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  • null reference exception in the code

    - by LifeH2O
    I am getting NullReferenceException error on "_attr.Append(xmlNode.Attributes["name"]);". namespace SMAS { class Profiles { private XmlTextReader _profReader; private XmlDocument _profDoc; private const string Url = "http://localhost/teamprofiles.xml"; private const string XPath = "/teams/team-profile"; public XmlNodeList Teams{ get; private set; } private XmlAttributeCollection _attr; public ArrayList Team { get; private set; } public void GetTeams() { _profReader = new XmlTextReader(Url); _profDoc = new XmlDocument(); _profDoc.Load(_profReader); Teams = _profDoc.SelectNodes(XPath); foreach (XmlNode xmlNode in Teams) { _attr.Append(xmlNode.Attributes["name"]); } } } } the teamprofiles.xml file looks like <teams> <team-profile name="Australia"> <stats type="Test"> <span>1877-2010</span> <matches>721</matches> <won>339</won> <lost>186</lost> <tied>2</tied> <draw>194</draw> <percentage>47.01</percentage> </stats> <stats type="Twenty20"> <span>2005-2010</span> <matches>32</matches> <won>18</won> <lost>12</lost> <tied>1</tied> <draw>1</draw> <percentage>59.67</percentage> </stats> </team-profile> <team-profile name="Bangladesh"> <stats type="Test"> <span>2000-2010</span> <matches>66</matches> <won>3</won> <lost>57</lost> <tied>0</tied> <draw>6</draw> <percentage>4.54</percentage> </stats> </team-profile> </teams> I am trying to extract names of all teams in an ArrayList. Then i'll extract all stats of all teams and display them in my application. Can you please help me about that null reference exception?

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  • "Undefined reference to"

    - by user1332364
    I know that there are a lot of questions somewhat related to this one, but they answers are a bit hard for me to make sense of. I'm receiving the following error for a few different lines of code: C:\Users\Jeff\AppData\Local\Temp\ccAixtmT.o:football.cpp:(.text+0x6f0): undefined reference to `Player::set_values(int, std::string, float)' From these blocks of code: class Player { int playerNum; string playerPos; float playerRank; public: void set_values(int, string, float); float get_rank(){ return playerRank; }; bool operator == (const Player &p1/*, const Player &p2*/) const { if(&p1.playerNum == &playerNum && &p1.playerPos == &playerPos && &p1.playerRank == &playerRank) return true; else return false; }; }; And this being the main function referencing the subclass: int main() { ifstream infile; infile.open ("input.txt", ifstream::in); int numTeams; string command; while(!infile.fail() && !infile.eof()){ infile >> numTeams; string name; Player p; int playNum; string playPos; float playRank; Player all[11]; float ranks[11]; Team allTeams[numTeams]; for(int i=0; i<numTeams; i++){ infile >> name; for(int j=0; j<11; j++){ infile >> playNum; infile >> playPos; infile >> playRank; if(playPos == "QB") p.set_values(playNum, playPos, (playRank*2.0)); else if(playPos == "RB") p.set_values(playNum, playPos, (playRank*1.5)); else if(playPos == "WR") p.set_values(playNum, playPos, (playRank/1.8)); else if(playPos == "TE") p.set_values(playNum, playPos, (playRank*1.1)); else if(playPos == "GD") p.set_values(playNum, playPos, (playRank/2.0)); else if(playPos == "TC") p.set_values(playNum, playPos, (playRank/2.2)); else if(playPos == "CR") p.set_values(playNum, playPos, (playRank/1.2)); all[j] = p; allTeams[i].set_values(all, name); } } infile >> command; if (command == "play"){ int t1; int t2; infile >> t1; infile >> t2; play(allTeams[t1], allTeams[t2]); } else { int t1; int p1; int t2; int p2; swap(allTeams[t1], allTeams[t1].get_player(p1), allTeams[t2], allTeams[t2].get_player(p2)); } } }

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  • Object reference not set to an instance of an object- Linked List Example

