Part 5
Interview questions on Collections in java for experienced covered in this post:
What is NavigableSet?
-
The Java NavigableSet interface, java.util.NavigableSet, is a
subtype of the Java SortedSet interface.
-
Therefore the NavigableSet behaves like a SortedSet, but with
an additional set of navigation methods available in addition to the sorting
mechanisms of the SortedSet.
-
A NavigableSet may be accessed and traversed in either
ascending or descending order.
-
The descendingSet() method returns a view of the set with the
senses of all relational and directional methods inverted.
-
NavigableSet reverse = original.descendingSet(); also returns
the reverse order.
-
This interface additionally defines methods pollFirst and
pollLast that return and remove the lowest and highest element, if one
exists, else returning null.
-
Methods subSet, headSet, and tailSet differ from the
like-named SortedSet methods in accepting additional arguments describing
whether lower and upper bounds are inclusive versus exclusive.
-
Implementation class of NavigableSet is java.util.TreeSet
class.
-
Subsets of any NavigableSet must implement the NavigableSet
interface.
-
Create a NavigableSet.
1.
NavigableSet navigableSet = new TreeSet();
-
Please refer to the below example.
|
package simplifiedjava.crackedInterview;
import
java.util.NavigableSet; import java.util.TreeSet; public class NavigableSetDemo {
public
static
void
main(String[] args) {
NavigableSet<Integer> set
= new
TreeSet<Integer>();
set.add(50);
set.add(10);
set.add(30);
set.add(20);
set.add(40);
System.out.println("Actual Set : "
+ set);
System.out.println("Lower value of 30 using lower()
= "+ set.lower(30));
System.out.println("Higher value of 30 using floor() = "+ set.floor(30));
System.out.println("Lowest value of 30 using ceiling() = "+ set.ceiling(30));
System.out.println("Lowest value of 30 using higher()
= "+ set.higher(30));
System.out.println("Lowest value of 30 using pollFirst() = "+ set.pollFirst());
System.out.println("Lowest value of 30 using pollLast() = "+ set.pollLast());
NavigableSet<Integer> reverse
= set.descendingSet();
System.out.println("Reverse Set : "
+ reverse);
}
}
Output:
Actual Set : [10, 20, 30, 40, 50]
Lower value of 30 using lower()
=
20
Higher value of 30 using floor() =
30
Lowest value of 30 using ceiling() = 30
Lowest value of 30 using higher()
= 40
Lowest value of 30 using pollFirst() = 10
Lowest value of 30 using pollLast() = 50 Reverse Set : [40, 30, 20] |
What is the TreeSet? How the object will be stored in Treeset?
-
TreeSet stores the object in sorted and ascending order.
-
TreeSets underlying data structure is a balanced tree.
-
Duplicate objects are not allowed.
-
Insertion order not preserved.
-
Homogeneous objects are allowed.
-
Heterogeneous (Different types of Object) objects are not
allowed otherwise we will get ClassCastException.
-
Null insertion is not possible otherwise you will get
NullPointerException.
-
TreeSet is Serializable because TreeSet implements a
Serializable interface.
-
TreeSet is Clonable because TreeSet implements a Clonable
interface.
-
TreeSet has not implemented RandomAccess.
-
All objects will be inserted based on some sorting order. It
may be a default sorting order or customized sorting order.
-
Please refer to the below example.
|
package simplifiedjava.crackedInterview;
import
java.util.Iterator; import java.util.TreeSet; public class TreeSetDemo {
public
static
void
main(String[] args) {
TreeSet<Integer> set
= new
TreeSet<Integer>();
set.add(50);
set.add(10);
set.add(30);
set.add(20);
set.add(40);
System.out.println("Original Set : "
+ set);
TreeSet<Integer> reverse
= (TreeSet<Integer>) set.descendingSet(); System.out.println("Reverse Set : " + reverse);
// Reverse using iterator
Iterator<Integer> itr
= set.descendingIterator();
System.out.println("Using Iterator : ");
while(itr.hasNext()) {
int
i
= (int)itr.next();
System.out.print(i+ ", ");
}
}
}
Output:
Original Set : [10, 20, 30, 40, 50]
Reverse Set : [50, 40, 30, 20, 10]
50, 40, 30, 20, 10, |
 
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Can we insert null in TreeSet? If not then why it is not possible?
-
We cannot insert null in TreeSet.
-
TreeSet internally stores the elements according to some
sorting order.
-
While inserting records into the tree set JVM always compare
the two values and while comparing you might get NullPointerException.
What is importance of emptySet() method in collection framework?
-
An emptySet() method can be used to get the set which is
empty.
What are the characteristics of Queue Interface?
-
Queue interface is used to hold the element about to be
processed in FIFO(First In First Out).
-
A Queue is a collection for holding elements prior to
processing.
-
Queue is a child interface of the Collection interface.
-
Besides basic Collection operations, queues provide
additional insertion, removal, and inspection operations.
-
Please refer the queue interface and its method.
|
public interface Queue<E> extends Collection<E> {
E
element();
boolean
offer(E e);
E
peek();
E
poll();
E
remove();
} |
What is Priority Queue?
-
If we want to represent a group of individual objects prior
to processing according to some priority then it is called Priority
Queue.
-
Priority can be natural sorting order or customized sorting
order defined by the comparator.
-
Insertion order is not preserved. It is based on some
priority.
-
Duplicate objects are not allowed.
-
Null is not allowed.
-
If we are
depending on natural sorting order then objects must implement a comparable
interface or it should be homogeneous. Otherwise, we will get
ClassCastException.
-
If we are defining our own Comparator then there is no need
to have homogeneous object.
-
Please refer to the below two examples.
|
package simplifiedjava.crackedInterview;
import
java.util.Comparator; import java.util.PriorityQueue; public class PriorityQueueDemo {
public
static
void
main(String[] args) {
PriorityQueue<String> q
= new
PriorityQueue<>(new
DecendingQueueComparator());
q.offer("Shweta");
q.offer("Shruti"); q.offer("Arpita");
while(!q.isEmpty()) {
System.out.println(q.poll().toString());
}
} } class DecendingQueueComparator implements Comparator<String>{
@Override
public
int
compare(String s1, String s2) {
return
s2.compareTo(s1);
}
}
Output:
Shweta
Shruti Arpita // Ascending Order. package simplifiedjava.crackedInterview;
import
java.util.Comparator; import java.util.PriorityQueue; public class PriorityQueueDemo {
public
static
void
main(String[] args) {
PriorityQueue<String> q
= new
PriorityQueue<>(new
AscendingQueueComparator());
q.offer("Shweta");
q.offer("Shruti"); q.offer("Arpita");
while(!q.isEmpty()) {
System.out.println(q.poll().toString());
}
} } class AscendingQueueComparator implements Comparator<String>{
@Override
public
int
compare(String s1, String s2) {
return
s1.compareTo(s2);
}
}
|
-
Java interview questions and answers all MNC - Click here
-
Basic core java interview questions and answers for freshers
- Click here
-
Core java interview questions for 3 years experience - Click here
-
Core java interview questions and answers for 3-5 years exp
- Click here
-
Core java interview questions and Answers for 5 - 7 Years exp
- Click here
-
Basic Java Interview Questions and Answers - Click here
-
Java interview questions and answers on oops - Click here
-
Java interview questions and answers on Strings - Click here
-
Java interview questions on exception handling - Click here
-
Interview questions on multithreading in java for experienced
- Click here
-
Interview questions on serialization in java for experienced
- Click here
-
Interview questions on inner class in java for experienced
- Click here
-
Interview questions on Collections in java for experienced
- Click here
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