Part 6
Interview questions on Collections in java for experienced covered in this post:
What is Blocking Queue? What are the types of Blocking Queue?
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A blocking queue is a queue that blocks when you try to
dequeue from it.
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The queue is empty or if you try to enqueue objects to it and
the queue is already full.
-
A Queue that additionally supports operations that wait for
the queue to become non-empty when retrieving an element, and wait for space
to become available in the queue when storing an element.
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A BlockingQueue does not accept null elements.
Implementations throw NullPointerException on attempts to add, put or offer
a null. A null is used as a sentinel value to indicate the failure of poll
operations.
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BlockingQueue implementations are designed to be used
primarily for producer-consumer queues, but additionally, support the
Collection interface.
-
For example, it is possible to remove an arbitrary element
from a queue using remove(x). However, such operations are in general not
performed very efficiently, and are intended for only occasional use, such
as when a queued message is cancelled.
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BlockingQueue implementations are thread-safe.
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All queuing methods achieve their effects atomically using
internal locks or other forms of concurrency control.
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A BlockingQueue does not intrinsically support any kind of
"close" or "shutdown" operation to indicate that no more items will be
added.
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A BlockingQueue belongs to java.util.concurrent.BlockingQueue
package.
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Following are the
types of BlockingQueue.
1.
PriorityBlockingQueue.
2.
LinkedBlockingQueue.
3.
ArrayBlockingQueue.
What is CircularQueue? What are the advantages of CircularQueue?
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Circular Queue is a linear data structure in which the
operations are performed based on FIFO (First In First Out) principle.
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The last element is connected back to the first element to
make a circle.
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CircularQueue is also called 'Ring Buffer'.
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Circular queue is used in memory management and Process
Scheduling.
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Advantages of
Circular Queue:
1.
All operations occur in constant time.
2.
Doesn’t use dynamic memory.
3.
No Memory leaks.
4.
Simple Implementation.
5.
Plays an important role in memory management.
 
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Which data structure has implemented LIFO strategy?
-
Stack data structure has implemented LIFO (Last In First Out)
strategy.
-
Please refer to the below example.
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package simplifiedjava.crackedInterview; import java.util.Stack; public class StackDemo {
public
static
void
main(String[] args) {
Stack<Integer> s
= new
Stack<Integer>();
s.push(10);
s.push(20);
s.push(30);
System.out.println(s);
s.pop();
System.out.println(s);
}
}
Output:
[10, 20, 30]
[10, 20] |
- Graphical representation of Stack implementation.
Explain the defined method in Stack?
-
In Stack there are 5 main methods can be used to perform
basic operations.
1.
Push(Object O):
To insert an object into stack.
2.
Pop(): To remove
and return top of the stack.
3.
Peek(): To
return top of the object without removing it.
4.
Empty(): return
true if the stack is empty.
5.
Search():
returns offset if the element is available otherwise, returns -1.
Which data structure has implemented FIFO strategy?
-
Queue data structure has implemented FIFO (First In First
Out) strategy.
-
Please refer to the below example.
|
package simplifiedjava.crackedInterview;
import
java.util.LinkedList; import java.util.Queue; public class QueueDemo {
public
static
void
main(String[] args) {
Queue<Integer> queue
= new
LinkedList<Integer>();
queue.offer(10);
queue.offer(20);
queue.offer(30);
System.out.println(queue);
queue.peek();
System.out.println(queue);
queue.poll();
System.out.println(queue);
}
}
Output:
[10, 20, 30]
[10, 20, 30]- Pick() just retrieved the value but not
removed.
[20, 30] – Poll() retrieved the value and removed as well.
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- Graphical Representation of Queue.
Explain the defined method in Queue?
-
There are 5 main methods defined in Queue.
1.
Offer(Object o):
Add object in queue.
2.
Peek(): return
head element of queue. If queue is null then it will return null.
3.
Element():
return head element of queue. If the queue is null the it will throw
NoSuchElementException.
4.
Poll(): returns
head element of queue and remove. If the queue is empty then it will return
null.
5.
Remove():
returns head element of queue and remove. If queue is empty then it will
throw NoSuchElementException.
Explain deque interface? What is the importance of deque interface?
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A Deque is a double-ended-queue.
-
A double-ended-queue is a linear collection of elements that
supports the insertion and removal of elements at both endpoints.
-
The Deque interface is a richer abstract data type than both
Stack and Queue because it implements both stacks and queues at the same
time.
-
The Deque interface, defines methods to access the elements
at both ends of the Deque instance.
-
Methods are provided to insert, remove, and examine the
elements.
-
Predefined classes like ArrayDeque and LinkedList implement
the Deque interface.
-
Note that the Deque interface can be used both as
last-in-first-out stacks and first-in-first-out queues.
-
Advantages of
Deque.
1.
Deques are faster in adding/removing elements to the end or
beginning.
2.
Lists are faster in adding/removing elements to any other
'middle' position.
3.
You can also use insert (index, value) on lists, while on
deques you can only append left or right.
-
Java interview questions and answers all MNC - Click here
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Basic core java interview questions and answers for freshers
- Click here
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Core java interview questions for 3 years experience
- Click here
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Core java interview questions and answers for 3-5 years exp
- Click here
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Core java interview questions and Answers for 5 - 7 Years exp
- Click here
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Basic Java Interview Questions and Answers - Click here
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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
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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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Thank you techies for visiting this blog. I hope you enjoyed this blog and got more technical knowledge. I have tried to cover all types of questions and provided examples tested on eclipse as much as I can. Guys, please don’t just mug up the questions and answers. Try to clear your concepts with examples. Try to write a code on eclipse once you read the concepts. It will help you to memorize the concepts for a very long time. Simultaneously you will be prepared for interview programs as well. It will help you to survive in the IT sector for a long time. It may be easy to crack an interview but it's really tough to survive in the IT industry with inadequate knowledge and skills. I have collected all the questions from actual interviews attended by my friends, colleagues, college mate and classmate. I have covered frequently asked questions as well as challenging questions. I have included many programs to understand the concept thoroughly. I will try to explain the concept with the help of a real-time program in eclipse. You can share more questions which are not covered in this blog or post. Always welcome your suggestions and queries. I will definitely try to resolve it. Please comment your queries and new set of questions under the comment sections. I will create a new post for those questions.
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