    - by Zoro Roronoa
    I am seeing following errors : Object reference not set to an instance of an object! Check to determinate if the object is null before calling the method! I'am new with C#,and I made a program for Sorted Linked Lists. Here is the code where the error comes! public void Insert(double data) { Link newLink = new Link(data); Link current = first; Link previous = null; if (first == null) { first = newLink; } else { while (data > current.DData && current != null) { previous = current; current = current.Next; } previous.Next = newLink; newLink.Next = current; } } It says that the current referenc is null while (data current.DData && current != null), but I assigned it current = first; Please Help ! The rest is the complete code of the Program! class Link { double dData; Link next=null; public Link Next { get { return next; } set { next = value; } } public double DData { get { return dData; } set { dData = value; } } public Link(double dData) { this.dData = dData; } public void DisplayLink() { Console.WriteLine("Link : "+ dData); } } class SortedList { Link first; public SortedList() { first = null; } public bool IsEmpty() { return (this.first == null); } public void Insert(double data) { Link newLink = new Link(data); Link current = first; Link previous = null; if (first == null) { first = newLink; } else { while (data > current.DData && current != null) { previous = current; current = current.Next; } previous.Next = newLink; newLink.Next = current; } } public Link Remove() { Link temp = first; first = first.Next; return temp; } public void DisplayList() { Link current; current = first; Console.WriteLine("Display the List!"); while (current != null) { current.DisplayLink(); current = current.Next; } } } class SortedListApp { public void TestSortedList() { SortedList newList = new SortedList(); newList.Insert(20); newList.Insert(22); newList.Insert(100); newList.Insert(1000); newList.Insert(15); newList.Insert(11); newList.DisplayList(); newList.Remove(); newList.DisplayList(); } }

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  • mappedBy reference an unknown target entity property - hibernate error

    - by tommy
    first, my classes: User package com.patpuc.model; import java.util.List; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.OneToMany; import javax.persistence.Table; import com.patpuc.model.RolesMap; @Entity @Table(name = "users") public class User { @Id @Column(name = "USER_ID", unique = true, nullable = false) private int user_id; @Column(name = "NAME", nullable = false) private String name; @Column(name = "SURNAME", unique = true, nullable = false) private String surname; @Column(name = "USERNAME_U", unique = true, nullable = false) private String username_u; // zamiast username @Column(name = "PASSWORD", unique = true, nullable = false) private String password; @Column(name = "USER_DESCRIPTION", nullable = false) private String userDescription; @Column(name = "AUTHORITY", nullable = false) private String authority = "ROLE_USER"; @Column(name = "ENABLED", nullable = false) private int enabled; @OneToMany(mappedBy = "rUser") private List<RolesMap> rolesMap; public List<RolesMap> getRolesMap() { return rolesMap; } public void setRolesMap(List<RolesMap> rolesMap) { this.rolesMap = rolesMap; } /** * @return the user_id */ public int getUser_id() { return user_id; } /** * @param user_id * the user_id to set */ public void setUser_id(int user_id) { this.user_id = user_id; } /** * @return the name */ public String getName() { return name; } /** * @param name * the name to set */ public void setName(String name) { this.name = name; } /** * @return the surname */ public String getSurname() { return surname; } /** * @param surname * the surname to set */ public void setSurname(String surname) { this.surname = surname; } /** * @return the username_u */ public String getUsername_u() { return username_u; } /** * @param username_u * the username_u to set */ public void setUsername_u(String username_u) { this.username_u = username_u; } /** * @return the password */ public String getPassword() { return password; } /** * @param password * the password to set */ public void setPassword(String password) { this.password = password; } /** * @return the userDescription */ public String getUserDescription() { return userDescription; } /** * @param userDescription * the userDescription to set */ public void setUserDescription(String userDescription) { this.userDescription = userDescription; } /** * @return the authority */ public String getAuthority() { return authority; } /** * @param authority * the authority to set */ public void setAuthority(String authority) { this.authority = authority; } /** * @return the enabled */ public int getEnabled() { return enabled; } /** * @param enabled * the enabled to set */ public void setEnabled(int enabled) { this.enabled = enabled; } @Override public String toString() { StringBuffer strBuff = new StringBuffer(); strBuff.append("id : ").append(getUser_id()); strBuff.append(", name : ").append(getName()); strBuff.append(", surname : ").append(getSurname()); return strBuff.toString(); } } RolesMap.java package com.patpuc.model; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; import com.patpuc.model.User; @Entity @Table(name = "roles_map") public class RolesMap { private int rm_id; private String username_a; private String username_l; //private String username_u; private String password; private int role_id; @ManyToOne @JoinColumn(name="username_u", nullable=false) private User rUser; public RolesMap(){ } /** * @return the user */ public User getUser() { return rUser; } /** * @param user the user to set */ public void setUser(User rUser) { this.rUser = rUser; } @Id @Column(name = "RM_ID", unique = true, nullable = false) public int getRmId() { return rm_id; } public void setRmId(int rm_id) { this.rm_id = rm_id; } @Column(name = "USERNAME_A", unique = true) public String getUsernameA() { return username_a; } public void setUsernameA(String username_a) { this.username_a = username_a; } @Column(name = "USERNAME_L", unique = true) public String getUsernameL() { return username_l; } public void setUsernameL(String username_l) { this.username_l = username_l; } @Column(name = "PASSWORD", unique = true, nullable = false) public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Column(name = "ROLE_ID", unique = true, nullable = false) public int getRoleId() { return role_id; } public void setRoleId(int role_id) { this.role_id = role_id; } } when i try run this on server i have exception like this: Error creating bean with name 'SessionFactory' defined in ServletContext resource [/WEB-INF/classes/baseBeans.xml]: Invocation of init method failed; nested exception is org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: com.patpuc.model.RolesMap.users in com.patpuc.model.User.rolesMap But i don't exaclu know what i'm doing wrong. Can somebody help me fix this problem?

