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Design - Interview Questions and Answers for 'Abs' - 29 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 292 Companies      basic        frequent

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Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews.
  Q2. Differences between abstract class and interface ?Core Java
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Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ).

A class can extend single abstract class whereas it can implement multiple interfaces.

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   Like         Discuss         Correct / Improve     java   classes   abstract class   interfaces     Asked in 80 Companies      basic        frequent


Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc )
  Q3. What is Dependency Injection or IOC ( Inversion of Control ) ?Design

Ans. It is a Design Pattern that facilitates loose coupling by sending the dependency information ( object references of dependent object ) while building the state of the object. Objects are designed in a manner where they receive instances of the objects from other pieces of code, instead of constructing them internally and hence provide better flexibility.

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   Like         Discuss         Correct / Improve     design patterns   ioc ( Inversion of Control )  dependency injection     Asked in 80 Companies      intermediate        frequent


  Q4. What is the use of Transient Keyword ?Core Java
Anonymous
Ans. It in Java is used to indicate that a field should not be serialized.

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   Like         Discuss         Correct / Improve     java   oops   serialization   transient   java keywords     Asked in 39 Companies      intermediate        frequent

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 Q5. Difference between Factory and Abstract Factory Design Pattern ?Design
Anonymous
Ans. Factory Pattern deals with creation of objects delegated to a separate factory class whereas Abstract Factory patterns works around a super-factory which creates other factories.

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Very frequently asked.Usually among first few questions.
  Q6. What is MVC ? Design
Anonymous
Ans. MVC is a Design Pattern that facilititates loose coupling by segregating responsibilities in a Web application

1. Controller receives the requests and handles overall control of the request
2. Model holds majority of the Business logic, and
3. View comprise of the view objects and GUI component

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 Q7. If you are given a choice to implement the code to either Insert a Record or Update if already exist, Which approach will you follow ?

1. Insert into the DB Table. If exception occurs, update the existing record.
2. Check if the record exists and update it if it exists, If not insert a new record.
Solution
admin
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Ans. In first case, there would be 2 DB calls in worst case and 1 in best case. In 2nd approach there will be always 2 DB calls.

Decision on the approach should depend on the following considerations -

1. How costly is the call to DB ? Are we using indices , hibernate etc

If calls to DB are costly , 1st approach should be the choice.

2. Exception Book keeping load upon exception.

The benefit of saving 1st call in approach 1 should be bigger than the Book keeping for the exception.

3. Probability of the exception in first apparoach.

If the DB Table is almost empty, it makes sense to follow Approach 1 as majority of the 1st calls will pass through without exception.

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   Like         Discuss         Correct / Improve     database   insert-update   db exceution plan   db strategy   design   architecture   technical lead


 Q8. Write a program to show thread usage in Java by implementing runnable interface2017-08-03 12:16:07

Ans. public class MyClass {
   static class MyThreadClass implements Runnable{

      public void start() {
         Thread t = new Thread(this,"threadName");
         t.start();
      }
      
      @Override
      public void run() {
         System.out.println("Hello");
         try {
            Thread.sleep(1000);
            System.out.println("Hello Again");
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
         
      }
      
   }
   
   public static void main(String[] args){
      MyThreadClass myThreadClass = new MyThreadClass();
      myThreadClass.start();
      
      MyThreadClass myThreadClass2 = new MyThreadClass();
      myThreadClass2.start();
   }
}

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 Q9. Difference between Factory and Strategy Design Pattern ?Design
Anonymous
Ans. Factory is a creational design pattern whereas Strategy is behavioral design pattern. Factory revolves around the creation of object at runtime whereas Strategy or Policy revolves around the decision at runtime.

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 Q10. What is a Cursor ?Database
Admin
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Ans. It's a facility that allows traversal over the records pulled from a table or combination of tables. Its like iterator in Java.

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   Like         Discuss         Correct / Improve     databases   sql   cursors   packages     Asked in 5 Companies      basic        frequent


Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
  Q11. Explain Singleton Design Pattern ?Design
Admin
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Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Frequently asked in face to face interviews.
  Q12. Write a program to print fibonacci series.Core Java

Ans. int count = 15;
int[] fibonacci = new int[count];
fibonacci[0] = 0;
fibonacci[1] = 1;
for(int x=2; x < count; x++){
fibonacci[x] = fibonacci[x-1] + fibonacci[x-2];
}

for(int x=0; x< count; x++){
System.out.print(fibonacci[x] + " ");
}

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 Q13. Does it make sense to clone an object which is supposed to be immutable ?Design2016-07-28 20:54:59

Ans. It make sense only if we intend to modify either of the object and would like to preserve original state in other. Otherwise we can reuse the original object by making it singleton.

