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How can a constructor be invoked at the time of inheritance in C Plus Plus?
Wiki User
∙ 7y ago
It cannot. Inheritance is a compile-time operation. Constructors are invoked at runtime at the point of instantiation.
Wiki User
∙ 7y ago
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How do you invoke the constructor function in c plus plus?
There is no such thing as a constructor function in C++ (constructors have no return value, not even void, and cannot be called like regular functions). Constructors are invoked rather than called directly, either by declaring a static variable of the class type, or via the C++ new operator.
Why you use constructor chaining?
Constructor ChainingWe know that constructors are invoked at runtime when you say new on some class type as follows:Lamborghini h = new Lamborghini();But what really happens when you say new Lamborghini() ? (Assume Lamborghini extends Car and Car extends Object.)1. Lamborghini constructor is invoked. Every constructor invokes the constructor of its superclass with an (implicit) call to super(),2. Car constructor is invoked (Car is the superclass of Lamborghini).3. Object constructor is invoked (Object is the ultimate superclass of all classes, so class Car extends Object even though you don't actually type "extends Object" into the Car class declaration. It's implicit.) At this point we're on the top of the hierarchy.4. Object instance variables are given their explicit values. By explicit values, we mean values that are assigned at the time the variables are declared, like "int x = 27", where "27" is the explicit value (as opposed to the default value) of the instance variable.5. Object constructor completes.6. Car instance variables are given their explicit values (if any).7. Car constructor completes.8. Lamborghini instance variables are given their explicit values (if any).9. Lamborghini constructor completes.
In what order are the class constructors called when a derived class object is created?
We know that constructors are invoked at runtime when you say new on some class type as follows: Lamborghini h = new Lamborghini(); But what really happens when you say new Lamborghini() ? (Assume Lamborghini extends Car and Car extends Object.) 1. Lamborghini constructor is invoked. Every constructor invokes the constructor of its superclass with an (implicit) call to super(), 2. Car constructor is invoked (Car is the superclass of Lamborghini). 3. Object constructor is invoked (Object is the ultimate superclass of all classes, so class Car extends Object even though you don't actually type "extends Object" into the Car class declaration. It's implicit.) At this point we're on the top of the hierarchy. 4. Object instance variables are given their explicit values. By explicit values, we mean values that are assigned at the time the variables are declared, like "int x = 27", where "27" is the explicit value (as opposed to the default value) of the instance variable. 5. Object constructor completes. 6. Car instance variables are given their explicit values (if any). 7. Car constructor completes. 8. Lamborghini instance variables are given their explicit values (if any). 9. Lamborghini constructor completes.
Can you override the constructor?
A constructor should be overloaded when there is a parameter with default value that is commonly used, or if it is possible that not all the information for creating the instance will be gathered all at once. As an example, say there is a class that describes bank accounts. Assuming I can choose to deposit or not deposit money under my name upon creating an account, there is a chance for a meaningful overload. One constructor could take in the name of the account owner and the initial balance as parameters; the overloaded constructor could just take the name as a parameter while setting the initial balance to zero.
How do we invoke a constructor?
In Java, objects are constructed. Every time you make a new object, at least one constructor is invoked. Every class has a constructor, although if you don't create one explicitly, the compiler will build one for you. Ex: class Test { public Test() { } // this is Test's constructor public void Test() { } // this is a badly named, // but legal, method } If you see the example above, you would have realized that the constructor looks a lot like methods. Below are the main distinguishing factors between the constructor and normal methods: 1. The Constructor's name is exactly the same as the name of the class 2. They do not have a return type (Please remember this. A Constructor cannot have a return type as part of the code) 3. Constructors cannot be static, abstract or final
Can a constructor be declared as virtual?
A constructor cannot be virtual because at the time when the constructor is invoked the virtual table would not be available in the memory. Hence we cannot have a virtual constructor. ## Constructor called implicitly not explicitly so constructor is not virtual.
What is the difference between a constructor and a thread?
These concepts are two different things. A 'Constructor' is a special method with the same class name and with no return type definition, invoked only when we create a new object (when we instantiate our object with the 'new' operator). An is used to initialize our object state (our instance variables). A thread is a separate process which runs in parallel (at the same time) in a program.
Do you have to declare a constructor every time you create a class?
Yes, If you don't a default constructor will be created for you.
Difference between method and constructor in java?
A constructor is technically a type of method, but it is a very special type. Whereas other methods can be used to do just about anything, the only purpose of a constructor method is to create an instance of the class that contains it, often with parameters passed to it through another part of the program. This instance is called an "object" and is a central part of not only Java, but other object-oriented languages as well. A constructor method always has the same name as its containing class, and does not have a return type. Think of it this way: a class in Java is like a generic blueprint for a house. Your instance variables are like different attributes of the house - how many bathrooms will your house have, what colour will it be? Once you decide on the exact specifications for your house, you can give those parameters to the construction company, which will actually create that house. That's what a constructor method does - takes input parameters (or, lacking them, sets defaults) and creates an object.
Can abstract class have constructors?
A constructor of a class in invoked when a object of that class is created. As an abstract class can't have an object, so we can't create a constructor of the abstract class. But we can create a constructor of a concrete subclass of that abstract class and we have to pass the object of that concrete subclass to the abstract class.
What is rand function in c plus plus?
The rand() function returns an integer (int) value that represents a pseudo-random number between 0 and RAND_MAX, RAND_MAX being a constant declared in the run-time library. Each time rand() is invoked, a different value is returned.
1 Explain the concepts of constructor and destructor Do you have to declare a constructor every time you create a class?
You only need a constructor if the default constructor will not suffice. Often times, it is useful to have a constructor that takes common parameters so that you do not have to write additional code. For example, a Point class might have a constructor for Point(int x, int y), which would be a shortcut for assigning x and y independently. Other classes may not need any default values assigned, and for this, it is acceptable to just use the default constructor. Finally, some classes are virtual, static, or abstract, and so may not need a constructor because the constructor is unnecessary (static), or may be defined elsewhere (virtual, abstract).
