Why do we use protected keyword in Java?

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Elements declared as private are only accessible in the class in which they are declared, while protected keywords allow access from subclasses and members of the same package.

What does Protected mean Java?

In Java, protected means that members can be accessed in any class of the same package or in subclasses even if they belong to another package. Note Protected variables are not visible outside the package. For example, B extends A and A has a protected int x It can be used in class B.

Where we can use protected in Java?

Protected access modifier – protected Variables, methods, and constructors declared as protected in a superclass can only be accessed by subclasses of other packages or by any class in a package of protected member classes. The protected access modifier cannot be applied to classes and interfaces.

What is the use of protected variable?

Protected variables are data members of a class and classes derived from that class that can be accessed within the class. In Python, there are no “public” instance variables. However, the underscore ‘_’ symbol is used to determine access control for data members within a class.

What is protected keyword?

The protected keyword is a member access modifier. This page describes protected access. The protected keyword is also part of the protected internal and private protected access modifiers. Protected members can be accessed from within their class and from derived class instances.

What is difference between protected and default in Java?

For Java Testers Protected access specifiers appear in the same package and in subclasses, while Default is a package-level access specifier and can appear in the same package.

Can we declare class as protected?

No, a top-level class cannot be declared private or protected. It can be either public or default (no qualifier).

Why we Cannot declare class as protected?

class is defined protected —> Cannot be extended (not visible) from outside the package. Also, if it cannot be extended, it makes no sense to leave it protected. This is because it will be the default access allowed.

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What is protected vs private?

private: The type or member can only be accessed by code of the same class or structure. protected: The type or member can only be accessed by code in the same class or in a class derived from that class.

Can protected methods be overridden?

Yes, protected methods of a superclass can be overridden by subclasses. If a superclass method is protected, the overridden method of the subclass can be protected or public (but not default or private). This means that overridden methods of subclasses cannot have weak access specifiers.

How do you call a protected method in Java?

Example 2

  1. class A
  2. protected String msg=”Try to access an out-of-class protected variable in a package”;
  3. >
  4. public class ProtectedExample2
  5. public static void main(String[] args)
  6. A a=New A();
  7. System.out.println(a.msg);
  8. >

Can we have protected constructor in Java?

The public, protected, and private modifiers can be used in the constructor. Private constructors can be used in Java when creating singleton classes.

What is polymorphism in Java?

In Java, polymorphism refers to the ability of a class to provide different implementations of a method, depending on the type of object being passed to the method. Simply put, polymorphism in Java allows the same action to be performed in different ways.

What is the difference between protected and public?

The difference between public and protected is that public can be accessed from outside the class, while protected cannot.

Can a class be static in Java?

Classes can be static, which most developers are aware of. Thus, some classes can be made static in Java. Java supports static instance variables, static methods, static blocks, and static classes. Classes in which nested classes are defined are called external classes.

What is immutable class in Java?

Immutable classes in Java mean that once an object is created, its contents cannot be modified. In Java, all wrapper classes (Integer, Boolean, Byte, Short, etc.) and String classes are immutable.

Can we extend private class?

No, you cannot override private or static methods in Java. Private methods in Java are invisible to other classes whose scope is limited to the class in which they are declared.

Can we declare abstract method as private?

If a class method is private, it cannot be accessed outside the current class, not from the child class. However, if the method is abstract, it cannot be used from the same class. It must be used and used from a subclass. Therefore, abstract methods cannot be private.

What if a class is private?

Private classes are allowed, but only as inner or nested classes. If there is a private inner or nested class, access is restricted to the scope of that outer class. If you have your own private class as a top-level class, you cannot access it from anywhere.

What is a static class?

Static classes are essentially the same as non-static classes, with one difference. You cannot instantiate a static class. That is, you cannot use new operators to create variables of the class type.

Which is the wrapper class in Java?

A wrapper class is a class that contains primitive data types (int, char, short, byte, etc.). In other words, wrapper classes provide a way to use primitive data types (int, char, short, byte, etc.) as objects. These wrapper classes are under the Java UTIL package.

What are types of polymorphism?

Polymorphic Types

  • Subtype Polymorphism (runtime) Subtype polymorphism is the most common type of polymorphism.
  • Parametric polymorphism (overload)
  • Ad hoc polymorphism (compile time)
  • Forced polymorphism (casting)

Is protected better than private?

Only member or friend functions have access to private data members of a class. Class members declared as protected cannot be accessed outside the class, but can be accessed by any subclass (derived class) of that class. Private members are not inherited by the class.

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What is inheritance in OOP?

OOP = class is derived from another class. A child class inherits all public and protected properties and methods from its parent class. Additionally, it can have its own properties and methods. Inherited classes are defined using the extends keyword.

Can we overload static method in Java?

Can I override static methods? No, you cannot override a static method because method overrides are based on runtime dynamic binding and static methods are bound using static binding at compile time. Therefore, static methods cannot be overridden.

