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Interview Questions and Answers for 'Redis' - 19 question(s) found - Order By Newest | ||||
Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback ) and Epam Systems | ||||
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Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory. x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object. Sample code: String x = new String("str"); String y = new String("str"); System.out.println(x == y); // prints false System.out.println(x.equals(y)); // prints true | ||||
Sample Code for equals | ||||
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Like Discuss Correct / Improve  java   string comparison   string   object class   ==   equals   object equality  operator   == vs equals   equals vs == Asked in 294 Companies basic   frequent | ||||
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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. | ||||
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Ans. Underlying data structure for ArrayList is Array whereas LinkedList is the linked list and hence have following differences - 1. ArrayList needs continuous memory locations and hence need to be moved to a bigger space if new elements are to be added to a filled array which is not required for LinkedList. 2. Removal and Insertion at specific place in ArrayList requires moving all elements and hence leads to O(n) insertions and removal whereas its constant O(1) for LinkedList. 3. Random access using index in ArrayList is faster than LinkedList which requires traversing the complete list through references. 4. Though Linear Search takes Similar Time for both, Binary Search using LinkedList requires creating new Model called Binary Search Tree which is slower but offers constant time insertion and deletion. 5. For a set of integers you want to sort using quicksort, it's probably faster to use an array; for a set of large structures you want to sort using selection sort, a linked list will be faster. | ||||
Sample Code for ArrayList Sample Code for LinkedList | ||||
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Like Discuss Correct / Improve  collections   java   data structures   arraylist   linkedlist   arraylist vs linkedlist Asked in 61 Companies Basic   frequent | ||||
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Basic and Very Frequently asked. | ||||
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Ans. Polymorphism means the condition of occurring in several different forms. Polymorphism in Java is achieved in two manners 1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas 2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding. | ||||
Sample Code for overloading Sample Code for overriding | ||||
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Like Discuss Correct / Improve  polymorphism  object oriented programming (oops)  oops concepts  oops concepts Asked in 108 Companies Basic   frequent | ||||
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Ans. Predicate represents an anonymous function that accepts one argument and produces a result. Supplier represents an anonymous function that accepts no argument and produces a result. Consumer represents an anonymous function that accepts an argument and produces no result. | ||||
Sample Code for Predicate Sample Code for Supplier Sample Code for Consumer | ||||
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Like Discuss Correct / Improve  java   java8   predicate   consumer   supplier   lambda expression   predicate vs consumer vs supplier expert | ||||
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Ans. Java doesn't support multiple inheritance. Interfaces does't facilitate inheritance and hence implementation of multiple interfaces doesn't make multiple inheritance. | ||||
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Like Discuss Correct / Improve  java   oop   oop concepts   inheritence   multiple inheritence   basic interview question Asked in 10 Companies basic   frequent | ||||
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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 memory pool containing all the reflective data of the java virtual machine itself, such as class and method objects. With Java VMs that use class data sharing, this generation is divided into read-only and read-write areas. The Permanent generation contains metadata required by the JVM to describe the classes and methods used in the application. The permanent generation is populated by the JVM at runtime based on classes in use by the application. In addition, Java SE library classes and methods may be stored here. | ||||
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Like Discuss Correct / Improve  java   jvm   memory management   permgen   permanent generation   advanced   architecture Asked in 9 Companies expert | ||||
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Ans. DEBUG ERROR ALL WARN INFO FATAL OFF TRACE TRACE_INT WARN | ||||
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Like Discuss Correct / Improve  java   log4j   log4j level   logging   error logging Asked in 10 Companies | ||||
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Ans. log4j is by apache while java logging api is given by sun. log4j is more powerful,extensible and simple to use than java logging api. | ||||
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Ans. This collections class has been implemented in such a manner that it can never throw ConcurrentModificationException. As it performs update and write operations by creating a new copy of ArrayList, It's slower compared to ArrayList. | ||||
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Like Discuss Correct / Improve  java   collections   list   arraylist   copyonwritearraylist   advantages-disadvantages   ConcurrentModificationException Asked in 4 Companies Expert | ||||
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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. A dirty read occurs when a transaction is allowed to read data from a row that has been modified by another running transaction but not yet committed. | ||||
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Like Discuss Correct / Improve  database transaction Asked in 8 Companies | ||||
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Ans. Redis is an in-memory data structure store, used as a database, cache and message broker. | ||||
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Like Discuss Correct / Improve  redis | ||||
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Ans. Asynchronous Replication of information from master to all slaves. Redis is an in memory storage and hence any crash may result in complete loss of information on a cluster. | ||||
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Like Discuss Correct / Improve  Redis  replication in redis Asked in 1 Companies | ||||
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Ans. Oracle is a relational database. Cassandra is a noSQL Database whereas Redis is an inmemory cache. | ||||
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Like Discuss Correct / Improve  oracle  casandra  redis | ||||
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Ans. HGETALL <key> | ||||
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Like Discuss Correct / Improve  Redis  check fields and value for a key | ||||
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Ans. We can either do DBSIZE or KEYS * Keys * will return the list of all keys too so DBSIZE is preferred if we just want the count. | ||||
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Like Discuss Correct / Improve  Redis  Count All Keys  DBSIZE  Keys * | ||||
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Ans. SET <KEY_NAME> <VALUE> | ||||
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Like Discuss Correct / Improve  redis  setting a key | ||||
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This question is still unanswered. Can you please provide an answer. | ||||
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Like Discuss Correct / Improve  Amazon Web Services (AWS)  Redis  Memcache | ||||