When a class declares an entire class as its friend?
When a class declares an entire class as its friend, the friendship status is reciprocal. That is, each class’s member functions have free access to the other’s private members. By default, when an object is assigned to another, each member of one object is copied to its counterpart in the other object.
When a class contains an instance of another class it is known as?
You can ask ! When a class contains an instance of another class, it is known as object overloading operator overloading object composition dynamic composition… 8.
When you overload an operator you can change the operator’s original meaning to something different?
When you overload an operator, you can change the operator’s original meaning to something entirely different. C++ permits you to overload the sizeof operator and the this pointer. When you overload the << operator you must also overload the >> operator.
Which of the following operators may be used to assign one object to another?
The = operator may be used to assign one object’s data to another object, or to initialize one object with another object’s data. By default, each member of one object is copied to its counterpart in the other object.
How many constructors can a class have?
A class can have any number of constructors. If a class have more than one constructor, we call it as the constructor is overloaded.
Can constructor be overloaded?
Yes! Java supports constructor overloading. In constructor loading, we create multiple constructors with the same name but with different parameters types or with different no of parameters.
Can a class have multiple constructors?
A class can have multiple constructors, as long as their signature (the parameters they take) are not the same. You can define as many constructors as you need. This is what constructor overloading means, that a Java class contains multiple constructors.
Can a constructor be private?
Yes. Class can have private constructor. Even abstract class can have private constructor. By making constructor private, we prevent the class from being instantiated as well as subclassing of that class.
Can a constructor be static?
No, we cannot define a static constructor in Java, If we are trying to define a constructor with the static keyword a compile-time error will occur. In general, static means class level.
Are constructors always public?
No, Constructors can be public , private , protected or default (no access modifier at all). Making something private doesn’t mean nobody can access it. It just means that nobody outside the class can access it. Using private constructor we can ensure that no more than one object can be created at a time.
Why are constructors usually public?
The public constructor also means it can be accessible outside the class The other class can also getting them in a simply manner however if we make the constructor as private it is not accessible outside the class. Also we make constructor the constructor as public to initialized the class any where in the program .
What happens if I make a constructor private?
Private constructors are used to prevent creating instances of a class when there are no instance fields or methods, such as the Math class, or when a method is called to obtain an instance of a class. If all the methods in the class are static, consider making the complete class static.
Can a constructor be virtual?
Constructor can not be virtual, because when constructor of a class is executed there is no vtable in the memory, means no virtual pointer defined yet. Hence the constructor should always be non-virtual.
Can we use this () and super () in a method?
this() and super(), both are the constructors that’s why must be the first statement. But we can use both in a program. this(): It is used to call, same class Default or Parametrized Constructor. super(): It is used to call, immediate super/parent class Default or Parametrized Constructor.
Can abstract class have body?
Abstract methods cannot have body. Abstract class can have static fields and static method, like other classes. An abstract class cannot be declared as final.
Can we make abstract class as final?
Yes, there may be “final” methods in “abstract” class. But, any “abstract” method in the class can’t be declared final. It will give “illegal combination of modifiers: abstract and final” error.
Can abstract class be inherited?
An abstract class cannot be inherited by structures. It can contains constructors or destructors. It can implement functions with non-Abstract methods. It cannot support multiple inheritance.
Can we inherit static class?
Static classes are sealed and therefore cannot be inherited. They cannot inherit from any class except Object. Static classes cannot contain an instance constructor.
Which is better abstract class or interface?
The short answer: An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it. And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.
Can an interface implement an abstract class?
Interface contains only abstract methods that can’t be instantiated and it is declared by keyword interface. Now as all methods in an interface are abstract methods therefore we can implement it using Abstract Class.
Can we achieve 100% percent abstraction in an abstract class?
We can achieve 100% abstraction using interfaces. Abstract classes and Abstract methods : An abstract class is a class that is declared with abstract keyword. Any class that contains one or more abstract methods must also be declared with abstract keyword.
Are Interfaces 100% abstract?
Abstraction in interfaces The user who want to use the methods of the interface, he only knows the classes that implement this interface and their methods, information about the implementation is completely hidden from the user, thus achieving 100% abstraction.
What is abstraction with real time example?
Real Life Example of Abstraction in Java. Abstraction shows only important things to the user and hides the internal details, for example, when we ride a bike, we only know about how to ride bikes but can not know about how it work? And also we do not know the internal functionality of a bike.
Can we achieve 100% percent abstraction in an abstract class and if yes how if no why?
A class which is declared using abstract keyword known as abstract class. We cannot create object of abstract class. It is used to achieve abstraction but it does not provide 100% abstraction because it can have concrete methods. An abstract class must be declared with an abstract keyword.