80 Java Collections Interview Questions and Answers
(2022)
Here are Java Collections Interview Questions for fresher as well as experienced candidates to get their
dream job.
1) What is framework in Java?
A framework is a popular and readymade architecture that contains a set of classes and interfaces.
2) What is the Collection framework in Java?
Collection Framework is a grouping of classes and interfaces that is used to store and manage the objects.
It provides various classes like Vector, ArrayList, HashSet, Stack, etc. Java Collection framework can also
be used for interfaces like Queue, Set, List, etc.
3) Explain Collections Class
java.util.Collections is a class consists of static methods that operate on collections. It contains polymorphic
algorithms to operate on collections, “wrappers”. This class contains methods for algorithms, like binary
sorting, search, shuffling, etc.
,4) What is the hashCode()?
The hashCode() is a method that returns an integer hash code.
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5) Distinguish between ArrayList and Vector in the Java collection framework.
ArrayList Vector
ArrayList is cannot be synchronized. Vector can be is synchronized.
It is not a legacy class. It is a legacy class.
It can increase its size by 50% of the size of the array. It can increase its size by doubling the size of the array.
ArrayList is not thread-safe. Vector is a thread-safe.
6) What is ArrayList in Java?
ArrayList is a data structure that can be stretched to accommodate additional elements within itself and
shrink back to a smaller size when elements are removed. It is a very important data structure useful in
handling the dynamic behavior of elements.
, 7) Differentiate between Iterator and ListIterator
The difference between Iterator and ListIterator is:
Iterator ListIterator
The Iterator can traverse the array elements in the ListIterator can traverse the array elements in backward as well as
forward direction. forward directions.
It can be used in Queue, List, and Set. It can be used in List.
It can perform add, remove, and set operation while traversing the
It can perform only remove operation.
collection.
8) What is the difference between Iterator and Enumeration?
The difference between Iterator and Enumeration
Iterator Enumeration
The Iterator can traverse both legacies as well as non-legacy
Enumeration can traverse only legacy elements.
elements.
The Iterator is fail-fast. Enumeration is not fail-fast.
The Iterator is very slow compare to Enumeration. Enumeration is fast compare to Iterator.
The Iterator can perform remove operation while traversing the The Enumeration can perform only traverse operation on the
collection. collection.
9) Define BlockingQueue
BlockingQueue is an interface used in Java that can extend the Queue. It provides concurrency in various
queue operations like retrieval, insertion, deletion, etc.
The Queue waits to become non-empty at the time of retrieving any elements. BlockingQueue should not
contain null elements. The implementation of this Queue is thread-safe.
(2022)
Here are Java Collections Interview Questions for fresher as well as experienced candidates to get their
dream job.
1) What is framework in Java?
A framework is a popular and readymade architecture that contains a set of classes and interfaces.
2) What is the Collection framework in Java?
Collection Framework is a grouping of classes and interfaces that is used to store and manage the objects.
It provides various classes like Vector, ArrayList, HashSet, Stack, etc. Java Collection framework can also
be used for interfaces like Queue, Set, List, etc.
3) Explain Collections Class
java.util.Collections is a class consists of static methods that operate on collections. It contains polymorphic
algorithms to operate on collections, “wrappers”. This class contains methods for algorithms, like binary
sorting, search, shuffling, etc.
,4) What is the hashCode()?
The hashCode() is a method that returns an integer hash code.
EXPLORE MORE Learn Java Programming with Beginners Tutorial08:32 Linux Tutorial for
Beginners: Introduction to Linux Operating...01:35 What is Integration Testing Software Testing
Tutorial03:04 What is JVM (Java Virtual Machine) with Architecture JAVA...02:24 How to write a
TEST CASE Software Testing Tutorial01:08 Seven Testing Principles Software Testing05:01 Linux
File Permissions Commands with Examples13:29 How to use Text tool in Photoshop CC Tutorial08:32
What is NoSQL Database Tutorial02:00 Important Linux Commands for Beginners Linux
Tutorial15:03
5) Distinguish between ArrayList and Vector in the Java collection framework.
ArrayList Vector
ArrayList is cannot be synchronized. Vector can be is synchronized.
It is not a legacy class. It is a legacy class.
It can increase its size by 50% of the size of the array. It can increase its size by doubling the size of the array.
ArrayList is not thread-safe. Vector is a thread-safe.
6) What is ArrayList in Java?
ArrayList is a data structure that can be stretched to accommodate additional elements within itself and
shrink back to a smaller size when elements are removed. It is a very important data structure useful in
handling the dynamic behavior of elements.
, 7) Differentiate between Iterator and ListIterator
The difference between Iterator and ListIterator is:
Iterator ListIterator
The Iterator can traverse the array elements in the ListIterator can traverse the array elements in backward as well as
forward direction. forward directions.
It can be used in Queue, List, and Set. It can be used in List.
It can perform add, remove, and set operation while traversing the
It can perform only remove operation.
collection.
8) What is the difference between Iterator and Enumeration?
The difference between Iterator and Enumeration
Iterator Enumeration
The Iterator can traverse both legacies as well as non-legacy
Enumeration can traverse only legacy elements.
elements.
The Iterator is fail-fast. Enumeration is not fail-fast.
The Iterator is very slow compare to Enumeration. Enumeration is fast compare to Iterator.
The Iterator can perform remove operation while traversing the The Enumeration can perform only traverse operation on the
collection. collection.
9) Define BlockingQueue
BlockingQueue is an interface used in Java that can extend the Queue. It provides concurrency in various
queue operations like retrieval, insertion, deletion, etc.
The Queue waits to become non-empty at the time of retrieving any elements. BlockingQueue should not
contain null elements. The implementation of this Queue is thread-safe.