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  • Garbage collection in Perl

    - by srikfreak
    Unlike Java, Perl uses reference count for garbage collection. I have tried searching some previous questions which speak about C++ RAII and smart pointers and Java GC but have not understood how Perl deals with the circular referencing problem. Can anyone explain how Perl's garbage collector deals with circular references? Is there any way to reclaim circular referenced memory which are no longer used by the program or does Perl just ignores this problem altogether?

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  • Good JavaScript Books?

    - by jollyjerry
    I find myself using Javascript day to day without a solid understanding of the language. There are some great writeups out there about using specific features of the language, but I'd like a distilled, printed book reference about the language itself. Please list good books that discuss the JavaScript language; not frameworks, usage and quirks.

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  • Arrays multiplication

    - by mariO
    How to write arrayt multiplication (multiplicating two matrieces ie 3x3) of arrays of known size in c++ ? What will be the difference using pointers and reference ?

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  • How to get ref of an array in PHP 5 ?

    - by Relax
    In php 5, all variable and objects are passed by reference, but i can't get my codes work My codes is: $arrayA = array(); $array = $arrayA; ... if(!in_array(thedata, $array) // if i use & to get ref, got an error here, should i use *$array here? $array[] = thedata; var_dump($arrayA); The result is empty, am i missing something simple?

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  • Swap references at build time in VS

    - by NitroxDM
    I have a project that runs on both .NET and .NET CF. But it uses a 3rd party library that will not run on both. So I end up changing the reference every time the project gets built. Project A - References the 3rd party dll. Project B - References A and runs .NET CF Project C - References A and runs .NET Is there a way to automate it?

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  • References for better performance of newer JSF specifications

    - by Pentius
    Dear fellows, I'm looking for a reference to cite, which states that JSF 1.2 performs better than JSF 1.1. Or JSF 2.0 over JSF 1.2 respectively. I'm quite sure that I've read something like this before but can't find it anymore. Maybe you can help. Or is this mischief and there are no official statements regarding the performance?

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  • How to generate real UTF-8 XML with grails without the escape characters?

    - by AngeDeLaMort
    I have been wondering why when I set the encoding to UTF-8 and rendering the XML it replace the extended characters by escape characters (or character reference) like &#x2019; instead of '? I'm using the Render method render(contentType:"text/xml", encoding:"UTF-8") {...} with a proper header render(contentType:"text/xml", encoding:"UTF-8", text:"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n") Any idea if there is a way to write it properly? Thanks.

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  • How do I find out what android system icons mean?

    - by The Trav
    Ok, so I've got an andoid phone with a bunch of icons up the top, looks like app notifications go on the left, system icons go on the right. Most of the system icons seem reasonably intuitive, service, 3g, wireless etc. I've recently gotten a new one that looks like a phone being tilted / shaken and have absolutely no idea what it means. Is there a reference site where I can look this thing up?

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  • Undefined referencec to ...

