Can we declare class as protected in C#?

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Note that you cannot declare any outer class as private, protected (or protected internal) in c# since the access modifier for outer level classes defines their visibility in relation to other assemblies.

Can a class be declared as protected?

No, we cannot declare a top-level class as private or protected. It can be either public or default (no modifier).

Why we Cannot declare class as protected?

class is defined protected —> it cannot be extended from outside package(not visible). And if it cannot be extended then it is meaningless to keep it as protected, because then it will become default access which is allowed.

When should I use protected in C#?

C# protected is used to allow derived classes access to base class properties and methods with the same name as long as those properties and methods are not private. As with other access modifiers, protected can be used with fields, properties and methods.

Can we inherit private class in C#?

Yes, The are inherited. But you cannot access them as they are private :).

Can a protected class be inherited in C#?

A protected class could not be defined inside a namespace.It could only be declared as a nested class. It could be instantiated inside other nested classes and could be inherited by other nested classes and It can inherit from other nested classes.

Can we declare abstract method as private?

If a method of a class is private, you cannot access it outside the current class, not even from the child classes of it. But, incase of an abstract method, you cannot use it from the same class, you need to override it from subclass and use. Therefore, the abstract method cannot be private.

Can we declare abstract class as final?

Abstract classes are similar to interfaces. You cannot instantiate them, and they may contain a mix of methods declared with or without an implementation. However, with abstract classes, you can declare fields that are not static and final, and define public, protected, and private concrete methods.

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What is sealed class in C#?

A sealed class, in C#, is a class that cannot be inherited by any class but can be instantiated. The design intent of a sealed class is to indicate that the class is specialized and there is no need to extend it to provide any additional functionality through inheritance to override its behavior.

What is polymorphism in C#?

Polymorphism means “many forms”, and it occurs when we have many classes that are related to each other by inheritance. Like we specified in the previous chapter; Inheritance lets us inherit fields and methods from another class. Polymorphism uses those methods to perform different tasks.

Why Multiple inheritance is not possible in C#?

C# compiler is designed not to support multiple inheritence because it causes ambiguity of methods from different base class. This is Cause by diamond Shape problems of two classes If two classes B and C inherit from A, and class D inherits from both B and C.

Can we declare private class in namespace?

No, Allowing classes to be private to a namespace would achieve no meaningful level of protection. Because private means that the member is only access in the containing class. Since a top-level class has no class containing it; it cannot be private or protected.

Can destructor be private?

Destructors with the access modifier as private are known as Private Destructors. Whenever we want to prevent the destruction of an object, we can make the destructor private.

Can constructor be static?

Java constructor can not be static

One of the important property of java constructor is that it can not be static. We know static keyword belongs to a class rather than the object of a class. A constructor is called when an object of a class is created, so no use of the static constructor.

Can we override static method?

No, we cannot override static methods because method overriding is based on dynamic binding at runtime and the static methods are bonded using static binding at compile time. So, we cannot override static methods. The calling of method depends upon the type of object that calls the static method.

Can we use static in abstract class?

Yes, of course you can define the static method in abstract class. you can call that static method by using abstract class,or by using child class who extends the abstract class. Also you can able to call static method through child class instance/object.

Can we have constructor in interface?

No, you cannot have a constructor within an interface in Java. You can have only public, static, final variables and, public, abstract, methods as of Java7.

Can I declare local variable as static?

A static variable in Java is a class variable (for whole class). Therefore, it defeats the point of static to have a local variable that is static (a variable whose scope is restricted to function). Compilers therefore forbid the use of static local variables.

What is inheritance in C#?

The ability to define derived classes that either inherit or override a base class’s specific functionality (data and behavior) is a feature of object-oriented programming languages known as inheritance.

What is static keyword in C#?

The word “static” denotes that a member of a class only exists in a single instance. Since their values can be retrieved by calling the class without creating an instance of it, static variables are used to define constants.

Can we inherit Singleton class in C#?

A static class cannot be instantiated or inherited. Singleton classes, in contrast to static classes, can inherit, have a base class, be serialized, and implement interfaces. You can use Singleton classes to implement the Dispose method. Therefore, static classes are significantly less adaptable than Singleton classes.

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What is difference between static and sealed class in C#?

When the program or namespace containing the class is loaded, the. NET Framework common language runtime (CLR) automatically loads static classes. It is not possible to use a sealed class as a base class. The main purpose of sealed classes is to avoid derivation.

Is method overloading a polymorphism?

A polymorphism created at compile time is method overloading.

Can a namespace have more than one class?

In a single program, two classes with the same name can be created in two different namespaces. No two classes may share the same name within a namespace.

Why do we need abstract classes?

