In Java, the final keyword is used as defining something as constant /final and represents the non-access modifier.
When a variable is declared as final in Java, the value can’t be modified once it has been assigned.
If any value has not been assigned to that variable, then it can be assigned only by the constructor of the class.
A method declared as final cannot be overridden by its children's classes.
A constructor cannot be marked as final because whenever a class is inherited, the constructors are not inherited. Hence, marking it final doesn't make sense. Java throws compilation error saying - modifier final not allowed here
No classes can be inherited from the class declared as final. But that final class can extend other classes for its usage.