    - by Patrick LaChance
    I keep getting this error message every time I try to compile, and I cannot find out what the problem is. any help would be greatly appreciated: C:\DOCUME~1\Patrick\LOCALS~1\Temp/ccL92mj9.o:main.cpp:(.txt+0x184): undefined reference to 'List::List()' C:\DOCUME~1\Patrick\LOCALS~1\Temp/ccL92mj9.o:main.cpp:(.txt+0x184): undefined reference to 'List::add(int)' collect2: ld returned 1 exit status code: //List.h ifndef LIST_H define LIST_H include //brief Definition of linked list class class List { public: /** \brief Exception for operating on empty list */ class Empty : public std::exception { public: virtual const char* what() const throw(); }; /** \brief Exception for invalid operations other than operating on an empty list */ class InvalidOperation : public std::exception { public: virtual const char* what() const throw(); }; /** \brief Node within List */ class Node { public: /** data element stored in this node */ int element; /** next node in list / Node next; /** previous node in list / Node previous; Node (int element); ~Node(); void print() const; void printDebug() const; }; List(); ~List(); void add(int element); void remove(int element); int first()const; int last()const; int removeFirst(); int removeLast(); bool isEmpty()const; int size()const; void printForward() const; void printReverse() const; void printDebug() const; /** enables extra output for debugging purposes */ static bool traceOn; private: /** head of list */ Node* head; /** tail of list */ Node* tail; /** count of number of nodes */ int count; }; endif //List.cpp I only included the parts of List.cpp that might be the issue include "List.h" include include using namespace std; List::List() { //List::size = NULL; head = NULL; tail = NULL; } List::~List() { Node* current; while(head != NULL) { current = head- next; delete current-previous; if (current-next!=NULL) { head = current; } else { delete current; } } } void List::add(int element) { Node* newNode; Node* current; newNode-element = element; if(newNode-element head-element) { current = head-next; } else { head-previous = newNode; newNode-next = head; newNode-previous = NULL; return; } while(newNode-element current-element) { current = current-next; } if(newNode-element <= current-element) { newNode-previous = current-previous; newNode-next = current; } } //main.cpp include "List.h" include include using namespace std; //void add(int element); int main (char** argv, int argc) { List* MyList = new List(); bool quit = false; string value; int element; while(quit==false) { cinvalue; if(value == "add") { cinelement; MyList-add(element); } if(value=="quit") { quit = true; } } return 0; } I'm doing everything I think I'm suppose to be doing. main.cpp isn't complete yet, just trying to get the add function to work first. Any help will be greatly appreciated.

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  • Java: how to avoid circual references when dumping object information with reflection?

    - by Tom
    I've modified an object dumping method to avoid circual references causing a StackOverflow error. This is what I ended up with: //returns all fields of the given object in a string public static String dumpFields(Object o, int callCount, ArrayList excludeList) { //add this object to the exclude list to avoid circual references in the future if (excludeList == null) excludeList = new ArrayList(); excludeList.add(o); callCount++; StringBuffer tabs = new StringBuffer(); for (int k = 0; k < callCount; k++) { tabs.append("\t"); } StringBuffer buffer = new StringBuffer(); Class oClass = o.getClass(); if (oClass.isArray()) { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("["); for (int i = 0; i < Array.getLength(o); i++) { if (i < 0) buffer.append(","); Object value = Array.get(o, i); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if (value.getClass().isPrimitive() || value.getClass() == java.lang.Long.class || value.getClass() == java.lang.String.class || value.getClass() == java.lang.Integer.class || value.getClass() == java.lang.Boolean.class) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } buffer.append(tabs.toString()); buffer.append("]\n"); } else { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("{\n"); while (oClass != null) { Field[] fields = oClass.getDeclaredFields(); for (int i = 0; i < fields.length; i++) { if (fields[i] == null) continue; buffer.append(tabs.toString()); fields[i].setAccessible(true); buffer.append(fields[i].getName()); buffer.append("="); try { Object value = fields[i].get(o); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if ((value.getClass().isPrimitive()) || (value.getClass() == java.lang.Long.class) || (value.getClass() == java.lang.String.class) || (value.getClass() == java.lang.Integer.class) || (value.getClass() == java.lang.Boolean.class)) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } catch (IllegalAccessException e) { System.out.println("IllegalAccessException: " + e.getMessage()); } buffer.append("\n"); } oClass = oClass.getSuperclass(); } buffer.append(tabs.toString()); buffer.append("}\n"); } return buffer.toString(); } The method is initially called like this: System.out.println(dumpFields(obj, 0, null); So, basically I added an excludeList which contains all the previousely checked objects. Now, if an object contains another object and that object links back to the original object, it should not follow that object further down the chain. However, my logic seems to have a flaw as I still get stuck in an infinite loop. Does anyone know why this is happening?