The quick response is that you can design functionality that subclasses can implement or override using abstract classes. You cannot actually implement functionality; only define it using an interface. Additionally, a class can utilize numerous interfaces as opposed to only being able to extend one abstract class.

Can we inherit multiple abstract classes in C#?

Multiple inheritance is not supported by abstract classes.

What is private constructor in C#?

A unique instance constructor is a private constructor. It is typically applied to classes with only static members. Other classes (aside from nested classes) cannot create instances of a class if it has one or more private constructors but no public constructors. For instance: C# Copy.

What is a constructor C#?

When an object of a class is created, C# constructors are special methods that are automatically called to initialize all of the class data members. The compiler automatically creates a default constructor if there aren’t any explicitly defined constructors in the class.

Can we change static variable?

Since there is no calling object for instance variables or this reference, static methods are unable to access or modify their values, and they are also unable to call non-static methods.

Can member function private?

C++’s private member function

These operations can be added to the private section. Only functions that belong to the same class as the private member function may call it. The dot operator cannot even be used to call a private function from an object.

Can a virtual function be called from constructor?

A virtual function may be called in a constructor, but exercise caution. It might not perform as expected. The virtual call mechanism in a constructor is disabled because overriding from derived classes hasn’t happened yet. The phrase “base before derived” refers to the way that objects are built.

Can we have virtual destructor?

You can have a pure virtual destructor, yes. Pure virtual destructors are acceptable in standard C++, and one of the most crucial things to keep in mind is that a class must provide a function body for any pure virtual destructor it contains.

Can constructor have return type?

No, Java doesn’t have a return type for constructors. Constructor appears to be a method but is not one. Its name is the same as the class name and it lacks a return type. In most cases, it is used to initialize a class’ instance variables.

Can we overload the constructor?

Similar to function overloading, constructor overloading is a possibility. The class name is the same for overloaded constructors, but they take a different number of arguments. The appropriate constructor is called based on the quantity and kind of arguments passed.

Can we declare abstract constructor?

In an abstract class, a parameterized constructor can be defined.

Can main method be abstract?

The main() method can be used in abstract classes, yes. Since the main() method is static, it belongs to the class rather than an object or instance. There is no issue if the abstract contains the main method because it applies to the object.

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Can we overload final method?

Can a Final Method be Overridden? No, it is not possible to override or hide methods that have been declared final. Because of this, a method should only be declared final when we are certain that it is finished.

Can return type change in overriding?

Since Java 5, we can only override a method by changing its return type if it complies with the requirement that the overridden method’s return type is a subclass of the original method’s return type.

Can abstract method be private?

A class method that is private prevents access from outside the current class, including from its child classes. However, if a method is abstract, you must override it in a subclass before using it from the same class. The abstract method cannot be private as a result.

Can we declare abstract class as final?

Interfaces and abstract classes are similar. They can contain a mixture of methods declared with or without an implementation, and you cannot instantiate them. However, you can declare fields that are not static and final as well as define public, protected, and private concrete methods when using abstract classes.

Why main method is static?

Java’s main() method is static by default, allowing the compiler to call it either before or after creating a class object. The main() method is where the compiler begins program execution in every Java program.

What is difference between Singleton and static class in C#?

A singleton can implement interfaces, allow inheritance, and derive from other classes. While a static class is unable to inherit the members of an instance. Singletons can therefore maintain state and are more adaptable than static classes. A Singleton can be loaded automatically by the and initialized lazily or asynchronously.

Why abstract class has a constructor?

The initialization of a newly created object is the constructor’s primary function. There is an instance variable, abstract methods, and non-abstract methods in an abstract class. Abstract classes have a constructor because we need to initialize the non-abstract methods and instance variables.

Can we use constructor in inheritance?

Constructors in Java cannot be inherited. With the exception of constructors, a subclass inherits the members of a superclass. In other words, since constructors in Java cannot be inherited, final is not required before constructors.

What is difference between global and static variable?

A static variable only has a block scope, whereas a global variable can be accessed from anywhere within the program. Therefore, the advantage of using a static variable as a global variable is that since it is declared globally, it can be accessed from anywhere within the program.

Can we use static in place of global?

Declare a global variable static if you want it to be accessible from only one.c file. It is not advisable to declare a global variable static if it will be used in multiple.c files.

What is void in C#?

To indicate that a method (or local function) doesn’t return a value, you can use the return type void. C# Copy.

Is void return type?

In many programming languages descended from C and Algol68, the void type is the return type of a function that returns normally but does not give its caller a result value. Typically, these functions are used for the side effects they produce, like carrying out a task or writing to their output parameters.

What is abstraction in C#?

Classes and Methods in Abstract

Data abstraction is the process of withholding some information from the user and only displaying what is absolutely necessary. Abstract classes or interfaces can be used to achieve abstraction (which you will learn more about in the next chapter).