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Interview Questions and Answers for 'BlackRock' - 9 question(s) found - Order By Newest | ||||
Frequently asked in all types of companies especially Indian Services companies. Frequently asked in CTS (Based on 2 feedback) | ||||
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Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. The value received from hashcode() is used as bucket number for storing elements. This bucket number is the address of the element inside the set/map. when you do contains() then it will take the hashcode of the element, then look for the bucket where hashcode points to and if more than 1 element is found in the same bucket (multiple objects can have the same hashcode) then it uses the equals() method to evaluate if object are equal, and then decide if contain() is true or false, or decide if element could be added in the set or not. | ||||
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Like Discuss Correct / Improve  java   collections   hashcode   advanced  hashtable Asked in 33 Companies intermediate   frequent | ||||
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Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM. | ||||
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Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached. | ||||
Sample Code for volatile | ||||
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Like Discuss Correct / Improve  java   oops   synchronization   volatile   java keywords Asked in 42 Companies intermediate   frequent | ||||
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Very frequently asked. Usually asked in different variants like Diff between StringBuffer , String Builder ; Difference between StringBuilder and String class; Choice between these classes etc. | ||||
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Ans. A string buffer implements a mutable sequence of characters. A string buffer is like a String, but can be modified. At any point in time it contains some particular sequence of characters, but the length and content of the sequence can be changed through certain method calls. The String class represents character strings. All string literals in Java programs, such as "abc" are constant and implemented as instances of this class; their values cannot be changed after they are created. | ||||
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Like Discuss Correct / Improve  java   string   stringbuffer   frequently asked Asked in 18 Companies basic   frequent | ||||
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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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Like Discuss Correct / Improve  java   collections   hashmap   map   concurrenthashmap   concurrenthashmap  concurrency   general electric   ge Asked in 32 Companies   rare | ||||
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Ans. class A { void test() { System.out.println("test() method"); } } class B { void test() { System.out.println("test() method"); } } Suppose if Java allows multiple inheritance like this, class C extends A, B { } A and B test() methods are inheriting to C class. So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity. | ||||
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Like Discuss Correct / Improve  multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem Asked in 20 Companies basic   frequent | ||||
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Ans. The goal of a synchronised block is to achieve mutual exclusion i.e at one time, the segment of the code should be executed by single thread only and hence the lock needs to be retrieved before executing the segment and then released. | ||||
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Like Discuss Correct / Improve  synchronized block   synchronized   synchronization   multithreading   threads   mutual exclusion   concurrency Asked in 4 Companies intermediate   frequent | ||||
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Ans. There was no multiple inheritance in java before version 8 as implementing multiple interfaces cannot be termed as inheritance. With Java 8 , came the concept of default methods wherein the class implementing the interface carries the default implementation from the interface and hence facilitating multiple inheritance. | ||||
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Like Discuss Correct / Improve  multiple inheritance  object oriented programming (oops)  oops concepts   inheritance  object oriented programming (oops)  oops concepts   oops concept Asked in 10 Companies   frequent | ||||
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Ans. https://www.redhat.com/archives/rhl-list/2005-April/msg04167.html | ||||
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Like Discuss Correct / Improve  unix  change default kernel Asked in 1 Companies | ||||
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Ans. HashTable locks the complete collection to provide synchronization whereas ConcurrentHashMap only locks segments to achieve synchronization and hence better efficient and faster. | ||||
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Like Discuss Correct / Improve  concurrentHashMap  HashTable  Map  Collections Asked in 2 Companies | ||||