Java Interview Questions and Answers on HashMap

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This session helpful for the candidates preparing for the Core java interview. In this session, I explained java interview questions and answers for Map Implementations(HashMap, LinkedHashMap, TreeMap, ConcurrentHashMap, Collections.synchronizedHashMap, WeakHashMap) and when to use which map Implemenations with Examples.

[@deepak123417]

Please describe load factor and issues with re hashing and how it can be resolved in details

[@priyaal8153]

Sir your explaination is crystal clear.. I watched so many videos it was too confused I thought no one can make me understand this concept.. Bt I'm wrong you broke that.. Hats off sir..

[@SivaReddyJavaTechie]

Thanks Priya. Please refer our KZbin channel to your friends circle as it might be helpful for them. Happy learning.

[@rajanpunniamoorthy3452]

Well presented about HashMap. Good work Reddy.

[@SivaReddyJavaTechie]

Thanks Rajan. Please share our KZbin Channel with your friends and colleagues as it may be helpful for them. Happy Learning.

[@SuprajaYKM]

In concurrent hashmap suppose one segment is locked for writing data, and user is accessing data from concurrent hashmap at same time then will user loose data from locked segment.

[@maheshreddy9351]

Hi sir, If we add one entry to hashMap,On which basis it will be inserted into bucket i mean how it choose the particular index. Thanks in advance.

[@ankittiwary3712]

sir please upload tutorial on contract between equals and hashcode method with example

[@pratikshajadhav7297]

Can you please explain collision concept and handling in HashMap

[@sandeepmankena363]

thank bro

[@abhishekcooldude100]

Hi Sir, its been an excellent session for interview questions, however can you upload tutorials for spring interview questions for experienced professionals too.

[@SivaReddyJavaTechie]

Hi Abhishek, You can find spring related Interview Q&A @ kzbin.info/www/bejne/hXmbhJyCjc6ChM0. You can go through our KZbin channel playlists, you will find more useful videos on various topics for interviews. Please refer our KZbin channel to your friends circle as it might be helpful for them. Happy Learning.

[@princeverma4938]

Can we use custom object as a key of hadhmap

[@SivaReddyJavaTechie]

Hi Prince, Yes we can use custom object as a key to HashMap but you need to override the hashcode and equals methods.

[@RoopkishorPandeyji]

Hi Sir, I am looking for internal implementation of Hashmap, can u please explain. provide link if you already have release the video.

[@SivaReddyJavaTechie]

kzbin.info/www/bejne/r4qXloytr619aas

[@RoopkishorPandeyji]

thank you shiva but i was looking for explanation of internal implementation of get put and remove methods. what to write inside put if i have to write my own put method

[@unbiased-review]

Very well explained sir

[@SivaReddyJavaTechie]

Thanks.

[@shivanaikrachanaikar2843]

Hi , Hashmap is accepting the 2 null values but you said it will allow only one null value so please clarify

[@SivaReddyJavaTechie]

HashMap allows only one null value as key. Even though you add multiple null values as keys, it will override the early null key value and when you print the hashMap you will see only one key with null value in the HashMap.

[@melodyjunction6908]

Hi..sir can assign same value for multiple keys?

[@amitdeshmukh266]

sanmati ayatawad, yes can assign same value to multiple keys

[@SivaReddyJavaTechie]

You can assign mutile null values but it will accept only one null value as a key

[@monissiddiqui1529]

Hashmap custom value if put then how it work

[@SivaReddyJavaTechie]

If you want to add custom value then you need to override equals and hashcode in class. Hashmap works based on your custom logic for equals and hashcode when you add custom (user defined object) as key.

[@monissiddiqui1529]

@@SivaReddyJavaTechie sir can u give any example today interviewer had ask me this quest in Accenture