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Interview Questions and Answers for 'Set' - 48 question(s) found - Order By Newest

next 40
  Q1. What is a Lambda Expression ? What's its use ?Core Java
Admin
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Ans. Its an anonymous method without any declaration.

Lambda Expression are useful to write shorthand Code and hence saves the effort of writing lengthy Code.

It promotes Developer productivity, Better Readable and Reliable code.

  Sample Code for lambda

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Frequently asked question in companies using Hibernate.
  Q2. What is Lazy Initialization in Hibernate ?Hibernate
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Ans. It's a feature to lazily initialize dependencies , relationship and associations from the Database. Any related references marked as @OneToMany or @ManyToMany are loaded lazily i.e when they are accessed and not when the parent is loaded.

  Sample Code for Lazy Initialization

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q3. What is the difference between ArrayList and LinkedList ?Core Java
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info@buggybread.com
Ans. Underlying data structure for ArrayList is Array whereas LinkedList is the linked list and hence have following differences -

1. ArrayList needs continuous memory locations and hence need to be moved to a bigger space if new elements are to be added to a filled array which is not required for LinkedList.

2. Removal and Insertion at specific place in ArrayList requires moving all elements and hence leads to O(n) insertions and removal whereas its constant O(1) for LinkedList.

3. Random access using index in ArrayList is faster than LinkedList which requires traversing the complete list through references.

4. Though Linear Search takes Similar Time for both, Binary Search using LinkedList requires creating new Model called Binary Search Tree which is slower but offers constant time insertion and deletion.

5. For a set of integers you want to sort using quicksort, it's probably faster to use an array; for a set of large structures you want to sort using selection sort, a linked list will be faster.

  Sample Code for ArrayList

  Sample Code for LinkedList

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Basic and Very Frequently asked.
  Q4. What is Polymorphism in Java ?Core Java2016-11-06 09:10:54

Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

  Sample Code for overloading

  Sample Code for overriding

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Frequently asked in Indian Service Companies. Tech Mahindra ( Based on 3 inputs ) and Infosys ( 3 inputs )
  Q5. What is the difference between List, Set and Map ?

or

What are the different Java Collections Interfaces ?
Core Java
Anonymous
Ans. List - Members are stored in sequence in memory and can be accessed through index.
Set - There is no relevance of sequence and index. Sets doesn't contain duplicates whereas multiset can have duplicates.
Map - Contains Key , Value pairs.

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 Q6. Why are Getter and Setter better than directly changing and retrieving fields ?

or

What is the significance of variable hiding in Java ?

or

Why it's preferred to keep variables private and allow their access through getter and setter methods ?
Core Java
Admin
info@buggybread.com
Ans. 1. Methods can participate in runtime polymorphism whereas member variables cannot.

For example -

Vehicle vehicle = new Car();

car.getObjVariable();// will return variable defined in Car

whereas

car.variable

will return the variable from Car class irrespective of the object it holds.

2. Validations can be performed before setting the variables.

3. If the input format changes or some other value or calculated value needs to be returned , that can be absorbed by making change ( wrapping ) in the setter and getter. By this the call to method from outside or interface to the object will remain the same.

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 Q7. In what order the elements of a HashSet are retrieved ?

a. Random Order
b. Insertion Order
c. Natural Sorting Order
d. Inverse Natural Sorting Order
Core Java
Anonymous
Ans. Random Order

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 Q8. Difference beween HashSet and TreeSet ?Core Java2016-11-27 19:08:35

Ans. 1. HashSet doesnt maintain its elements in any specific order and is all random whereas TreeSet maintains elements in natural order 9 order defined by the equals method of TreeSet element type )

2. TreeSet doesnt allow null elements whereas HashMap does.

3. As TreeSet orders elements and is hence insertion is comparatively slower.

4. HashSet performs basic operations like add(), remove(), contains(), size() etc. in a constant size time. A TreeSet performs these operations at the order of log(n) time.

5. HashMap in Java internally backs a HashSet. A NavigableMap backs a TreeSet internally.

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 Q9. What is comparator interface used for ?Core Java
Admin
info@buggybread.com
Ans. The purpose of comparator interface is to compare objects of the same class to identify the sorting order. Sorted Collection Classes ( TreeSet, TreeMap ) have been designed such to look for this method to identify the sorting order, that is why class need to implement Comparator interface to qualify its objects to be part of Sorted Collections.

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 Q10. If I try to add Enum constants to a TreeSet, What sorting order will it use ?
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Ans. Tree Set will sort the Values in the order in which Enum constants are declared.

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 Q11. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}
admin
info@buggybread.com
Ans. It will print 4567,5678 and 6789 but Order cannot be predicted.

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 Q12. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
System.out.println(s.get(0));
admin
info@buggybread.com
Ans. This will give compile time error as we cannot retrieve the element from a specified index using Set. Set doesn't maintain elements in any order.

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 Q13. Explain Set Interface?Core Java
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Ans. It is a collection of element which cannot contain duplicate elements. The Set interface contains only methods inherited from Collection and adds the restriction that duplicate elements are prohibited.

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 Q14. What is the best practice configuration usage for files - pom.xml or settings.xml ?Maven
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Ans. The best practice guideline between settings.xml and pom.xml is that configurations in settings.xml must be specific to the current user and that pom.xml configurations are specific to the project.

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 Q15. What ate the getter and setter methods ?
Admin
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Ans. getters and setters methods are used to store and manipulate the private variables in java beans. A getters as it has name, suggest retrieves the attribute of the same name. A setters are allows you to set the values of the attributes.

