Interview Questions and Answers for 'Java' | Search Interview Question

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Q41. Have you had to work with memory leak problems in javascript ?

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Q42. Write a method to track every click on a page.

JavaScript

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Q43. What is the difference between inheritance in PHP vs. Javascript?

JavaScript

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Q44. Write a Program to draw a fish ?

Core Java

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Q45. Should we do anything to avoid memory leaks in Java ?

Core Java

Ans. Java has a intrinsic way of checking leaks and reclaiming memory called garbage collection. Moreover Java doesn't support pointer arithmetics , so there is very low comparative chance of memory leaks, compared to C,C++

Though there may be tools that may audit code to make sure that we are not leaving much for the garbage collection to work but I have never heard anyone doing anything for memory leaks in Java.

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Q46. Explain Collections in Java

Core Java

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Q47. Is String mutable or immutable in Java ?

Core Java

Ans. String is Immutable because of String Constant Pool.

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Q48. What are different types of Polymorphism in Java ?

Core Java

Ans. run time polymorphism
compile time polymorphism

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Q49. Can we assign the reference to this variable ?

Core Java

Ans. No

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Q50. Hash map using/without using Java 8

Core Java

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Q51. What is Throwable ?

Core Java

Ans. Throwable in java is a class that is the superclass of all exceptions and errors which may occurs in java program.It extends obcect class.

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Q52. What is Defer Parsing JavaScript ?

JavaScript

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Q53. What is string pool and what is the use of intern() function ?

Core Java

Ans. The Java String class intern() method returns the interned string. It returns the canonical representation of string.

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Q54. How to make a collection thread safe?

Core Java

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Q55. What is a comparator ?

Core Java

Ans. Java Comparator compares two Java objects in a “compare(Object 01, Object 02)” format. Using configurable methods, Java Comparator can compare objects to return an integer based on a positive, equal or negative comparison

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Q56. Why should we go for custom defined exceptions even if we have many exceptions provided already using throw keyword

Core Java

Ans. It gives us the liberty to throw the specific exceptions which are required and also we can control the handling of exceptions

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Q57. How does Garbage Collector work? What are the realizations of Garbage Collector.

Core Java

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Q58. How multiple catch block works ?

Core Java

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Q59. What is the use of toString method ?

Core Java

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Q60. Class and Object methods.

Core Java

Ans. class:- A class describe the contents of an object, an it describe the detail of data field called instance variable and defines the operations called method.

Object:-An object is an element of a class. Object have the behaviors of their class.

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Q61. How to get collections from a Stream

Core Java

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Q62. Can anonymous class implement interface and extend a class

Core Java

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Q63. What is ServerSocket in Java ?

Core Java

Ans. This class implements server sockets. A server socket waits for requests to come in over the network. It performs some operation based on that request, and then possibly returns a result to the requester.

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Q64. What are the distinguished qualities in Java that no other language possess ?

Core Java

Ans. Java is widely adopted as an enterprise standard technology across business domains and technical domains ( Web , Desktop , mobile , data science etc ) and has a vast ecosystem of frameworks and libraries.

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Q65. What is headless mode in Java ? Why is it used ?

Core Java

Ans. It’s a mode that can be used for creating Back end application without the front end UI.

The advantage is that it reduces the number of packages that needs to be loaded ( by ignoring ui packages )

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Q66. Write a code to detect the longest palindromic substring

Core Java

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Q67. What are the pros and cons of Lambda expressions ?

Core Java

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Q68. Write a program to rotate a matrix.

Core Java

Ans. public class Matrix {

   public static void main(String[] args) {
      int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
      };
      Matrix.rotateMatrix(matrix);
      for (int i = 0; i < matrix.length; i ){
         for (int j = 0; j < matrix.length; j ){
            System.out.print(matrix[i][j] " ");
         }
         System.out.println();
      }
   }

   public static void rotateMatrix(int[][] matrix){
      int row = matrix.length;
      //first find the transpose of the matrix.
      for (int i = 0; i < row; i ){
         for (int j = i; j < row; j ){
            int temp = matrix[i][j];
            matrix[i][j] = matrix[j][i];
            matrix[j][i] = temp;
         }
      }
      //reverse each row
      for (int i = 0; i< row; i ){
         for(int j = 0; j< row/2; j ){
            int temp = matrix[i][j];
            matrix[i][j] = matrix[i][row - 1 - j];
            matrix[i][row - 1 - j] = temp;
         }
      }

   }

}

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Q69. How does hashmap works ?

Core Java

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Q70. How do you achieve String immutability ?

Core Java

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