Question: Can Constructor Be Static Or Final?

Is constructor by default final?

apply a final keyword to a method means you cannot override that method.

but by default in java no constructor can be overridden.

so there is no need to use final keyword with a constructor .

A constructor can’t inherited so can’t be overridden , so there is no use of making constructor final..

Can abstract class have constructor?

Yes! Abstract classes can have constructors! Yes, when we define a class to be an Abstract Class it cannot be instantiated but that does not mean an Abstract class cannot have a constructor. Each abstract class must have a concrete subclass which will implement the abstract methods of that abstract class.

Are constructors inherited?

A subclass inherits all the members (fields, methods, and nested classes) from its superclass. Constructors are not members, so they are not inherited by subclasses, but the constructor of the superclass can be invoked from the subclass.

What is difference between final and static?

static means there is only one copy of the variable in memory shared by all instances of the class. The final keyword just means the value can’t be changed. Without final , any object can change the value of the variable.

Why is main method static?

Why the main () method in Java is always static? Java main() method is always static, so that compiler can call it without the creation of an object or before the creation of an object of the class. In any Java program, the main() method is the starting point from where compiler starts program execution.

Can a constructor be virtual?

In C++, the constructor cannot be virtual, because when a constructor of a class is executed there is no virtual table in the memory, means no virtual pointer defined yet. So, the constructor should always be non-virtual. But virtual destructor is possible.

Can constructor be final or static in Java?

No Constructors can NEVER be declared as final. Your compiler will always give an error of the type “modifier final not allowed” Final, when applied to methods, means that the method cannot be overridden in a subclass. Constructors are NOT ordinary methods.

Can abstract method have body?

Abstract methods means there is no default implementation for it and an implementing class will provide the details. So, it’s exactly as the error states: your abstract method can not have a body. The reason you would do something like this is if multiple objects can share some behavior, but not all behavior.

Can constructors and destructors be inherited?

If you don’t explicitly invoke a specific superclass constructor, then the default superclass constructor will be called (assuming it’s visible). Destructors are not inherited. If a class doesn’t define one, the compiler generates one.

Can we overload the constructors?

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 constructor be static?

A static constructor does not take access modifiers or have parameters. A class or struct can only have one static constructor. Static constructors cannot be inherited or overloaded. A static constructor cannot be called directly and is only meant to be called by the common language runtime (CLR).

Can private constructor class inherited?

If class with private constructor and sealed class cannot be inherited , then what is the use of class which cannot be inherited. … And as said previously private constructor can be excused as we have static classes now. So private constructor + sealed means pure static class. Also sealed class cannot be inherited.

Can a constructor be final?

No, a constructor can’t be made final. A final method cannot be overridden by any subclasses. … In other words, constructors cannot be inherited in Java therefore, there is no need to write final before constructors.

Can a constructor be private?

Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.

Can a constructor be abstract?

You can’t have an abstract constructor, as abstract means you need to provide the implementation for that at some point of time in your subclass. But you cannot override constructor. There will be no point in having an abstract constructor : Since the constructor needs to be of the same name as of class.

Why constructor is not overridden?

Constructor Overriding is never possible in Java. This is because, Constructor looks like a method but name should be as class name and no return value. Overriding means what we have declared in Super class, that exactly we have to declare in Sub class it is called Overriding.

Can we declare an interface as final?

If you make an interface final, you cannot implement its methods which defies the very purpose of the interfaces. Therefore, you cannot make an interface final in Java. Still if you try to do so, a compile time exception is generated saying “illegal combination of modifiers − interface and final”.

Can static methods be final?

Static methods belong to the class, not the instance. … Static methods with the same signature from the parent class are hidden when called from an instance of the subclass. However, you can’t override/hide final methods. You would think the error message would use the word hidden instead of overridden…

Can you use this () and super () both in a constructor?

Both this() and super() are constructor calls. Constructor call must always be the first statement. So you either have super() or this() as first statement. Both this() and super() are constructor calls, and constructor call must be the first (and only first) call in a constructor.

Can a data field be declared abstract?

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.

Can abstract class have body?

Abstract methods are declaration only and it will not have implementation. It will not have a method body. A Java class containing an abstract class must be declared as abstract class. An abstract method can only set a visibility modifier, one of public or protected.

Why we Cannot override static method?

Static methods cannot be overridden because they are not dispatched on the object instance at runtime. The compiler decides which method gets called. Static methods can be overloaded (meaning that you can have the same method name for several methods as long as they have different parameter types).

Can final method be overloaded?

private and final methods can be overloaded but they cannot be overridden. It means a class can have more than one private/final methods of same name but a child class cannot override the private/final methods of their base class.

Is constructor return any value?

No, constructor does not return any value. While declaring a constructor you will not have anything like return type. In general, Constructor is implicitly called at the time of instantiation.

Can constructor throw exception?

Yes, constructors are allowed to throw an exception in Java. A Constructor is a special type of a method that is used to initialize the object and it is used to create an object of a class using the new keyword, where an object is also known as an Instance of a class.

Should constructors be private or 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.

When should a constructor be 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.