Final Vs Finally Vs Finalize()



This is very important interview question. Lets get one by one.

Final

Final is a non access modifier that can be used with a variables, methods and also classes.

Final variables
    • Final variables cannot be changed, because they are constants. 
    • Look at the following code, it won't compile.

public class Fruits {

   public static void main(String[] args) {
       final int MAX_DIS = 5;
       MAX_DIS = 10;
  
       System.out.println(MAX_DIS);
   }
}


Final methods
    • Final methods cannot be overridden. 
    • Following code won't compile.

public class Fruits {
   final void eat() { }
}

class Apple extends Fruits {
   void eat() { }
}


Final classes
    • Final classes cannot be extended.
    • Following code won't compile.

public final class Fruits {

}

class Apple extends Fruits {

}


Finally

  • This is always associated with try-catch block.
  • It is normally used to handle any clean up codes like closing a file, closing a database to prevent resource leak.
  • This finally block runs every time either exception happen or not.
  • Look at the following example.

public class FinallyBlockDemo {

   public static void main(String args[]) {

       double num1=0, num2=0;
       Scanner scn = new Scanner(System.in);

       try{
           System.out.print("Enter number one: ");
           num1 = scn.nextInt();

           System.out.print("Enter number two: ");
           num2 = scn.nextInt();

           double div = num1 + num2;
           System.out.println("Answer is : " + div);
   
       }catch(InputMismatchException e){
            System.out.println("Please enter number only.");

       }finally{
            System.out.println("Service stopped.");

       }
   }
}


Finalize() 

  • This method is presented in Object class (Java.lang.Object.finalize())
  • This is called by the Garbage collector just before destroying any object.
  • If it determines any object without a reference, it calls this method anytime. 
  • This is used to perform clean up activities related to any object without reference.
  • This cleanup activities means, if the object is associated with any database connection, finalize() method is used to disconnect that connection. 





Final Vs Finally Vs Finalize() Final Vs Finally Vs Finalize() Reviewed by Ravi Yasas on 11:41 AM Rating: 5

1 comment:

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