Is protected methods are final?

1) Private methods are final. 2) Protected members are accessible within the package and can access inherited classes outside the package. 3) Protected methods are final.

Can we call protected method using object?

No, an object type (class) cannot be converted to another object type at runtime. It can be wrapped into another object, but the protected access problem still remains.

Can constructor be static?

Java Constructors Are Not Static One important property of Java constructors is that they cannot be static. The static keyword indicates that the object belongs to a class, not an object of the class. The static constructor is not used because the constructor is invoked when an object of the class is created.

Can we use void with constructor?

Note that the constructor name must match the class name, and it does not have a return type (e.g., void). Also note that the constructor is called when the object is created.

Can we override private method in Java?

You cannot override private or static Java methods. Creating a similar method in a child class with the same return type and the same method arguments will hide the superclass method. This is called method hiding. Similarly, you cannot override a private method in a subclass.

What is the difference between a constructor and a method?

Constructors are used to create and initialize objects. Methods are used to execute specific statements. Constructors are called implicitly by the system. Methods are called during program code.

What is overloading in Java?

Overloading in Java is the ability to define multiple methods with the same name in a class. The compiler can distinguish between methods for method signatures.

What is multithreading in Java?

In Java, multithreading refers to a process that runs two or more threads simultaneously to maximize CPU utilization. Threads in Java are lightweight processes that require fewer resources to create and share process resources.

What is subclass in Java?

In the Java language, classes are derived from other classes and can inherit fields and methods from those classes. Definition: A class derived from another class is called a subclass (derived class, extended class, or child class).

Can we change static variable?

Static methods cannot access or modify instance variables or the value of this reference (since there is no calling object). Static methods cannot call non-static methods.

Can we use static in abstract method?

If you want to use a method in a class summary, you must override this method in a subclass. However, overriding a static method is not possible. Therefore, abstract methods cannot be static.

What is a singleton in Java?

In Java, singleton is a design pattern that guarantees that a class can have only one object. To create a Singleton class, the class must implement the following properties Create a private constructor for the class to restrict its creation.

Can we declare main class as static?

Thus, yes, a class can be declared Class Static in Java if it is within a top-level class. Such a clause, also known as a nested class, can be declared static, but is not allowed if you are considering making the top-level class static in Java.

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Is Double immutable in Java?

For example, Java, String, Integer, and Double are immutable classes, while StringBuilder, Stack, and Java Array are variable.

Why wrapper classes are immutable in Java?

This is because all primitive wrapper classes (Integer, Byte, Long, Float, Double, Character, Boolean, and Short) are immutable in Java, so operations such as addition and subtraction create new objects and do not modify old ones.

Why constructor is private in Singleton?

Singleton classes use private constructors to prevent the target class from instantiating the class directly by calling the constructor, but the objects of the singleton class can be instantiated by calling a static method whose logic provides only one provided to the target class. The object of the singleton class is written / …

Can abstract class have constructor?

As with other classes in Java, an abstract class can have a constructor even if it is called only from a concrete subclass.

Can return type change in overriding?

Beginning with Java 5, a method can be overridden by changing the return type only by adhering to the condition that the return type is a subclass of the overridden method return type.

Can abstract method be overridden?

Subclasses must override all abstract methods of the abstract class. However, it is not required to override abstract methods if the subclass is declared as abstract.

Can we use abstract keyword with constructor?

Since the constructor cannot be overridden, it cannot provide a body when abstracted. Therefore, the abstract keyword cannot be used in the constructor.

Can we declare local inner class as abstract?

Local inner classes are not members of the enclosed class. They belong to internally defined blocks because they cannot have access modifiers associated with local inner classes. However, they can be marked as final or abstract.

Can an abstract class be static?

Yes, there is a static way for abstract classes. The reason for this is that static methods do not work on instances of the class, they are directly associated with the class itself.

Can we have constructor in interface?

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

What is final class in Java?

The final modifier to terminate the implementation of classes, methods, and variables. The main purpose of using a class declared as final is to prevent the class from being subclassed. If a class is marked as final, no class can inherit functionality from the final class. The final class cannot be extended.

What is abstract method in Java?

Abstract class: A restricted class that cannot be used to create objects (it must inherit from another class to be accessible). Abstract methods: Can only be used in abstract classes and have no body. The body is provided by a subclass (the inheritor).

Why is outer class not static in Java?

The static keyword is intended to provide memory and execute logic without creating objects, so it is not possible to declare an external (top-level) class as static. The static keyword cannot be used for external classes because classes do not directly contain value logic.

Why main method is static in Java?

An object of the class does not exist at the start of the Java runtime. Therefore, the main method must be static so that the JVM can load the class into memory and call the main method. If the main method is not static, the JVM cannot call it because the object of the class does not exist.