No, a top-level class cannot be made private or protected. It may be default or public (no modifier). It is expected to have a default access if it lacks a modifier.
Why we Cannot declare class as protected in Java?
Class is defined as protected, so it cannot be extended from a package outside of its own (not visible). And since it will then become the default access, which is permitted, if it cannot be extended, maintaining it as protected is pointless.
Can a class be declared with a protected modifier?
The protected access modifier can be accessed both inside and outside of a package, but only via inheritance. The constructor, method, and data member are all compatible with the protected access modifier. It isn’t applicable in class.
How do you define a protected class in Java?
Modifier for Protected Access – Protected
Only the subclasses in the other package or any class within the package of the protected members’ class may access variables, methods, and constructors that have been declared protected in a superclass. Class and interfaces are exempt from the protected access modifier.
Can we declare class as protected in C#?
Accessibility of class, record, and struct members
Any of the six types of access can be declared for class and record members, including those in nested classes, records, and structs. Because structs don’t support inheritance, they cannot be declared as protected, protected internal, or private protected.
Can constructor be private?
Yes, we are allowed to make a constructor private. We are unable to create an object of a class if we declare a constructor as private. This private constructor can be utilized with the Singleton Design Pattern.
Can we declare static methods as private?
In Java 9, it is possible to include private methods or private static methods in an interface.
Can constructor be protected in Java?
Allowing access specifiers and modifiers with constructors
Constructors may use public, protected, and private modifiers. When building a singleton class in Java, we can use a private constructor. The Singleton’s function is to regulate object creation and enforce a one-object maximum.
Why protected modifier is used?
The protected modifier designates that the member can only be accessed by a subclass of its class in another package as well as within its own package (like with package-private). The access to members that each modifier permits is displayed in the following table.
Can protected methods be overridden?
Yes, a subclass may override a superclass’s protected method. The subclass overridden method cannot have a weaker access specifier if the superclass method is protected. Instead, it can have protected or public access (but not default or private).
Can a class be public/private protected and default?
Everything that is public is accessible to anyone, everything that is private is only accessible within the class in which it was declared, everything that is protected is accessible outside the package, but only to child classes, and everything that is default is accessible only inside the package.
Can a class be static in C#?
A static class may be created in C# by using the static keyword. Only static constructors, static methods, and static data members are permitted in static classes. The creation of static class objects is prohibited. You cannot inherit a static class from another class because static classes are sealed.
What is sealed class in C#?
In C#, a sealed class is one that can be instantiated but cannot be inherited by any other classes. The purpose of a sealed class is to show that the class is specialized and that no additional functionality needs to be added to it via inheritance in order to override its behavior.
Can constructor be static or final?
Java constructors aren’t allowed to be static
The fact that a Java constructor cannot be static is one of its key characteristics. We are aware that the static keyword refers to a class rather than a class object. There is no use of the static constructor because a constructor is called whenever an object of a class is created.
What is a singleton in Java?
A design pattern called Singleton in Java makes sure that a class can only contain one object. A class must implement the following characteristics in order to be a singleton class: To prevent objects from being created outside of the class, add a private constructor to the class.
Can abstract method be overridden?
All abstract methods of an abstract class must be overridden by a subclass. It’s not necessary to override abstract methods if the subclass is declared abstract, though.
Can abstract class can have constructor?
Even though they are only called from their concrete subclasses, abstract classes in Java are still able to have constructors.
Can a class be static in Java?
Since most developers are aware that classes can be static, some classes in Java can be made static. Java supports static classes, static blocks, static methods, and static instance variables. The Outer Class is the class in which the nested class is defined.
What are static classes?
The main distinction between a static class and a non-static class is that a static class cannot be instantiated. In other words, you are unable to create a variable of the class type using the new operator.
Can we use void with constructor?
Keep in mind that the constructor cannot have a return type and that its name must correspond to the class name (like void ). Also take note that when an object is created, the constructor is called.
Is static a keyword in Java?
The static keyword in Java is primarily utilized for memory management. Variables, methods, blocks, and nested classes can all be used with it. It is a keyword used to share a variable or method across different classes. Static is primarily used for variables or methods that are constant across all instances of a class.
What is Polymorphism in Java?
Polymorphism in Java refers to a class’s capacity to offer various implementations of a method depending on the kind of object it receives as a parameter. Simply put, polymorphism in Java enables us to carry out the same action in a variety of ways.
Is private method are final?
In order to respond to question 2, I would say that all compilers will treat private methods as final. Any overriding of a private method is forbidden by the compiler. Additionally, no compiler will allow subclasses to override final methods.
Can abstract be synchronized?
Java does not support synchronization of abstract methods. When a method is synchronized, it implies that the method’s code is also synchronized, meaning that only the thread that is currently accessing the method’s code is permitted to do so.
Can constructor be synchronized in Java?
Keep in mind that constructors cannot be synchronized; it is improper to use the synchronized keyword with a constructor. Because only the thread that creates an object should have access to it while it is being constructed, synchronizing constructors is illogical.
Can interface be protected in Java?
