Interview Questions and Answers for 'Set' | Search Interview Question

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

Frequently asked at Manhattan Associates ( Based on 2 feedback )

Q1. What is a Lambda Expression ? What's its use ?

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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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.

Q2. What is the difference between ArrayList and LinkedList ?

Core Java

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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Frequently asked question in companies using Hibernate.

Q3. What is Lazy Initialization in Hibernate ?

Hibernate

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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Basic and Very Frequently asked.

Q4. What is Polymorphism in Java ?

Core Java

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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Q5. Difference beween HashSet and TreeSet ?

Core Java

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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Frequently asked in Indian Service Companies. Tech Mahindra ( Based on 3 inputs ) and Infosys ( 3 inputs )

Q6. What is the difference between List, Set and Map ?

or

What are the different Java Collections Interfaces ?

Core Java

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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Q7. What is comparator interface used for ?

Core Java

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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Q8. 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

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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Q9. If I try to add Enum constants to a TreeSet, What sorting order will it use ?

Ans. Tree Set will sort the Values in the order in which Enum constants are declared.

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Q10. 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

Ans. Random Order

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Q11. Which are the sorted collections ?

Core Java

Ans. TreeSet and TreeMap

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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");
for(String s: mySet){
System.out.println(s);
}

Ans. It will print 4567,5678 and 6789 but Order cannot be predicted.

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Q13. 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));

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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Q14. 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

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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Q15. Explain Set Interface?

Core Java

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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Q16. What is the best practice configuration usage for files - pom.xml or settings.xml ?

Maven

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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Q17. What ate the getter and setter methods ?

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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Q18. Can we use Ordered Set for performing Binary Search ?

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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Q19. 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);
}

Ans. 4567
5678
6789

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Q20. 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);
}
}

Ans. SUNDAY
MONDAY
SATURDAY

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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 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);
      }
   }
}

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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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

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

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

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

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 ?

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

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.

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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