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Core java - Interview Questions and Answers for 'Efi' - 6 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 )
  Q1. Difference between == and .equals() ?Core Java
Anonymous
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     Asked in 289 Companies      basic        frequent

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 Q2. What things should be kept in mind while creating your own exceptions in Java?Core Java
Admin
info@buggybread.com
Ans. All exceptions must be a child of Throwable.

If you want to write a checked exception that is automatically enforced by the Handle or Declare Rule, you need to extend the Exception class.

You want to write a runtime exception, you need to extend the RuntimeException class.

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   Like         Discuss         Correct / Improve     java   exceptions   exception handling   user defined exceptions   throwable   architecture   library development   technical architect   technical lead


 Q3. What are the benefits of using Wrapper classes over primitive types ?Core Java2017-08-24 21:35:53

Ans. With Collection classes , we cannot use primitive types. Moreover for any class using generic types, we cannot use primitive types.

They add more functionality by means of additional methods.

As their reference can be null , they offer consistent check for uninitialized state.

They facilitate caching and reuse by means of constant Pools.

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   Like         Discuss         Correct / Improve     wrapper classes  benefits of wrapper classes over primitives


Frequently asked in high end product companies.
 Q4. Write code for LRU CacheCore Java2017-01-10 10:15:17

Ans. https://www.geeksforgeeks.org/lru-cache-implementation/

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   Like         Discuss         Correct / Improve     cache  LRU cache  coding  code     Asked in 10 Companies      intermediate


  Q5. What are the core OOPs concepts ?Core Java2017-02-06 16:15:55

Ans. Abstraction, Encapsulation, Polymorphism , Composition and Inheritance

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   Like         Discuss         Correct / Improve     core oops concepts     Asked in 65 Companies      basic        frequent


 Q6. What are the benefits of immutability or Immutable classes ?Core Java2017-08-28 19:36:18

Ans. Immutable objects are thread-safe so you will not have any synchronization issues.Immutable objects are good for Map keys and Set elements, since these typically do not change once created.Immutability makes it easier to write, use and reason about the code (class invariant is established once and then unchanged)Immutability makes it easier to parallelize your program as there are no conflicts among objects.The internal state of your program will be consistent even if you have exceptions.References to immutable objects can be cached as they are not going to change.

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   Like         Discuss         Correct / Improve     immutable  immutability classes   benefits of immutable  immutability classes     Asked in 1 Companies




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