The protected members can typically be accessed within the same class or a class that inherits it. However, we will implement the interface; we do not inherit it. As a result, an interface’s members cannot be protected.
Can we inherit static method in Java?
Instance variables of any objects belonging to the class in which a static method is defined are not used. Static methods do not make use of variables; instead, they compute something from all the data in the parameters. Java allows us to inherit static methods.
What are types of polymorphism?
Types of Polymorphism
- Subtype heterogeneity (Runtime) The most prevalent type of polymorphism is subtype polymorphism.
- Statistical polymorphism (Overloading)
- Polymorphism ad hoc (Compile-time)
- polymorphism under coercion (Casting)
What is the difference between public/private and protected?
In general, public means that anyone can access, private means that only people who belong to the same class can access, and protected means that people who belong to subclasses can also access.
Why namespace is used in C sharp?
In C#, namespaces are used to group and separate codes to a certain extent. You can think of them as a container for other namespaces, classes, etc. The following types can be members of a namespace: Namespaces (Nested Namespace) (Nested Namespace)
Why do we use namespace in C?
Declaring a scope that contains a collection of connected objects uses the namespace keyword. A namespace can be used to group coding components and develop types that are universally unique.
What is polymorphism in C#?
Polymorphism, which is defined as having “many forms” happens when there are numerous classes that are related to one another through inheritance. We can inherit fields and methods from another class through inheritance, as we mentioned in the previous chapter. These techniques are used by polymorphism to carry out various tasks.
Why multiple inheritance is not possible in C#?
Multiple inheritance is not supported by the C# compiler by design because it leads to method ambiguity from various base classes. This is due to issues with two different classes of diamond shapes. If classes A and B both inherit from class A, and classes B and C both inherit from class D.
Can we inherit abstract class?
Structures cannot inherit from an abstract class. It might include constructors or destroyers. It can use non-Abstract methods to implement functions. There can be only one inheritance supported.
Is abstract class sealed?
A class cannot be inherited if it is declared sealed, and abstract classes cannot be sealed.
Can a constructor be private in C++?
Constructors typically have public accessibility so that programs outside of the definition of the class or its inheritance hierarchy can produce objects of that class. However, a constructor can also be marked as protected or private.
What is a private constructor?
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.
Can we override constructor?
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. A constructor, however, cannot be replaced. The compiler treats it as a method, expects a return type, and produces a compile time error if you attempt to write a constructor for a super class in a sub class.
Can we declare interface as final?
interface methods cannot be considered final. Cannot be deemed conclusive.
Is enum thread safe?
Enum instance creation is thread-safe
The Enum instance is thread-safe by default, so you don’t have to be concerned about double-checked locking. In conclusion, given the guaranteed serialization and thread-safety, and with a few lines of code enum, the Singleton pattern is the best way to create Singletons in the Java 5 world.
Can we create immutable class in Java?
In Java, an immutable class means that once an object is created, its content cannot be changed. All wrapper classes in Java, such as Integer, Boolean, Byte, and Short, as well as the String class, are immutable. We can also design our own immutable class.
Can abstract method be static?
If you want to use a method that is declared abstract in a class, you must override it in the subclass. However, with static methods, overriding is not an option. An abstract method cannot be static as a result.
Can final methods be abstract?
A final abstract combination is therefore prohibited for classes. As a result, an abstract class can contain a final method but an actual class cannot.
Can we use super keyword in abstract class?
Because AbstractClass. m() has been declared abstract and has no suitable implementation on the parent of the inner class, the super keyword is ineffective in this situation. Keep in mind that inner classes only include a reference to the outer class rather than extending it (even if the two classes are of the same type).
Can interface be overridden?
Interface methods can be used, so no. It is necessary to define the method before overloading or overriding it.
Can we instantiate abstract class?
Although they cannot be created from scratch, abstract classes can be subclassed. When a subclass of an abstract class is created, it typically offers implementations for each of the parent class’s abstract methods. The subclass must also be declared abstract if it doesn’t, though.
Why constructor is not used in interface?
Builder in an interface
Because all data members in interfaces are public static final by default and are constants, an interface in Java does not have a constructor (assign the values at the time of declaration). An interface lacks data members that can be initialized in the constructor.
Can we have static outer class?
Java doesn’t support outer static classes. since the static modifier would not change the visibility of any outer classes, which is the case. However, you can easily make all of the class’s methods and variables static if you mean that you don’t need an instance of the class.
Can you extend a private class?
Yes, it most definitely can! That does not imply that it must. When used properly, Java’s extension feature is a nice feature.
Can inner class create static?
Only nested classes are permitted to be static in Java. The outer class is connected to static nested classes. We don’t require any objects of the outer class in order to access the static nested class.
What is a final class in Java?
The last modifier to complete the classes, methods, and variable implementations. The main goal of using a class that has been marked as final is to prevent subclassing. No class can inherit any features from a class that has been declared final. A final class cannot be extended.
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.
How many constructor can a class have?
A class may contain up to 65535 constructors (According to Oracle docs).