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Core Java - Interview Questions and Answers for 'Final' - 51 question(s) found - Order By Newest

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture.
  Q1. What is the difference between final, finally and finalize() ?Core Java
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Ans. final - constant variable, objects cannot be de-referenced, restricting method overriding, restricting class sub classing.

finally - handles exception. The finally block is optional and provides a mechanism to clean up regardless of what happens within the try block. Use the finally block to close files or to release other system resources like database connections, statements etc.

finalize() - method helps in garbage collection. A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state.

  Sample Code for final

  Sample Code for finally

  Sample Code for finalize

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Not frequently asked as it was introduced with Java 8.
 Q2. Difference between final and effectively final ? Why is effectively final even required ?Core Java
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Ans. Final variable means a variable that has been declared final and hence cannot be de referenced after initialization. Effective final means a variable that has not been declared final but haven't been reassigned the value after initialization.

First is the regulation that restricts the reassignment and will raise a compilation error if we try to do so. Second is the outcome without the restriction.

Effective Final is the eventual treatment of the variable that is required for many features. For eq - Java 8 requires that local variables referenced from a lambda expression must be final or effectively final.It means all local referenced from lambda expressions must be such that their value shouldn't be changed after initialization whether declared final or not.

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q3. What is a final method ?Core Java
Anonymous
Ans. Its a method which cannot be overridden. Compiler throws an error if we try to override a method which has been declared final in the parent class.

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q4. What is a Final Variable ?Core Java
Anonymous
Ans. Final variable is a variable constant that cannot be changed after initialization.

  Sample Code for final variable

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 Q5. Can we override compareTo method for Enumerations ?Core Java
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Ans. No. compareTo method is declared final for the Enumerations and hence cannot be overriden. This has been intentionally done so that one cannot temper with the sorting order on the Enumeration which is the order in which Enum constants are declared.

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 Q6. When we say final x = 10, is the reference final or the value ?Core Java2017-07-29 13:27:04

Ans. final keyword have meaning only to referenced and not the value. It means that the specified reference cannot be dereferenced. It doesn't control the value assigned to the memory that's being referenced. This is the reason that final object references doesn't mean that the object is immutable but means that the reference cannot be changed to point to new object.

In case of primitive types too, when we assign a reference to another, values are passed and not the object reference, and hence a new placeholder is created in memory with the same value. That is why final to that context means that you cannot change the assigned memory and there is no way we can have that memory place have another value.

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 Q7. What is a Final Method ?Core Java
Anonymous
Ans. A Method that cannot be overriden in the sub class.

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Very Frequently asked.Favorite question in Walk in drive for many Indian service companies.
 Q8. What is a Final Class ?
Anonymous
Ans. A Class that cannot be sub classed.

  Sample Code for final class

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 Q9. Does Declaring an object "final" makes it immutable ?Core Java
Anonymous
Ans. Only declaring variables as final makes them immutable. Making objects final means that the object handler cannot be used to target some other object but the object is still mutable.

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 Q10. How can we make sure that a code segment gets executed even in case of uncatched exceptions ?
Anonymous
Ans. By putting it within finally.

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 Q11. Should we override finalize method ?
Anonymous
Ans. Finalize is used by Java for Garbage collection. It should not be done as we should leave the Garbage Collection to Java itself.

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 Q12. Is it necessary that each try block to be followed by catch block ? Core Java
Anonymous
Ans. It should be followed by either catch or finally block.

  Sample Code for Retry in case of exception

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 Q13. Can we have try and catch blocks within finally ?Core Java
Admin
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Ans. Yes

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Frequently asked.
 Q14. When does the finally block gets executed ?Core Java2016-10-31 09:29:10

Ans. A finally block of code always executes, whether or not an exception has occurred.The only time finally won't be called is if you call System.exit() or if the JVM crashes first.

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 Q15. Does use of Final class enforces composition over Inheritance in Java ? Core Java2018-07-16 06:49:53

Ans. Yes, to a certain extent. But the objective for Final class could be beyond just enforcing composition as certain classes might have been created without inheritance or composition in mind.

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 Q16. What could be the reasons for restricting inheritance using final class ?Core Java2018-07-16 06:52:00

Ans. 1. Enforcing composition over inheritance
2. Restricting overriding of certain methods
3. Final methods are faster than regular instance methods
4. Enforcing Immutability

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 Q17. What is a finalize method ?Core Java
Anonymous
Ans. finalize() method is called just before an object is destroyed.

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 Q18. Can finally block be used without catch ?Core Java
Anonymous
Ans. Yes but should follow "try" block then.

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 Q19. How finally used under Exception Handling?Core Java
Admin
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Ans. The finally keyword is used to create a block of code that follows a try block. A finally block of code always executes, whether or not an exception has occurred.

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 Q20. Will finally be called always if all code has been kept in try block ?Core Java
Admin
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Ans. The only time finally won't be called is if you call System.exit() or if the JVM crashes first.

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 Q21. Will the static block be executed in the following code ? Why ?

class Test
{
static
{
System.out.println("Why I am not executing ");
}
public static final int param=20;
}

public class Demo
{
public static void main(String[] args)
{
System.out.println(Test.param);
}
}
Admin
info@buggybread.com
Ans. No the static block won't get executed as the referenced variable in the Test class is final. Compiler replaces the content of the final variable within Demo.main method and hence actually no reference to Test class is made.

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 Q22. Will static block for Test Class execute in the following code ?

class Test
{
static
{
System.out.println("Executing Static Block.");
}
public final int param=20;

public int getParam(){
return param;
}
}

public class Demo
{
public static void main(String[] args)
{
System.out.println(new Test().param);
}
}
Admin
info@buggybread.com
Ans. Yes.

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 Q23. Can finally block throw an exception ?Core Java
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Ans. Yes.

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 Q24. Why is a constant defined as a static final in Java?Core Java
Admin
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Ans. Final makes sure that the value doesn't change after initialization and static makes sure that there is only one copy that can be shared across objects.

Making it non static will unnecessarily create a different copy per object wherein the same value will kept for all copies ( as its final and cannot be changed ).

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 Q25. Which of the following is not possible ?

a. try block followed by catch
b. try block followed by finally
c. try block followed by catch block and then finally
d. try block without catch or finally block
Anonymous
Ans. try block without catch or finally block

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 Q26. Which of the following is not true for final variables ?

a. They cannot be changed after initialization
b. They can be initialized within static method
c. They can be declared and initialized together at the same place
d. They can be initialized within constructor
Anonymous
Ans. They can be initialized within static method

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 Q27. Which of the following is false for final ?

a. Final methods cannot be overriden
b. Final methods cannot be overloaded
c. Final classes cannot be subclassed
d. Final class cannot be abstract
Anonymous
Ans. Final methods cannot be overloaded

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Rarely asked as it was introduced with Java 8.
 Q28. Which keyword specify that a variable is effectively final ? a. final b. No Keyword c. Both of the above d. None of the aboveCore Java
Anonymous
Ans. No Keyword

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 Q29. Can we add more elements to an array list that has been marked as final ?

Ans. Yes, the array list can hold more elements. Final only puts the restriction that the array list reference cannot hold any other array list.

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 Q30. Why can't we declare a class abstract as well as final ?Core Java

Ans. Abstract means that the class is only meant to be subclassed whereas final means that it cannot be subclassed so both concepts - abstract and final are actually mutually exclusive and hence not permitted together.

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