class a
{
int x=2;
a()
{
x=0;
}
void main()
{
a obj=new a();
System.out.print(obj.a);
}
}
the above program will print the value of x as "0"
A class's constructor will have the same name of the class and no return type (not even void): class Example(){ Example() {printf("This is the constructor\n");} ~Example(){printf("This is the destructor\n");} };
no you can have a class with no public methods and even with a a private constructor public class Example { //constructor private Example(){ } }
None, zero. Example: new MyClass(); //and public classMyClass{} no constructor defined inside of MyClass
Implicitly: (i.e., you do not code for it, but works as if you did)calling the no-argument constructor of the subclass, and there is no explicitly "redirect" codes.Explicitly:a constructor with base() / super() in the implementation, even that invoked constructor required some arguments.C# example: public SubClass(string whatever) : base() {//...}
C++ permits us to achieve this objects bt passing argument to the constructor function when the object are created . The constructor that can take arguments are called parametrized constructors Example:- class abc { int m,n; public: abc(int x,int y); //paramererise constructor ................ ................. }; abc::abc(int x,int y) { m=x;n=y; }
No. Logic should never go in a constructor; constructors should only be used to instantiate and initialize object data.
Static Constructor - It is a special type of constructor, introduced with C#. It gets called before the creation of the first object of a class(probably at the time of loading an assembly). See example below. Example: public class SomeClass() { static SomeClass() { //Static members may be accessed from here //Code for Initialization } }
If you don't type a constructor into your class code, a default constructor will be automatically generated by the compiler. The default constructor is ALWAYS a no-arg constructor. (Obviously the compiler has no clue what all arguments you might want for your class. So it takes the safe way out with a no argument constructor) A no-arg constructor is not necessarily the default (i.e., compiler-supplied) constructor, although the default constructor is always a no-arg constructor. The default constructor is the one the compiler provides! While the default constructor is always a no-arg constructor, you're free to put in your own no-arg constructor.
You always should define default constructor for your class. You must also define a copy constructor for your class if there are any pointers in the class. While it is not mandatory, failure to provide a default constructor can result in bad behavior, and failure to provide a copy constructor when you have pointers in the class will result in bad behavior. For example, without a default constructor, the compiler will not fully initialize the attributes of the class. It will initialize the virtual function table, and call base class constructors, but that is all - the attributes could be random garbage. For another example, without a copy constructor, the compiler will generate one that simply makes a bit wise copy of the attributes. If these attributes contain pointers, then you have two pointers to the same object, not necessarily a good thing, especially if one of them get "deleted".
Parameterised constructors accept arguments while non parameterised constructors do not. Example : class A { A(){ // non parameterised ... } A(int b){ // parameterised ... } }
An empty constructor takes no arguments and calls the default constructor
The constructor of a class is automatically called when an instance of the class is created (using new in C++). The constructor method has the same name as the class that it is a part of. Constructors have no type and do not return anything. Similarly, the destructor is automatically called when the instance of the class is destroyed. The destructor is the same name as the class and is preceded by a tilde (~) For example: class Example { public: Example() // Constructor { printf("Object created\n"); } ~Example() // Destructor { printf("Object destroyed\n") } }; int main() { Example* x = new Example(); // Creates object, calls constructor delete x; // Calls destructor, deletes object return 0; }