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A constructor is not a mandatory member that we need to code specifically for a class. While creating a class, even if we miss out coding the constructor, Java would create a default constructor all by itself.
The constructor is usually the place where we initialize things that are required by the class. Hence it is a good practice to code the constructor for our class.
Tip: If you do not want anyone to instantiate your class, you can declare the constructor as private. In that way no other class can instantiate your class.
Wiki User
∙ 15y ago
Wiki User
∙ 14y agoConstructors must be public so other classes can create instances of that class. If the constructors were private, no class can use it!
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In C plus plus What function is called to initialize a class?
Class initialisation is normally handled by the class constructor(s). Every constructor has an optional initialisation section between the declaration and the body of the constructor. This is generally used to call specific base class constructors, but can be used to initialise any member variables via their own constructors. Member variables may alternatively be initialised in the body of the constructor, but this is really only necessary when member pointers need to be allocated new memory. For those classes that have many members and many constructors, the initialisation may be handled by a private member method called by each constructor in order to simplify maintenance during development. However, when the class is finalised, the private member method will generally be replaced with formal initialisation sections in each constructor.
When a class uses dynamic memory what member function should be provided by class?
the copy constructor
Can you declare and define the constructor within class?
Yes, you can declare and define the constructor within a class. A constructor is a special member function of a class that is automatically called when an object of the class is created. It is used to initialize the object's data members. The constructor can be declared and defined within the class definition or can be defined outside the class definition using the scope resolution operator (::).
What is a constructor and its mandatory to use constructor in a class?
Constructor is a special block of code similar to the method that is used to initialize the state of objects. If you do not define a constructor in a class, Java compiler automatically put a default constructor in the class.
How do you get a default constructor?
The default constructor is an empty (only call the super constructor) with no parameters constructor inserted by the java compiler when you don't define a constructor in your class. If you write something like this: public class NoConstructorClass{ //no constructor goes here } Then you get something like this: public class NoConstructorClass{ public NoConstructorClass(){ // Default constructor that you didn't write super(); } }
What is constructor in cplusplus?
A constructor is a special member function which have same name as the class name.`
In C plus plus What function is called to initialize a class?
Class initialisation is normally handled by the class constructor(s). Every constructor has an optional initialisation section between the declaration and the body of the constructor. This is generally used to call specific base class constructors, but can be used to initialise any member variables via their own constructors. Member variables may alternatively be initialised in the body of the constructor, but this is really only necessary when member pointers need to be allocated new memory. For those classes that have many members and many constructors, the initialisation may be handled by a private member method called by each constructor in order to simplify maintenance during development. However, when the class is finalised, the private member method will generally be replaced with formal initialisation sections in each constructor.
When a class uses dynamic memory what member function should be provided by class?
the copy constructor
Can you declare and define the constructor within class?
Yes, you can declare and define the constructor within a class. A constructor is a special member function of a class that is automatically called when an object of the class is created. It is used to initialize the object's data members. The constructor can be declared and defined within the class definition or can be defined outside the class definition using the scope resolution operator (::).
How do you declare constructor in cpp?
More or less as you would any other function, except there is no return type (not even void) and an initialisation list can be placed between the declaration and the definition that follows it. The initialisation list allows your constructor to call base class constructors besides the default constructor as well as initialise member variables according to the parameters passed to your constructor. The constructor's name must be the name of the class. Note that if you don't declare any constructors, the compiler generates both a default and copy constructor. If any constructor is declared you lose the default constructor unless you declare one yourself. The copy constructor is always present but must be overridden if your class contains pointers to memory allocated to the class itself. If you don't, the compiler generated copy constructor will perform a member-wise copy of the member variables, resulting in a shallow copy of the pointers themselves, rather than a deep copy of the memory they point to. The copy constructor must accept a constant reference to the same class of object.
Why constructor rather than classes in java?
Constructor is not an alternative to class. In Java, you create classes; the classes contain methods - including the constructor, which can be viewed as a special method. If you want to have a constructor, you need a class that surrounds it, so it's not one or the other.
What is a constructor and its mandatory to use constructor in a class?
Constructor is a special block of code similar to the method that is used to initialize the state of objects. If you do not define a constructor in a class, Java compiler automatically put a default constructor in the class.
What happens when no constructor function is declared in a class - in Java?
When any constructor is deffined in your class, the java compiler create a default no argument constructor for you. This constructor only have an invocation to the super class constructor (" super( ) ").
Can you declare constructor as a private in c plus plus?
Yes. However, like any other private member, a private constructor can only be accessed by the class itself (typically via a static member function) or by one of its friends. There are very few cases where private constructors are appropriate, one of the most common being the need to suppress the compiler-generated copy construction of a base class. However, since C++11, suppressed constructors can simply be deleted, thus making error messages much more meaningful to users of your class. For example, instead of the following: class A { public: A (); // default constructor private: A (const A&); // suppress copy constructor (can still be invoked by the class and its friends) // ... }; You'd now use the following: class A { public: A (); // default constructor A (const A&) =delete; // suppress copy constructor (cannot be invoked at all) // ... };
How do you get a default constructor?
The default constructor is an empty (only call the super constructor) with no parameters constructor inserted by the java compiler when you don't define a constructor in your class. If you write something like this: public class NoConstructorClass{ //no constructor goes here } Then you get something like this: public class NoConstructorClass{ public NoConstructorClass(){ // Default constructor that you didn't write super(); } }
Do we need Always need constructor in every class?
Objects are constructed. You can't make a new object without invoking a constructor. In fact, you can't make a new object without invoking not just the constructor of the object's actual class type, but also the constructor of each of its superclasses including the Object class itself! Constructors are the code that runs whenever you use the keyword new.
What is the name of the special member function which is automatically called during creation of each class object?
The constructor. The constructor instantiates the object, and can optionally take parameters and has an optional initialization phase. It has no return type, and has the same name as the class itself. The constructor can be overloaded. It cannot be virtual or constant.
