Interview Questions and Answers for 'Map' | Search Interview Question

Interview Questions and Answers - Order By Newest

Q61. Isnt the use of HashTable and ConcurrentHashMap the same, i.e providing synchronized map collection ?

Ans. Both provide the thread safety but the actual difference come when talk about performance. CHM gives best performance when no of writer threads are less in number.

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Q62. How many read and write operations are provided at the same time by ConcurrentHashMaps ?

Core Java

Ans. ConcurrentHashMaps provide unlimited read operation fro multi threaded environment. For write operation only one thread can change value for particular segment of map.

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Q63. Explain different inheritance mapping strategies with JPA / Hibernate.

Hibernate

Ans. table per hierarchy
table per concrete class
table per sub class

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Q64. Is HashMap Synchronized ?

Core Java

Ans. No HashMap isn't synchronized. ConcurrentHashMap and Hashtable are synchronized.

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Q65. Is ConcurrentHashMap synchronized ?

Core Java

Ans. Yes, ConcurrentHashMap is synchronized.

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Q66. Difference between TreeMap and SortedMap ?

Core Java

Ans. sortedMap is an interface ,while TreeMap is an implementation of sortMap.

We can not create an instance of sortedMap but we can create an instance of treeMap

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Q67. Difference between HashMap and Dictionary in Java ?

Core Java

Ans. HashMap implements the Map interface while the Dictionary does not.

HashMap was introduced after HashTable and Dictionary.

Dictionary is currently obsolete in java.

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