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Interview Questions and Answers - Order By Newest

   
 Q31. 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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   Like         Discuss         Correct / Improve     ebay   collections   arraylist   final keyword


 Q32. 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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 Q33. Can you assign value to a static final type at runtime ?Core Java
Ans. No

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   Like         Discuss         Correct / Improve     static  final  static final     Asked in 1 Companies


 Q34. What is the advantage of using static final or constant variables in Java ? Core Java
Ans. Better Control - If the value is being used at multiple locations , that can be controlled better from single place. Any change would only require making single change.

Meaning , Aliasing and Better Readability - Sometimes its easy to read the value by its meaning or alias ( 0 as ZERO or 0 as NEUTRAL_VALUE ).


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   Like         Discuss         Correct / Improve     static final  final variable  variable constants


 Q35. Will finally run if we have return statement and it exits the method early ?Core Java
Ans. finally will execute in all graceful situations - graceful executions as well as graceful exceptions. The only situation when finally block won't execute is when the app is abruptly stopped, killed or unplugged.

  Sample Code for finally

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 Q36. If we have to maintain a value "7" denoting "number of days in a week" as constant variable, Which of the following is the best constant name and Why ?

SEVEN
NUMBER_OF_DAYS_IN_WEEK
NUMBER_OF_DAYS_IN_WEEK_7
Core Java
Ans. NUMBER_OF_DAYS_IN_WEEK

Constant should be such that it uniquely identifies the value it holds and context of the value. SEVEN uniquely identifies the value but doesn't express the context.

Though NUMBER_OF_DAYS_IN_WEEK and NUMBER_OF_DAYS_IN_WEEK_7 makes sense in terms of unique value identification and context but 7 at the end of constant name appears useless as all weeks have 7 days and hence it's the only value it can hold. If it would have been "number of days in a month", it would have made sense to include number of days at the end like

NUMBER_OF_DAYS_IN_MONTH_30
NUMBER_OF_DAYS_IN_MONTH_31
NUMBER_OF_DAYS_IN_MONTH_27
NUMBER_OF_DAYS_IN_MONTH_28

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   Like         Discuss         Correct / Improve     constant variables  static final variable  java conventions  java naming conventions


 Q37. If we have to maintain a value "31" denoting "number of days in a month" as constant variable, Which of the following is the best constant name and Why ?

THIRTY_ONE
NUMBER_OF_DAYS_IN_MONTH
NUMBER_OF_DAYS_IN_MONTH_31
Core Java
Ans. NUMBER_OF_DAYS_IN_MONTH_31

Constant should be such that it uniquely identifies the value it holds and context of the value. THIRTY_ONE uniquely identifies the value but doesn't express the context. NUMBER_OF_DAYS_IN_MONTH expresses the context but doesn't specify the value clearly as different month can have different number of days.


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   Like         Discuss         Correct / Improve     constant variables  static final variable  java conventions  java naming conventions


 Q38. Would you consider creating a constant name for "null" ?

Core Java
Ans. Objective of constant variable is to provide a context to the value and provide a single point of change. In terms of context, i don't see much need for having constant name for null as null is already self explanatory. In terms of providing single point of change, it doesn't make much sense as it would necessitate that all such placeholders either hold null or a common value.



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 Q39. What is a blank final variable ? Can we initialize a blank final variable ?Core Java
Ans. A final variable that is not initialized while declaration is a blank final variable.

Yes, we can initialize it within a constructor.

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 Q40. Which of following is / are valid static final declaration ?

public static final String MAX_NUM = "10";
public static final Object NULL = null;
public static final MathContext MATH_CONTEXT = new MathContext(2,RoundingMode.CEILING);
Core Java
Ans. All are valid declarations.

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 Q41. What is the use of final keyword ?Core Java
Ans. final keyword is a modifier that means differently when applied to variables, methods and classes.

1. Final variable cannot be changed once initialized
2. Final method cannot be overridden
3. Final class cannot be sub classed

  Sample Code for final variable

  Sample Code for final method

  Sample Code for final class

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   Like         Discuss         Correct / Improve     final  final keyword     Asked in 1 Companies      Basic        frequent


 Q42. How do we define constant variables in Java ?Core Java
Ans. By using static and final modifiers.

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   Like         Discuss         Correct / Improve     constant variables   static final      basic        frequent


 Q43. Will the following code compile ?

final HashMap hm = new HashMap();
hm.put("Ravi", 221);
Core Java
Ans. Yes, it will compile without error. final in this context means that the reference hm cannot be assigned to a new hash map but didn't restrict from changing the state of collection already held by hm.

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   Like         Discuss         Correct / Improve     final  final variable     Asked in 1 Companies


 Q44. What is the difference between being final and being immutable ? Are string final or immutable in Java ?Core Java
Ans. Being final in the sense of objects or object reference means that the reference cannot be reassigned to a different object whereas being immutable means that the object contents cannot be changed.

Strings in Java are immutable.

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 Q45. How different is it when final applied to variables and object references ? Core Java
Ans. final when assigned to object references doesn't make them immutable. It means that the references cannot be de-referenced.

final when applied to variables means that the value cannot be changed.

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 Q46. What will the following code print and Why

class Class1 {
static{
System.out.println("Wow");
}
public static final int xyz=1;
}

class Class2{
public static void main(String[] args) {
System.out.println(String.valueOf(Class1.xyz));
}
}
Core Java
Ans. 1

Reason being that Class1.xyz is replaced with 1 during pre compilation only and a reference to Class1 is never made.

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 Q47. What will happen if there is an exception in Java finally block ?Core Java
Ans. The regular behavior of exception handling will occur. It will look for any immediate catch handler and if none is provided, it would be transmitted to the callers until a catch handler is found or it's out of main function.

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   Like         Discuss         Correct / Improve     exceptions  finally


 Q48. Why Java has final class ?Core Java
 This question was recently asked at 'Avis'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     final class   final keyword     Asked in 1 Companies      basic


 Q49. Are final methods faster than regular instance methods ?Core Java
Ans. Yes. As they cannot be overridden , there is no use of virtual table concept which is used for dynamic binding resolution.

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   Like         Discuss         Correct / Improve     final methods   final keyword      expert


 Q50. Can constructors be final ?Core Java
Ans. No. They are never inherited and therefore are not subject to hiding or overriding.

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 Q51. If we have a return statement inside the finally block, Then what will happen ?Core Java
Ans. Returning from inside a finally block will cause exceptions to be lost. A return statement inside a finally block will cause any exception that might be thrown in the try block to be discarded.

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 Q52. Which of the following methods are used by Java Garbage Collection Mechanism ?Core Java
a. final
b. finally
c. finalize
d. All of the above

Ans.c. finalize

 Q53. In which case finally won't get executed ?Core Java
a. in case of exception
b. in case of normal execution
c. in case of return statement before end of try block
d. in case of force program termination

Ans.d. in case of force program termination

 Q54. Which of the following class cannot be extended or inherited ?

StringBuffer , StringBuilder
Core Java
a. StringBuffer
b. StringBuilder
c. Both cannot be extended
d. Both can be extended

Ans.c. Both cannot be extended

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