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Core java - Interview Questions and Answers for 'Prokarma' - 3 question(s) found - Order By Newest

Advanced level question. Frequently asked in High end product companies. Frequently asked in Cognizant and Deloitte ( Based on 2 feedback )
  Q1. Why is String immutable in Java ?Core Java
Anonymous
Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references.

Example -

String str1 = "String1";
String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool

// Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too

2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached.

3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment.

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Related Questions

 How does making string as immutable helps with securing information ? How does String Pool pose a security threat ?
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  Q2. Can we have null keys in TreeMap ?Core Java
Admin
info@buggybread.com
Ans. No, results in exception.

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Related Questions

  Difference between TreeMap and HashMap ?
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a. Set
b. List
c. Map
d. Any Collection implementation
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a. HashMap
b. TreeMap
c. LinkedHashMap
d. LinkedMap
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  Difference between Map and HashMap ?


 Q3. What is a ConcurrentHashMap ?Core Java
Admin
info@buggybread.com
Ans. ConcurrentHashMap is a hashMap that allows concurrent modifications from multiple threads as there can be multiple locks on the same hashmap.

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Related Questions

  What is ConcurrentLinkedDeque ?
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 isnt the use of HashTable and ConcurrentHashMap the same, i.e providing synchronized map collection ?
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