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  • Referencing variables in a structure / C++

    - by user1628622
    Below, I provided a minimal example of code I created. I managed to get this code working, but I'm not sure if the practice being employed is sound. In essence, what I am trying to do is have the 'Parameter' class reference select elements in the 'States' class, so variables in States can be changed via Parameters. Questions I have: is the approach taken OK? If not, is there a better way to achieve what I am aiming for? Example code: struct VAR_TYPE{ public: bool is_fixed; // If is_fixed = true, then variable is a parameter double value; // Numerical value std::string name; // Description of variable (to identify it by name) }; struct NODE{ public: VAR_TYPE X, Y, Z; /* VAR_TYPE is a structure of primitive types */ }; class States{ private: std::vector <NODE_ptr> node; // shared ptr to struct NODE std::vector <PROP_DICTIONARY_ptr> property; // CAN NOT be part of Parameter std::vector <ELEMENT_ptr> element; // CAN NOT be part of Parameter public: /* ect */ void set_X_reference ( Parameter &T , int i ) { T.push_var( &node[i]->X ); } void set_Y_reference ( Parameter &T , int i ) { T.push_var( &node[i]->Y ); } void set_Z_reference ( Parameter &T , int i ) { T.push_var( &node[i]->Z ); } bool get_node_bool_X( int i ) { return node[i]->X.is_fixed; } // repeat for Y and Z }; class Parameter{ private: std::vector <VAR_TYPE*> var; public: /* ect */ }; int main(){ States S; Parameter P; /* Here I initialize and set S, and do other stuff */ // Now I assign components in States to Parameters for(int n=0 ; n<S.size_of_nodes() ; n++ ){ if ( S.get_node_bool_X(n)==true ){ S.set_X_reference ( P , n ); }; // repeat if statement for Y and Z }; /* Now P points selected to data in S, and I can * modify the contents of S through P */ return 0; }; Update The reason this issue cropped up is I am working with Fortran legacy code. To sum up this Fotran code - it's a numerical simulation of a flight vehicle. This code has a fairly rigid procedural framework one must work within, which comes with a pre-defined list of allowable Fortran types. The Fortran glue code can create an instance of a C++ object (in actuality, a reference from the perspective of Fortran), but is not aware what is contained in it (other means are used to extract C++ data into Fortran). The problem that I encountered is when a C++ module is dynamically linked to the Fortran glue code, C++ objects have to be initialized each instance the C++ code is called. This happens by virtue of how the Fortran template is defined. To avoid this cycle of re-initializing objects, I plan to use 'State' as a container class. The Fortran code allows a 'State' object, which has an arbitrary definition; but I plan to use it to harness all relevant information about the model. The idea is to use the Parameters class (which is exposed and updated by the Fortran code) to update variables in States.

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  • CA2000 passing object reference to base constructor in C#

    - by Timothy
    I receive a warning when I run some code through Visual Studio's Code Analysis utility which I'm not sure how to resolve. Perhaps someone here has come across a similar issue, resolved it, and is willing to share their insight. I'm programming a custom-painted cell used in a DataGridView control. The code resembles: public class DataGridViewMyCustomColumn : DataGridViewColumn { public DataGridViewMyCustomColumn() : base(new DataGridViewMyCustomCell()) { } It generates the following warning: CA2000 : Microsoft.Reliability : In method 'DataGridViewMyCustomColumn.DataGridViewMyCustomColumn()' call System.IDisposable.Dispose on object 'new DataGridViewMyCustomCell()' before all references to it are out of scope. I understand it is warning me DataGridViewMyCustomCell (or a class that it inherits from) implements the IDisposable interface and the Dispose() method should be called to clean up any resources claimed by DataGridViewMyCustomCell when it is no longer. The examples I've seen on the internet suggest a using block to scope the lifetime of the object and have the system automatically dispose it, but base isn't recognized when moved into the body of the constructor so I can't write a using block around it... which I'm not sure I'd want to do anyway, since wouldn't that instruct the run time to free the object which could still be used later inside the base class? My question then, is the code okay as is? Or, how could it be refactored to resolve the warning? I don't want to suppress the warning unless it is truly appropriate to do so.

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