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 Q16. Can we use Ordered Set for performing Binary Search ?
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Ans. We need to access values on the basis of an index in Binary search which is not possible with Sets.

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 Q17. Which are the sorted collections ?Core Java
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Ans. TreeSet and TreeMap

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 Q18. What will be the output of this code ?

Set mySet = new TreeSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}
admin
info@buggybread.com
Ans. 4567
5678
6789

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 Q19. 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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 Q20. 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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 Q21. 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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 Q22. public class BuggyBread1{

public static void main (String args[]) {
Set<String> mySet = new TreeSet<String>();
mySet.add(""1"");
mySet.add(""2"");
mySet.add(""111"");
for(String d: mySet){
System.out.println(d);
}
}
}
Core Java
Admin
info@buggybread.com
Ans. 1
111
2

TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in String has been defined such that it results in the natural alphabetic Order. Here the elements in the TreeSet are of String and not of Integer. In String Natural Order, 111 comes before 2 as ascii of 1st character first determines the order.

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 Q23. public class BuggyBread1{

public static void main (String args[]) {
Set<Integer> mySet = new TreeSet<Integer>();
mySet.add(1);
mySet.add(2);
mySet.add(111);
for(Integer d: mySet){
System.out.println(d);
}
}
}
Core Java
Admin
info@buggybread.com
Ans. 1
2
111

TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in Integer has been defined such that it results in the natural numerical Order.

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 Q24. How is HashSet maintained in memory by Java ?Core Java
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Ans. HashSet is maintained as HashMap by Java with values of the HashSet as Keys of the HashMap and value of the HashMap as the constant PRESENT.

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 Q25. What is classpath in a project?Core Java
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Ans. ClassPath is the path where Java looks for class files to resolve the dependencies. For example - If you are using a class "xyz" in your code and have specified the respective import, Where should Java look for the definition of xyz. Java determines using the class path settings.

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 Q26. Name few classes that implement Set interface ?
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Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_78.html

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 Q27. How many elements will be there in TreeSet after the last line and Why ?

TreeSet set = new TreeSet();
set .add(new String("abc"));
set .add(new String("abc"));
Core Java
Admin
info@buggybread.com
Ans. One.

As we haven't specified the type of TreeSet, it being evaluated with the first element insertion. Once it's identified that it's of type String and as no comparator has been defined, the comparison is done using the String compareTo method. String compareTo method compares the elements by the content / value.

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 Q28. 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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 Q29. Write a method to convert all elements of a set to lower case.Core Java

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?keyword=Method+to+convert+all+elements+of+a+collection&category=code

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 Q30. Write code to sort elements of a set

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?&category=code&searchOption&keyword=952

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 Q31. What is unmodifiable set / unmodifiable map ? How can we create one ?

Ans. It is an unmodifiable / read only view of the underlying collection. We can use

Collections.unmodifiableSet(Set set)
Collections.unmodifiableMap(Map map)
Collections.unmodifiableCollection(Collection collection)

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 Q32. Is it advisable to set the member variables through constructors instead of setting them through setters ? 2016-06-11 10:24:34

Ans. Yes , If the values to be set are known at the time of initialization and doesn't involve polymorphic behavior.If it's using Dependency Injection , then Constructor injection must be available. If it suffice the above conditions, then definitely its advisable to have them set through constructor as they eagerly load the values into the memory and save it fro multiple values assignment ( one through default constructor and then through assignment )

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Frequently asked in Alibaba (Based on 2 feedback)
 Q33. What is the best Memory setting for JVM ?Core Java2016-12-13 10:18:56

Ans. In Java JVM memory settings is done by use the arguments -Xms -Xmx. Use M or G after the numbers for indicating Megs and Gigs of bytes respectively. -Xms indicates the minimum and -Xmx the maximum.

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   Like         Discuss         Correct / Improve     jvm  memory management  jvm best memory setting     Asked in 1 Companies      intermediate


Frequently asked in Accenture.
  Q34. What is your biggest achievement at work ?General2016-12-15 14:14:22

Ans. [Open Ended Answer]

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   Like         Discuss         Correct / Improve     general question  non technical question     Asked in 20 Companies        frequent


 Q35. What is an Asset store ?IBM WCS2017-02-02 14:45:56

Ans. Asset stores are collections of sharable resources (business artifacts, business processes and storefront assets) that can be leveraged in other stores.

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   Like         Discuss         Correct / Improve     asset store


  Q36. What are the core OOPs concepts ?Core Java2017-02-06 16:15:55

Ans. Abstraction, Encapsulation, Polymorphism , Composition and Inheritance

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 Q37. What is a mutator in Java?Core Java2017-03-10 09:45:05

Ans. Mutator is another name for setter methods, i.e the method allows for mutating the property of an object and eventually the state of the object.

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 Q38. What is the quickest way to find count of duplicate elements in an arraylist, without using iteration or loops ?Core Java2017-06-09 08:19:17

Ans. We can copy the elements to a Set and then find the difference of count between ArrayList and Set. As Set don't allow duplicates , they will be removed in the set.

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 Q39. How can we set a key within Redis ?Redis2017-06-16 09:03:26

Ans. SET <KEY_NAME> <VALUE>

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 Q40. As root, if you have to assign the owner for the file and set only read permission for the owner, Write a unix command to do it.Unix2017-08-10 16:56:27

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


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