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 Q14. Design an online shopping site system ?Design2016-12-13 11:06:10

Ans. AWS Services - CloudFront for distribution / caching, EC2 for computing, EBS for block storage , S3 for object storage , RDS for database , Kinesis for streaming , CloudWatch for monitoring.

Technologies - Java for back end with Spring Boot , Angular , RxJs for front end .

Architecture - Service Oriented. Multi layer.

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 Q15. What is a factory design pattern ?Design2017-01-09 13:21:43

Ans. Factory Design Patterns is the pattern that recommends creation of separate Factory Object for creation of other object.

So its like saying - If you want to create an object of ClassA, Talk to FactoryObject ( which is an object of FactoryClass ). FactoryObject in itself encapsulates the inputs and logic required to make the decision regarding the creation and construction of object.

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 Q16. Difference between Singleton and Factory Design Pattern ?Design2017-02-02 11:24:01

Ans. Both are creational design patterns but singleton facilitates in creation and reuse of single object whereas Factory deals with creation of multiple objects.

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 Q17. Design a Database Schema to store Employee Information with each employee having multiple addresses. Database2017-08-24 13:48:56

Ans. We can have 2 entities i.e EMPLOYEE and ADDRESS and can have a relationship Table , EMPLOYEE_ADDRESS having one to may relationship between the two.

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 Q18. What is abstraction ?Design2017-10-13 09:23:38

Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user.

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 Q19. What is the programming advantage of Immutability ?Design2018-03-31 08:33:05

 This question was recently asked at 'Overstock.com'.This question is still unanswered. Can you please provide an answer.


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 Q20. What are the disadvantages of immutability ?Design2018-03-31 08:33:36

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


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 Q21. What is immutability and What are it's disadvantages ?Design2018-06-20 12:20:19

 This question was recently asked at 'Bloomberg'.This question is still unanswered. Can you please provide an answer.


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 Q22. Design database schema for Facebook like application.Database2018-06-21 18:01:57

 This question was recently asked at 'Symantec'.This question is still unanswered. Can you please provide an answer.


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Library Management System has always been the favorite question. This questions is asked irrespective of level.
 Q23. Write data models and service end points for Library Management System ?Architecture2018-06-30 13:43:10

Ans. Following could be the business sub domains or database schemas in such a system

1. Users / Members
2. Sourcing
3. Inventory Management
4. Operations

Following services end points could be there

1. Users - addNewUser ( put ), removeUser ( post )
2. Sourcing - addSupplier ( put ), removeSupplier ( post )
3. Inventory Management - getInventory ( get )
4. Operations - checkIn ( post ), checkout ( post )

There could be following Tables in Database

1. Users / Members - MEMBER, MEMBERSHIP_TYPE
2. Sourcing - SUPPLIER, SUPPLIER_PRODUCT, PRODUCT_REORDER_LEVELS
3. Inventory Management - INVENTORY,PRODUCTS
4. Operations - TRANSACTION

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 Q24. How to avoid cloning, serialization in the singleton class ?Design2019-01-04 10:12:26

Ans. For Cloning-exception,For deserialization-read.resolve()

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 Q25. Create DB schema for Employee, Department.Database2019-04-06 12:42:21

 This question was recently asked at 'RiseSmart India,RiseSmart'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     db schema  database schema  database design     Asked in 2 Companies


 Q26. Find the second largest array element without sorting?Design2019-08-07 13:14:31

Ans. We initialize two variables first and second to INT_MIN as,
first = second = INT_MIN
then Start traversing the array,
If the current element in array say arr[i] is greater
than first. Then update first and second as,
second = first
first = arr[i]
If the current element is in between first and second,
then update second to store the value of current variable as
second = arr[i]
then Return the value stored in second.

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 Q27. How would you design the database schema for an event?Database2020-01-10 15:49:51

 This question was recently asked at 'CVS Healthcare'.This question is still unanswered. Can you please provide an answer.


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 Q28. Write a Program to swap 2 variables ( using 3rd variable )Core Java2017-07-25 19:41:20

Ans. int x = 1;
int y = 2;
int z = x;
x = y;
y = z;

System.out.println("x="+x);
System.out.println("y="+y);

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 Q29. Write a Program to swap two variables ( without using 3rd variable )2017-07-25 19:42:32

Ans.
int x = 1;
int y = 2;

x = x+y;
y = x-y;
x = x-y;

System.out.println("x="+x);
System.out.println("y="+y);

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 Q30. Which method needs to be implemented if a class is implementing comparable interface ?Core Java
a. comp
b. compare
c. compareTo
d. compareEquals

Ans.c. compareTo


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