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Q1021. In the following code, which text will get printed immediately after Hello

for(int countx=0;countx<10;count++){
System.out.println("World");
for(int countx=0;countx<10;count++){
System.out.println("Friend");
for(int countx=0;countx<10;count++){
System.out.println("Hello");
break;
}
System.out.println("Buddy");
}
}

Core Java

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

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_{Like Discuss Correct / Improve break statement}

Q1022. As root, if you have to assign the owner for the file and set only read permission for the owner, Write a unix command to do it.

Unix

Ans. chmod 477

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Q1023. What do we mean by a Data Type ?

Core Java

Ans. if you have similar type of data or objects or entities, then we can give them a type with unique name. And this name will be our Data type.

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Q1024. Why shouldn't we use string concatenation extensively or in a loop ?

Core Java

Ans. Because String being an immutable object creates a new object upon each concatenation cycle. If there is any such need , we should use String Builder whose objects are mutable.

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Q1025. How is string object immutable if we can concat a string to it ?

Core Java

Ans. Because it doesn't make the change in the existing string but would create a new string by concatenating the new string to previous string. So Original string won't get changed but a new string will be created. That is why when we say

str1.concat("Hello");

It means nothing because we haven't specified the reference to the new string and we have no way to access the new concatenated string. Accessing str1 with the above code will still give the original string.

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Q1026. Does Wrapper classes produces immutable objects ?

Core Java

Ans. Yes

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Q1027. Is dependency injection possible if we don't have inheritance / Composition ?

Design

Ans. Without composition - No, as it's the core of dependency injection.

With Inheritance - Yes, through interface implementation.

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Q1028. Is Runtime Polymorphism possible without Inheritance ?

Core Java

Ans. Yes, Runtime Polymprohism requires either Class inheritance or Interface implementation.

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_{Like Discuss Correct / Improve runtime polymorphism object oriented programming (oops) oops concepts method overriding inheritance object oriented programming (oops) oops concepts}

Q1029. Which of the OOP's features facilitate dependency injection ?

Design

Ans. Inheritance , Runtime Polymorphism and Composition.

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Q1030. Lets say we have a set "set1" with objects of Class A, Class has a non static string called element1, Write a code ( using lambda expression ) to see if there is any object in the set with element1 = "Hello".

Core Java

Ans. set1.stream().filter(p->p.element1.equals("Hello")).findAny().isPreent();

or

set1.stream().map(A::getElement1).anyMatch("Hello"::equals)

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Q1031. Let's suppose we have an to destroy objects, Design a program to implement garbage collection ?

Design

Ans. Step 1 - We can create a Registry Class having Map of all created objects as key and References list as value.

Step 2 - Whenever we create an object , we should update the Registry in the constructor to add the new object.

Step 3 - Whenever we assign a new reference to the object , we need to update the entry in Map. Similarly if the reference get's removed ( end of scope etc ), we need to remove the entry of reference from the list.

Step 4 - We can have threaded code to monitor the Map to see if any object looses all it's references and should call the method to destroy object and clean the memory.

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Q1032. How can we track of all objects created in an application ?

Design

Ans. We can store the references in a collection by adding to those objects in the collection. We can create a class "ObjectRegistry" with a collection or multiple collections with a search algorithm to look for the already collected objects.

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_{Like Discuss Correct / Improve objects}

Q1033. What are the disadvantages of Bean Auto Wiring in Spring ?

Spring

Ans. It can always be overridden with explicit wiring. Moreover it's confusing if we use both explicit as well as explicit wiring in the project.

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_{Like Discuss Correct / Improve Spring beans auto wiring autowiring}

Q1034. What are the uses of Abstraction ?

Core Java

Ans. Loose Coupling
Facilitates designing complex applications by making them modular.

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Q1035. What is ORM or Object Relationship Mapping ?

Database

Ans. ORM is the mapping technique, which maps object with relational data model. As we know that in java we need objects we can not user data in relational(in table form). So ORM is set of guideline which allows us to map relational data model in object form.

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_{Like Discuss Correct / Improve orm Asked in 1 Companies frequent}

Q1036. Explain Generics in Java ?

Core Java

Ans. Generics are a facility of generic programming that were added to the Java programming language in 2004 within J2SE5.0. They allow "a type or method to operate on objects of various types while providing compile-time type safety.

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_{Like Discuss Correct / Improve generics Asked in 7 Companies}

Q1037. How can we convert a character or a character array into a String ?

Core Java

Ans. String has an argument constructor that take char array as argument and creates a string.

There is no constructor available with String that takes in a character and creates a String. We can use StringBuilder which has a char argument constructor.

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_{Like Discuss Correct / Improve character char char array String char to String char array to String}

Q1038. How can we convert String into Char array and vice versa ?

Core Java

Ans. There is a method toCharArray() within String class that can be used to convert string to char array.

string.toCharArray();

String class has an argument constructor that takes a char array and create a string

new String(charArray);

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_{Like Discuss Correct / Improve string char array}

Q1039. In which memory segment - heap or stack, the following stored by JVM

1. static members
2. objects
3. object references
4. local or method variables

Core Java

Ans. static members are stored in method area of heap

objects are stored on heap

object references are stored on stack

local or method variables are stored on stack

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_{Like Discuss Correct / Improve jvm memory management stack heap}

Q1040. Why can't we have diamond problem with interfaces ?

Core Java

Ans. Interfaces don't have member elements and method definitions that could cause diamond problem. With Java 8, Interfaces have default method definitions. This could have created diamond problem but Java introduced a compile time check for "duplicate default methods" in case same method is derived from multiple interfaces and no definition is overridden by the class.

