Can We Declare Class As Final?

Can we execute a class without a main method?

Yes, we can execute a java program without a main method by using a static block.

Static block in Java is a group of statements that gets executed only once when the class is loaded into the memory by Java ClassLoader, It is also known as a static initialization block..

How do I make my class final?

To specify that your class is a final class, use the keyword final before the class keyword in your class declaration. For example, if you wanted to declare your (perfect) ChessAlgorithm class as final, its declaration would look like this: final class ChessAlgorithm { . . . }

When should you make a class final?

A final class is a class that can’t be extended. Also methods could be declared as final to indicate that cannot be overridden by subclasses. Preventing the class from being subclassed could be particularly useful if you write APIs or libraries and want to avoid being extended to alter base behaviour.

Can a constructor be final?

No, a constructor can’t be made final. A final method cannot be overridden by any subclasses. … But, in inheritance sub class inherits the members of a super class except constructors. In other words, constructors cannot be inherited in Java therefore, there is no need to write final before constructors.

What is difference between immutable and final?

final means that you can’t change the object’s reference to point to another reference or another object, but you can still mutate its state (using setter methods e.g). Whereas immutable means that the object’s actual value can’t be changed, but you can change its reference to another one.

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.

Which method Cannot be overridden?

A method declared final cannot be overridden. A method declared static cannot be overridden but can be re-declared. If a method cannot be inherited, then it cannot be overridden. A subclass within the same package as the instance’s superclass can override any superclass method that is not declared private or final.

What happens if a class is declared as final?

The main purpose of using a class being declared as final is to prevent the class from being subclassed. If a class is marked as final then no class can inherit any feature from the final class. You cannot extend a final class. If you try it gives you a compile time error.

Is String final in Java?

The string is immutable means that we cannot change the object itself, but we can change the reference to the object. The string is made final to not allow others to extend it and destroy its immutability.

Can we have 2 main methods in Java?

The answer is no; there can only one “main” method – where “main” means an entry point you can “run”. You can code overloaded versions as in your example, but they can’t be “run”. There can be more than one main method in a single program. But JVM will always calls String[] argument main() method.

Can we extend immutable class?

final class can’t be extended by other classes. If a class extend the class you want to make as immutable, it may change the state of the class due to inheritance principles. If you do not make it final I can extend it and make it non mutable.

Can you declare a class as private?

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

Why constructor is not overridden?

Constructor looks like method but it is not. It does not have a return type and its name is same as the class name. But, a constructor cannot be overridden. If you try to write a super class’s constructor in the sub class compiler treats it as a method and expects a return type and generates a compile time error.

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 we declare list as final?

4 Answers. You’re right that declaring the list final means that you cannot reassign the list variable to another object. … final as you know means that you cannot reassign the list variable another value.

Can we declare main method as final?

Yes, we can declare the main () method as final in Java. The compiler does not throw any error. If we declare any method as final by placing the final keyword then that method becomes the final method. The main use of the final method in Java is they are not overridden.

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. … We need to assign initial values for an instance variable we can use a constructor.

Can we break immutable class in Java?

More detailed answer: Yes serialization can break immutability. It looks great. It’s immutable (you can’t change start and end after initialization), elegant, small, threadsafe etc. You have to remember that serialization is another way of creating objects (and it is not using constructors).