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Q41. Is there a way to know size of an object in Java ?

Ans. No, Java doesn't have a sizeOf operator. In C / C++ , its required to determine how much memory allocation is required which is not the case with Java. Java handles memory allocation and deallocation intrinsically.

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Q42. What are the cursors available in Java ?

Core Java

Ans. Enumeration
Iterator
List iterator

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Q43. Explain dot(.) operator ?

Core Java

Ans. Its used to access the object properties using the object reference or class properties using the Class Name. Moreover its used to access the classes and Interfaces of a package.

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Q44. What are the different operators in Java ?

Core Java

Ans. && - AND
|| - OR
! - LOGICAL NOT

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Q45. What is the difference between && and & in Java ?

Core Java

Ans. && is a Logical whereas & is a bitwise operator

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Q46. What are the core OOPs concepts ?

Core Java

Ans. Abstraction, Encapsulation, Polymorphism , Composition and Inheritance

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Q47. Where do you see yourself in next 5 years?

General

Ans. Sample Answers -

Getting better with upcoming technologies and be a Lead developer.

In accordance with the company, working as a permenant employee.

Be an associate architect.

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Q48. What is the precedence of operators in Java ?

Core Java

Ans. http://introcs.cs.princeton.edu/java/11precedence/

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Q49. What is a mutator in Java?

Core Java

Ans. Mutator is another name for setter methods, i.e the method allows for mutating the property of an object and eventually the state of the object.

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Q50. Why do we need Garbage collection ?

Core Java

Ans. Garbage collection mechanism frees up the memory that is no longer needed. In languages like C / C++ the deallocation needs to be done explicitly by the programmer and hence any leniency may result in memory leak. Garbage collection in java ensures that all unused memory is reclaimed and hence there are no memory leaks.Moreover it relieves the programmer from the hassle of carefully releasing all memory.

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Q51. Explain OOPS.

Core Java

^{This question was recently asked at 'Acute Informatics,General Atomics'.This question is still unanswered. Can you please provide an answer.}

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Q52. What is the difference between Enumeration and Iterator ?

Core Java

Ans. Enumeration can iterate only legacy collections like Vector , HashTable and Stack whereas Iterator can iterate both legacy and non legacy collections.

Enumeration is less safer than Iterator

Enumeration is fail safe whereas Iterator is fail fast

Iterator allows for removal of element while traversal whereas Enumeration doesn't have remove method.

Enumerations were introduced in Java 1 whereas Iterators were introduced with Java 2

Enumerations have methods like hasMoreElements and nextElement whereas Iterators have methods like hasNext, next and remove

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Q53. Which of the following is valid greater than and equal to operator in Java ?

>=
=>

Core Java

Ans. >=

=> will result in error.

=> somewhat looks like lambda operator "->"

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Q54. What is a ternary operator ?

Database

Ans. Ternary operator , also called conditional operator is used to decide which value to assign to a variable based on a Boolean value evaluation. It is used as

condition ? value1 : value2

For example

int y = (x > 0) ? x:0; // assign x if it's greater than 0, else assign 0

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Q55. Why doesn't java support operator overloading ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

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Q56. How can i split a linked list in two parts in java 8?

Core Java

Ans. This can be done using a Spliterator.

LinkedList list = Arrays.asList("names","numbs","birds","animals");
Spliterator split1 = list.Spliterator();
Spliterator split2 = split1.Spliterator();

Now, the LinkedList is split into split1 and split2.
use split2 first then split1 to check the output.

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Q57. Explain OOps concepts.

Core Java

Ans. There are four main OOP concepts in Java. These are:

Abstraction. Abstraction means using simple things to represent complexity. We all know how to turn the TV on, but we don?t need to know how it works in order to enjoy it. In Java, abstraction means simple things like objects, classes, and variables represent more complex underlying code and data. This is important because it lets avoid repeating the same work multiple times.

Encapsulation. This is the practice of keeping fields within a class private, then providing access to them via public methods. It?s a protective barrier that keeps the data and code safe within the class itself. This way, we can re-use objects like code components or variables without allowing open access to the data system-wide.