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Q1041. Why the following code produced this output ?

int x = 5;
int y = x;
y = 10;

System.out.println(x); // prints 5 and not 10

Core Java

Ans. Because when we say y = x, the value of x is copied to another memory location and then y points to that new memory location.

Unlike object references that once assigned point to same object in memory, value is copied in case of variable assignment.

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_{Like Discuss Correct / Improve variable assignment}

Q1042. What are ascii values for capital and lower case alphabets ?

Core Java

Ans. 65 to 90 for capital case alphabets

97 to 122 for lower case alphabets

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Q1043. How can we check if a particular character is upper case in Java ?

Core Java

Ans. 1. We can compare the ascii value of the character. Ascii for Capital case character is from 65 to 90.

2. We can compare to see if lowerCase of the character is not equal to character itself.

For example -

if character is 'a' the following code

new StringBuilder(char).toString().toLowerCase().equals(new StringBuilder(char)

will return true and hence char is lower case

if character is 'A' the following code

new StringBuilder(char).toString().toLowerCase().equals(new StringBuilder(char)

will return false and hence char is upper case

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_{Like Discuss Correct / Improve check upper case character character}

Q1044. How can we convert char into a String ?

Core Java

Ans. We can use StringBuilder. StringBuilder accepts char as the argument for it's constructor.

new StringBuilder('').toString();

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Q1045. Do we have a method to reverse a string in String class ?

Core Java

Ans. No but we have it in StringBuilder.

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Q1046. How to use spring boot to configure different datasources ?

Spring Boot

Ans. https://github.com/jahe/spring-boot-multiple-datasources

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Q1047. Write method to delete Node from a LinkedList.

Data Structure

Ans. public class LinkedList {

   Node start = null;
   Node head = null;

   class Node {
      Integer body;
      Node nextNode;

      Node(Integer value) {
         body = value;
      }
   }

   private void addNodeToEnd(Integer value) {
      if (start == null) {
         start = new Node(value);
         head = start;
         head.nextNode = null;
         return;
      }

      while (head.nextNode != null) {
         head = head.nextNode;
      }

      head.nextNode = new Node(value);
   }

   private void deleteNode(Integer value) {
      head = start;
      while (head.nextNode != null) {
         if(head.nextNode.body == value){
            head.nextNode = head.nextNode.nextNode;
         }

         head = head.nextNode;
      }
   }



   private void traverse() {
      head = start;
      while (head != null) {
         System.out.println(head.body);
         head = head.nextNode;
      }
   }

   public static void main(String[] args) {
      LinkedList ll = new LinkedList();

      ll.addNodeToEnd(5);
      ll.addNodeToEnd(10);
      ll.addNodeToEnd(15);

      ll.traverse();

      ll.deleteNode(10);

      ll.traverse();

   }
}

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Q1048. In a Linked list with sorted numbers, insert a new numbers while maintaining the sort order.

Algorithm

Ans.
public class LinkedList {

   Node start = null;
   Node head = null;

   class Node{
      Integer body;
      Node nextNode;

      Node(Integer value){
         body = value;
      }
   }

   private void insertInMiddle(Integer value){
      head = start;
      if(start == null) {
         start = new Node(value);
         head = start;
         head.nextNode = null;
         return;
      }

      while(head.body < value){
         if(head.nextNode == null || head.nextNode.body >= value){
            Node newNode = new Node(value);
            newNode.nextNode = head.nextNode;
            head.nextNode = newNode;

            break;
         }
         head = head.nextNode;
      }
   }

   private void traverse(){
      head = start;
      while(head != null){
         System.out.println(head.body);
         head = head.nextNode;
      }
   }

   public static void main(String[] args){
      LinkedList ll = new LinkedList();

      ll.insertInMiddle(5);
      ll.insertInMiddle(10);
      ll.insertInMiddle(15);
      ll.insertInMiddle(7);

      ll.traverse();

   }
}

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Q1049. Write a program for LinkedList, with method to append node and traversing the list ?

Algorithm

Ans. public class LinkedList {

   Node start = null;
   Node head = null;

   class Node {
      Integer body;
      Node nextNode;

      Node(Integer value) {
         body = value;
      }
   }

   private void addNodeToEnd(Integer value) {
      if (start == null) {
         start = new Node(value);
         head = start;
         head.nextNode = null;
         return;
      }

      while (head.nextNode != null) {
         head = head.nextNode;
      }

      head.nextNode = new Node(value);
   }

   private void traverse() {
      head = start;
      while (head != null) {
         System.out.println(head.body);
         head = head.nextNode;
      }
   }

   public static void main(String[] args) {
      LinkedList ll = new LinkedList();

      ll.addNodeToEnd(5);
      ll.addNodeToEnd(10);
      ll.addNodeToEnd(15);

      ll.traverse();

   }
}

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Q1050. If you need to consume messages from the queue faster, which approach will you recommend - batching or concurrency ?

Design

Ans. Each has it's own advantages

Batching requires less resources but may result in loosing whole batch in case of failure whereas concurrency even though is little more expensive in terms of resources but would result in minimal loss in case of failure.

In case messages are to be consumed in a particular order, batching them in that order and then consuming them makes better sense.

if incoming messages are not continuous , it makes more sense to do concurrency as we need not wait for all messages to form a batch and flush. Though time sensitivity can be added but that would add unnecessary complexity.

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_{Like Discuss Correct / Improve concurrency vs batching concurrency multithreading batch}

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