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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 else can I help you with?
How can you identify a constructor from among any other methods in a class?
Constructors have the same identifier as that of the class, so if the name of your class is Book then your constructor must also be named Book. Constructors have no return type, not even void.
What is an abstract class Write the syntax Declare a pure virtual function in an abstract class?
an abstract class is nothing but class which contains both abstract and concrete methods for abstract class we r nt create object Syntax for pure abstract class is abstract class x { public void abstract y(); public void abstract z(); public void abc() { }
What is the difference between abstract class and normal class?
Any class which has one or more abstract methods is called an abstract class. But in the normal class we can't have any abstract methods. We cannot create an object for the abstract classes. When we inherit the abstract class we should implement the abstract method which we inherit.
How do you call an abstract class from main method?
An abstract class cannot have a constructor and hence you cannot invoke the constructor of the class - i.e., you can instantiate an abstract class and hence you cannot call the constructor of an abstract class.
How many constructors does class Exception have?
The Exception class has 4 constructors. They are: a. Exception() b. Exception(String arg) c. Exception(String arg, Throwable arg1) d. Exception(Throwable arg)
What are different type of constructor in java?
Every class, including abstract classes, MUST have a constructor. The different types are: a. Regular constructors b. Overloaded constructors and c. Private constructors
What happens if an abstract modifier is applied to class. Explain?
The classes which have one or more abstract methods are abstract. To declare a class as abstract, use the abstract keyword in front of the class keyword, before the class declaration. Abstract classes cannot be instantiated. Similarly the new keyword cannot be used to create an object of the abstract class. Remember that the constructors and static variables cannot be declared as abstract. Any subclass of an abstract class must either implement all of the abstract methods in the superclass or be itself declared abstract.
For what purpose constructors are used in Java?
Constructors are used to create the instance of a class.
What is the use of constructors?
Constructors are used in object-oriented programming languages to create usable instances of abstract data types (classes).
What is the order of constructors and destructors of object?
The order of constructors is determined by the sequence they are called in the code, starting with the base class constructor and moving to the derived class constructor. Destructors are called in the reverse order of constructors, starting with the derived class destructor and moving to the base class destructor.
What is the similarity between abstract class and class?
They provide the same level of abstraction and encapsulation, and similar inheritance. The differences in inheritance: an abstract class forces you to have at least 1 subclass (otherwise this abstraction branch is useless, because you won't be able to create any instance), while a non-abstract class may have optional subclasses.
How can you identify a constructor from among any other methods in a class?
Constructors have the same identifier as that of the class, so if the name of your class is Book then your constructor must also be named Book. Constructors have no return type, not even void.
What is an abstract class Write the syntax Declare a pure virtual function in an abstract class?
an abstract class is nothing but class which contains both abstract and concrete methods for abstract class we r nt create object Syntax for pure abstract class is abstract class x { public void abstract y(); public void abstract z(); public void abc() { }
What is the difference between abstract class and normal class?
Any class which has one or more abstract methods is called an abstract class. But in the normal class we can't have any abstract methods. We cannot create an object for the abstract classes. When we inherit the abstract class we should implement the abstract method which we inherit.
Why you use constructors?
To create an instance of the class that implementing that constructor
What is main advantage of using constructors in java?
Constructors have the same name as the class itself and they do not specify a return type, not even void because they return the instance of the class itself. Because constructors have the same name as the class then they allow method overloading and also save memory and execution time of program. Program release memory of constructors function after using this function and it reduce program complexity.
How do you call an abstract class from main method?
An abstract class cannot have a constructor and hence you cannot invoke the constructor of the class - i.e., you can instantiate an abstract class and hence you cannot call the constructor of an abstract class.