Inheritance. This is a special feature of Object Oriented Programming in Java. It lets programmers create new classes that share some of the attributes of existing classes. This lets us build on previous work without reinventing the wheel.

Polymorphism. This Java OOP concept lets programmers use the same word to mean different things in different contexts. One form of polymorphism in Java is method overloading. That?s when different meanings are implied by the code itself. The other form is method overriding. That?s when the different meanings are implied by the values of the supplied variables. See more on this below.

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Q58. Can we modify a list while iterating it ?

Core Java

Ans. No,we cannot.I t will give concurrentModificationExceptin error. It can be resolved by using ConcurrentClasses like ConcurrentHashMap,CopyOnWriteArrayList,BlockingQueue etc which are fail-safe and wont give exception.

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Q59. Design ATM machine application using oops.

Design

^{This question was recently asked at 'Atos'.This question is still unanswered. Can you please provide an answer.}

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Q60. What is garbage collection ?

Core Java

Ans. The garbage collection is a facility wherein a program runs on the Java Virtual Machine which gets rid of objects, which are not being used by a Java application anymore. It is a form of automatic memory management and recollection.

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Q61. What is the access time for ArrayList and LinkedList ?

Data Structure

Ans. O(1) for ArrayList
O(n) for LinkedList

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Q62. Difference between == and === ?

JavaScript

Ans. == compares values === is used in scripting languages for comparing two values as well as there data tpe. like in js,php.

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Q63. How to sort objects based on one of the field ?

Core Java

Ans. Using comparable and comparator and sorted collections like TreeSet or TreeMap.

or

use stream api from java 8 onwards which internally refers to comparable and comparator through lambda expressions

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Q64. Where to use interface and abstract class ?

Core Java

^{This question was recently asked at 'Exterro,Equator Business Solutions'.This question is still unanswered. Can you please provide an answer.}

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Q65. What is the name of DNS service provided by AWS ?

Amazon Web Services (AWS)

Ans. Route 53

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Q66. Difference between Route53 aliasis and cname ?

Amazon Web Services (AWS)

Ans. Cname doesn't support naked domain names whereas aliasis does.

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Q67. How to write an iterator for an iterator of iterators?

Core Java

Ans. CustomArrayList myarrayList = new CustomArrayList();
      myarrayList.add("Value 1");
      myarrayList.add("Value 2");
      myarrayList.add("Value 3");

      for (String string : myarrayList) {
         System.out.println(string);
      }

package sample.utils;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class CustomArrayList implements Iterable {

   private ArrayList mylist = new ArrayList();

   public void add(T t) {
      this.mylist.add(t);
   }

   @Override
   public Iterator iterator() {
      return new CustomIterator(mylist);
   }

   class CustomIterator implements Iterator {

      private int indexPosition = 0;
      private List internalList;

      public CustomIterator(List internalList) {
         this.internalList = internalList;
      }

      @Override
      public boolean hasNext() {
         if (internalList.size() >= indexPosition 1) {
            return true;
         }
         return false;
      }

      @Override
      public E next() {
         E val = internalList.get(indexPosition);
         indexPosition ;
         return val;
      }

   }

}

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Q68. How many heaps will be there with 3 threads ?

Core Java

Ans. All threads share a common heap.

Each thread has a private stack, which it can quickly add and remove items from. This makes stack based memory fast, but if you use too much stack memory, as occurs in infinite recursion, you will get a stack overflow.

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Q69. What is SNMP ?

Networking

Ans. SNMP or Simple Network Management protocol is an application layer protocol for exchanging management information between network devices.

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Q70. Which of the following is true for == operator ?

Core Java

a. For primitives, == checks if the variables on left and right have same data type

b. For primitives, == checks if the variables on left and right have same value

c. For Objects, == checks if the references on left and right have same data type

d. For Objects, == checks if the references on left and right have same value

Ans.b. For primitives, == checks if the variables on left and right have same value

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