variable-initialization

问题 As it pertains to Delphi... When a variable is declare of a certain type, is it initialized to an OBJECT of that type? Or must the variable be assigned an expression which returns an object of that type? I'm coming from a strong Java background. What I mean to ask is this... In Java, say you declare an instance variable of a user defined type named Orange. Which would look like this: private Orange _fruit; The variable _fruit still holds a reference to null until actually assigned an instance

问题 I have the following code: int *numberArray = calloc(n, sizeof(int)); And I am unable to understand why I receive the following error. Cannot initialize a variable of type 'int *' with an rvalue of type 'void *'`. Thank you. 回答1: The compiler's error message is very clear. The return value of calloc is void* . You are assigning it to a variable of type int* . That is ok with a C program, but not with a C++ program. You can change that line to int* numberArray = (int*)calloc(n, sizeof(int));

问题 This question already has answers here : My attempt at value initialization is interpreted as a function declaration, and why doesn't A a(()); solve it? (5 answers) Closed 6 years ago . I have the following three class definitions: class String { public: String() {} String(const char *) {} }; class ClassA { public: ClassA(const String &) {} }; class ClassB { public: ClassB(const ClassA &, const String & = String()) {} void method() {} }; Now suppose I want to create an instance of ClassB :

问题 Foo f1 = Foo(); // (1) Ok Foo f2 = Foo; // (2) Compiler error Foo *p1 = new Foo(); // (3) Ok Foo *p2 = new Foo; // (4) Ok. Why?? I was wondering why there exists two ways to initialize pointers. It looks a little inconsistent. Is there some logical reason, and if so, what? Or, maybe it's some kind of legacy? And if so, What is the origin of such notation? 回答1: It's a bit... complicated, to say the least. When dealing with objects, both notations are equivalent. When dealing with primitive

问题 inside of the arrayAverage method, avg has the right value (I tested it by puting println (avg) inside of the method. When i call the method from my main method and then print avg, netbeans tells me that the variable may not have been initialized. I must be doing something wrong, but I cannot figure out what. /*****************************************************************************\ * randomIntCount | * program generates a list of random numbers from 1-10, calculates | * the frequency of

问题 I want to create a global variable called process without assigning anything to it in a first moment. Later on I'll spawn a new process in the operating system, and assign it to that variable. It can be done in C# like so: class TestCS { // creating a variable private System.Diagnostics.Process process; private void SomeMethod() { // assigning a newly spawned process to it process = Process.Start("file.exe", "-argument"); process.WaitForInputIdle(); } } I wrote the code below to accomplish

问题 To my surprise, I found that the name of a c++ object can be the same as class name. Can someone explain to me the reason why? When I declare an object of class a as a a1() , it does not raise an error, but doesn't call the constructor. Why is this happening? My code: #include<iostream> using namespace std; class a { public: a() { cout << "in a\n"; } }; int main() { a a1(); a a; } 回答1: When you write a a1(); it is actually being parsed as a function declaration not a call to the default

问题 I'm a relatively new student learning Java programming, but I'd like to ask for some help. The error I'm receiving in my code is stating "variable romanNumeral might not have been initialised." The intent for this program is for a user to enter a number from 1-39 and then have the appropriate roman numeral value displayed to the user via a dialog box. The code is not complete yet, as I've yet to find a solution to this problem due to the application not letting me compile my code. Here is the

问题 I wrote a simple C program and I was expecting that it will fail in compilation but unfortunately it compiles and runs fine in C, but fails in compilation in C++. Consider below program: #include <stdio.h> int main() { char *c=333; int *i=333; long *l=333; float *f=333; double *d=333; printf("c = %u, c+1 = %u",c,c+1); return 0; } Visit this link: http://ideone.com/vnKZnx I think that this program definitely can't compile in C++ due to C++'s strong type checking. Why this program compiles in C

问题 Which do you prefer and why" String myString = null; if(someCondition) myString = "something"; else myString = "something else"; OR String myString = ""; if(someCondition) myString = "something"; else myString = "something else"; I know that using the ternary (? :) operator is possible but I'd like to know about the above two. 回答1: Neither. Instead, this: String myString; if (someCondition) myString = "something"; else myString = "something else"; In both of your alternatives, the variable is