Part 16
Interview questions on Collections in java for experienced covered in this post:
What is the Iterator and why do we require iterator in Collection framework?
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Basically, Iterator is an interface.
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Iterator can be used to traverse throughout the collection
object.
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Iterator is a universal iterator that can apply to all types
of collection like list, set, map.
-
The iterator has three methods to perform the operation.
1.
hasNext();
2.
next();
3.
remove();
 
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What is the ListIterators and why do we require ListIterators in Collection framework?
-
ListIterator is a child interface of the Iterator
interface.
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ListIterator is an iterator can be applicable to list
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List iterator can move bidirectionally.
-
There are 9 methods present inside ListIterator which are as
follows.
1.
hasNext();
2.
next();
3.
nextIndex();
4.
hasPrevious();
5.
previous();
6.
previousIndex();
7.
remove();
8.
add();
9.
set();
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package
simplifiedjava.crackedInterview;
import
java.util.ArrayList; import java.util.ListIterator;
public
class
ListIteratorDemo {
public
static
void
main(String[] args) {
ArrayList<Integer> list
= new
ArrayList<Integer>();
list.add(10);
list.add(20);
list.add(30);
list.add(40); list.add(50); ListIterator<Integer> itr = list.listIterator();
while(itr.hasNext()) {
int
no
= itr.next();
System.out.println(no);
boolean
result
= itr.hasNext();
System.out.println(result);
}
} }
Output:
10
true
20
true
30
true
40
true
50 false |
What is the Enumarator and why do we require Enumarator in Collection framework?
-
Enumeration can be used to iterate the legacy classes.
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Enumeration is also a legacy interface.
-
Please refer to the below example.
|
package simplifiedjava.crackedInterview;
import
java.util.Enumeration; import java.util.Vector; public class EnumerationDemo {
public
static
void
main(String[] args) {
Vector<Integer> v
= new
Vector<Integer>();
v.addElement(10);
v.addElement(20);
v.addElement(30); v.addElement(40);
Enumeration<Integer> enu
= v.elements();
while(enu.hasMoreElements()) {
int
element
= enu.nextElement();
System.out.println(element);
}
}
}
Output:
10
20
30
40 |
-
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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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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