Interview Questions On Collections Java
Interview Questions on Java Collections
Interview Questions On Collections Java
During a Java interview focusing on collections, you can expect questions related to different types of collections interfaces and classes, their methods, when to use each type of collection, performance considerations, and common usage scenarios. Interviewers may also ask about specific classes like ArrayList, HashMap, LinkedList, and TreeSet, differences between them, and when to use one over the other based on requirements. Additionally, you might be asked about iteration techniques, sorting, searching, and how to handle concurrent modification exceptions. Having a solid understanding of collections framework in Java along with practical examples and knowledge of collection-related algorithms and complexities will greatly benefit you during the interview.
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1 - What are the different types of collections in Java?
The different types of collections in Java include List, Set, Map, and Queue. List is an ordered collection that allows duplicate elements, Set is a collection that does not allow duplicates, Map is a collection of key value pairs, and Queue is a collection used to hold multiple elements prior to processing.
2) What is the difference between ArrayList and LinkedList?
ArrayList is implemented as a resizable array, while LinkedList is implemented as a doubly linked list. ArrayList provides constant time access to elements through its index, while LinkedList provides constant time access to elements only if you have a reference to the node.
3) How does HashMap work in Java?
HashMap in Java works based on hashing principle. It uses the hashCode() method of the keys to store and retrieve key value pairs efficiently. When a key value pair is put into a HashMap, the key's hash code is used to determine the index at which the value will be stored.
4) Explain the concept of iteration in Java collections.
Iteration in Java collections refers to the process of accessing each element in a collection sequentially. This can be achieved using iterators or enhanced for loop in Java. Iterating through a collection allows you to perform operations on each element stored in the collection.
5) What is the difference between HashSet and TreeSet?
HashSet in Java is an unordered collection that does not allow duplicate elements, while TreeSet is a sorted collection that does not allow duplicates. HashSet uses hashing to store elements, while TreeSet uses a sorted tree structure based on the natural ordering of elements or a custom Comparator.
6) How does ConcurrentHashMap differ from HashMap in Java?
ConcurrentHashMap in Java is a thread safe version of HashMap that allows concurrent access by multiple threads without the need for external synchronization. It achieves this by dividing the map into segments that can be locked independently, allowing multiple threads to read and write concurrently.HashMap, on the other hand, is not thread safe and can lead to ConcurrentModificationException if accessed by multiple threads simultaneously without proper synchronization.
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