assertClass() to not have to include the SomePacket.class argument, instead favouring SomePacket?

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• Template access of symbol in unnamed namespace

  - by Fred Larson

  We are upgrading our XL C/C++ compiler from V8.0 to V10.1 and found some code that is now giving us an error, even though it compiled under V8.0. Here's a minimal example: test.h: #include <iostream> #include <string> template <class T> void f() { std::cout << TEST << std::endl; } test.cpp: #include <string> #include "test.h" namespace { std::string TEST = "test"; } int main() { f<int>(); return 0; } Under V10.1, we get the following error: "test.h", line 7.16: 1540-0274 (S) The name lookup for "TEST" did not find a declaration. "test.cpp", line 6.15: 1540-1303 (I) "std::string TEST" is not visible. "test.h", line 5.6: 1540-0700 (I) The previous message was produced while processing "f<int>()". "test.cpp", line 11.3: 1540-0700 (I) The previous message was produced while processing "main()". We found a similar difference between g++ 3.3.2 and 4.3.2. I also found in g++, if I move the #include "test.h" to be after the unnamed namespace declaration, the compile error goes away. So here's my question: what does the Standard say about this? When a template is instantiated, is that instance considered to be declared at the point where the template itself was declared, or is the standard not that clear on this point? I did some looking though the n2461.pdf draft, but didn't really come up with anything definitive.

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• Trying to instantiate a class member in C++ with a variable name

  - by MarcZero

  Hello. I am writing a program for class that is asking us to create a class of "book". We are then supposed to create new instantiations of that class upon demand from the user. I am new to C++ so I am attempting to code this out but am running into a problem. The main problem is how do I instantiate a class with a variable if I don't know how many I will have to do ahead of time. The user could ask to add 1 book or 1000. I am looking at this basic code: This is the simple code I started with. I wanted to have an index int keep a number and have the book class I create be called by that int (0, 1, 2, etc...) So I attempted to convert the incoming index int into a string, but I'm kind of stuck from here. void addBook(int index){ string bookName; std::stringstream ss; ss << index; book bookName; cout << "Enter the Books Title: "; cin >> bookName.title; } But obviously this doesn't work as "bookName" is a string to the computer and not the class member I tried to create. All of the tutorials I have seen online and in my text show the classes being instantiated with names in the code, but I just don't know how to make it variable so I can create any amount of "books" that the user might want. Any insight on this would be appreciated. Thank you for your time.

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• how to count multiples of numbers in an input file?

  - by user292489

  i was trying to count the number of multiples of 2, 3, and 6 respectielly from the users input file. but for some reason, my counter is not working. can any bosy hep me please. my code: #include <stdio.h> int main (void) { int num[12]; int i; int counttwo; int countthree; int countsix; int total=0; printf("enter 12 integer numbers:\n"); for(i=0;i<12;i++){ scanf("%d", &num[i]); } for(i=0;i<12;i++){ counttwo=0; if(num[i]%2==0){ counttwo++; } countthree=0; if(num[i]%3==0) { countthree++; } countsix=0; if(num[i]%6==0) { countsix++; } printf("There are %d multiples of 2:\n", counttwo); printf("There are %d multiples of 3:\n", countthree); printf("There are %d multiples of 6:\n", countsix); } return 0; }

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• Picture.writeToStream() not writing out all bitmaps

  - by quickdraw mcgraw

  I'm using webview.capturePicture() to create a Picture object that contains all the drawing objects for a webpage. I can successfully render this Picture object to a bitmap using the canvas.drawPicture(picture, dst) with no problems. However when I use picture.writeToStream(fos) to serialize the picture object out to file, and then Picture.createFromStream(fis) to read the data back in and create a new picture object, the resultant bitmap when rendered as above is missing any larger images (anything over around 20KB! by observation). This occurs on all the Android OS platforms that I have tested 1.5, 1.6 and 2.1. Looking at the native code for Skia which is the underlying Android graphics library and the output file produced from the picture.writeToStream() I can see how the file format is constructed. I can see that some of the images in this Skia spool file are not being written out (the larger ones), the code that appears to be the problem is in skBitmap.cpp in the method void SkBitmap::flatten(SkFlattenableWriteBuffer& buffer) const; It writes out the bitmap fWidth, fHeight, fRowBytes, FConfig and isOpaque values but then just writes out SERIALIZE_PIXELTYPE_NONE (0). This means that the spool file does not contain any pixel information about the actual image and therefore cannot restore the picture object correctly. Effectively this renders the writeToStream and createFromStream() APIs useless as they do not reliably store and recreate the picture data. Has anybody else seen this behaviour and if so am I using the API incorrectly, can it be worked around, is there an explanation i.e. incomplete API / bug and if so are there any plans for a fix in a future release of Android? Thanks in advance.

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• Timer C#. Start, stop, and get the amount of time between the calls

  - by user1886060

  I'm writing UDP chat with reliable data transfer. I need to start a timer when a packet is sent, and stop it as soon it receives an answer from the server(ACK- acknowledgment). Here is my code: private void sendButton_Click(object sender, EventArgs e) { Packet snd = new Packet(ack, textBox1.Text.Trim()); textBox1.Text = string.Empty; Smsg = snd.GetDataStream();//convert message into array of bytes to send. while (true) { try { // Here I need to Start a timer! clientSock.SendTo(Smsg, servEP); clientSock.ReceiveFrom(Rmsg, ref servEP); //Here I need to stop a timer and get elapsed amount of time. Packet rcv = new Packet(Rmsg); if (Rmsg != null && rcv.ACK01 != ack) continue; if (Rmsg != null && rcv.ACK01 == ack) { this.displayMessageDelegate("ack is received :"+ack); ChangeAck(ack); break; } Thank you.

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