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Core Java - Interview Questions and Answers for 'Enums' - 22 question(s) found - Order By Newest

 Q1. Enums cannot be declared ..

a. private
b. public
c. static
d. final
Core Java
Anonymous
Ans. final

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 Q2. What are concepts introduced with Java 5 ?Core Java
Anonymous
Ans. Generics , Enums , Autoboxing , Annotations and Static Import.

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   Like         Discuss         Correct / Improve     java   java5   generics   enum   autoboxing   annotations   static import        rare

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 Q3. Can we override compareTo method for Enumerations ?Core Java
Admin
info@buggybread.com
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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   Like         Discuss         Correct / Improve     java   compareto   final methods   enum   enumeration      expert


 Q4. enums are intrinsically ..

a. private
b. public
c. static
d. final
Core Java
Anonymous
Ans. static

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 Q5. What is an Enum type ?Core Java
Anonymous
Ans. An enum type is a special data type that enables for a variable to be a set of predefined constants

  Sample Code for enum

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 Q6. If I try to add Enum constants to a TreeSet, What sorting order will it use ?
Admin
info@buggybread.com
Ans. Tree Set will sort the Values in the order in which Enum constants are declared.

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   Like         Discuss         Correct / Improve     java   collections   set   treeset   enum   sorting   technical lead


 Q7. When were Enums introduced in Java ?
Anonymous
Ans. Enums were introduced with java 5.

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 Q8. What is an enumeration?Core Java
Admin
info@buggybread.com
Ans. An enumeration is an interface containing methods for accessing the underlying data structure from which the enumeration is obtained. It allows sequential access to all the elements stored in the collection.

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 Q9. public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}

public class Test {
Set mySet = new HashSet();
mySet.add(Day.MONDAY);
mySet.add(Day.SUNDAY);
mySet.add(Day.SATURDAY);

for(Day d: mySet){
System.out.println(d);
}
}
admin
info@buggybread.com
Ans. SUNDAY
MONDAY
SATURDAY

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   Like         Discuss         Correct / Improve     enum   set   collections   hashset   coding   code

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 Q10. What will be the output of the following code ?

enum Day {
   MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}

public class BuggyBread1{
   public static void main (String args[]) {
      Set mySet = new HashSet();
      mySet.add(Day.SATURDAY);
      mySet.add(Day.WEDNESDAY);
      mySet.add(Day.FRIDAY);
      mySet.add(Day.WEDNESDAY);
      for(Day d: mySet){
         System.out.println(d);
      }
   }
}
Admin
info@buggybread.com
Ans. FRIDAY , SATURDAY and WEDNESDAY will be printed but the order cannot be determined.

Only one FRIDAY will be printed as Set doesn't allow duplicates. Order cannot be determined as HashSet doesn't maintain elements in a particular order. 

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 Q11. What will be the output of the following code ?

enum Day {
MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}

public class BuggyBread1{
public static void main (String args[]) {
Set mySet = new TreeSet();
mySet.add(Day.SATURDAY);
mySet.add(Day.WEDNESDAY);
mySet.add(Day.FRIDAY);
mySet.add(Day.WEDNESDAY);
for(Day d: mySet){
System.out.println(d);
}
}
}
Core Java
Admin
info@buggybread.com
Ans. WEDNESDAY
FRIDAY
SATURDAY

Only one FRIDAY will be printed as Set doesn't allow duplicates.Elements will be printed in the order in which constants are declared in the Enum. TreeSet maintains the elements in the ascending order which is identified by the defined compareTo method. compareTo method in Enum has been defined such that the constant declared later are greater than the constants declared prior.

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 Q12. Can we extend an Enum ?Core Java
Admin
info@buggybread.com
Ans. No. Enums are final by design.

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 Q13. Shall we keep the enumeration name in all capital letters as it contains all constants ?
Admin
info@buggybread.com
Ans. Enum is actually a class with pre defined constants. So enum name should follow the convention of the Class name. Though the constant names or the Enum variables should follow the convention of having all capital letters.

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 Q14. In Hibernate, While defining Criteria, Have you ever faced any problem while adding restrictions with user defined types or Enums ?Hibernate
Admin
info@buggybread.com
Ans. Yes, with Enum as was getting an exception while doing equality check for enum field.

got it fixed by adding @Enumerated(EnumType.STRING) to the field in entity.

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 Q15. Name few Enum classes and interfaces provided by Java ?
Admin
info@buggybread.com
Ans. http://www.buggybread.com/2015/01/java-enum-classes-and-interfaces.html

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 Q16. If we add Enum constants to a sorted collection ( Treemap , TreeSet ), What will be the order in which they will be maintained ?

a. Sorted Collection wont maintain them in any order.
b. Insertion Order
c. Order in which constants are declared.
d. Natural Sorting Order.
Anonymous
Ans. Order in which constants are declared.

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   Like         Discuss         Correct / Improve     enum   collections   sorted collections   treemap   treeset   compareto   comparable   java


 Q17. Can Enum be a replacement for a constant file in majority of the situation ?Design2016-08-11 16:21:25

Ans. Yes , it can be but it may not be an optimal alternative if we need to change the values frequently. As Enum is compiled like any Java File , any change requires the application to be rebuild , deployed and restart.

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 Q18. What is the difference between Enumeration and Iterator ?Core Java2017-05-07 15:22:08

Ans. Enumeration can iterate only legacy collections like Vector , HashTable and Stack whereas Iterator can iterate both legacy and non legacy collections.

Enumeration is less safer than Iterator

Enumeration is fail safe whereas Iterator is fail fast

Iterator allows for removal of element while traversal whereas Enumeration doesn't have remove method.

Enumerations were introduced in Java 1 whereas Iterators were introduced with Java 2

Enumerations have methods like hasMoreElements and nextElement whereas Iterators have methods like hasNext, next and remove

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   Like         Discuss         Correct / Improve     enumeration vs iterator  collections      Basic        frequent


 Q19. Can an enum extend another enum ?Core Java2017-08-15 14:02:56

Ans. No

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 Q20. Can we have a sub enum within an enum ?Core Java2017-08-15 14:03:15

Ans. Yes

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 Q21. What will happen if there are no enums in Java ?Core Java2018-12-11 16:18:29

Ans. Enums in Java is a facility to have objects upfront and use them as constants. Even if such a facility is not available , a workaround could be achieved.

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 Q22. How is the declaration of enum in Typescript differ from Javascript ?TypeScript2020-01-23 13:32:44

 This question is still unanswered. Can you please provide an answer.


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