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 Advanced level question. Frequently asked in High end product companies. Frequently asked in Google , Cognizant and Deloitte ( Based on 2 feedback ) | ||||
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| 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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 Discuss Correct / Improve  java oops string string class immutable immutability advanced  Asked in 39 Companies  expert  frequent | ||||
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| Usually asked only to fresh graduates and less experienced developers. | ||||
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| Ans. These are threads that normally run at a low priority and provide a basic service to a program or programs when activity on a machine is reduced. garbage collector thread is daemon thread. | ||||
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| Discuss Correct / Improve java threads multi threading operating system daemon thread garbage collection Asked in 10 Companies intermediate frequent | ||||
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| Ans. Its the process of creating Java Objects out of XML structures. | ||||
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| Discuss Correct / Improve xml java api for xml unmarshalling parser sax dom architecture Asked in 1 Companies | ||||
| Advanced level question usually asked to senior developers , leads and architects. | ||||
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| Ans. Volatile is an instruction that the variables can be accessed by multiple threads and hence shouldn't be cached. As volatile variables are never cached and hence their retrieval cannot be optimized. | ||||
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| Ans. public static void main(String ar[]) { int n=5; if((n/2)*2==n) { System.out.println("Even Number "); } else { System.out.println("Odd Number "); } } | ||||
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| 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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| Discuss Correct / Improve java collections hashmap map concurrenthashmap concurrenthashmap concurrency general electric ge Asked in 32 Companies rare | ||||
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Which of the following class creates mutable objects ?
