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Design - Interview Questions and Answers for 'Abs' - 26 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 ) and Epam Systems
  Q1. Difference between == and .equals() ?Core Java
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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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
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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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 83 Companies      intermediate        frequent

Very frequently asked.Usually among first few questions.
  Q4. What is MVC ? Design
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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  Q5. What is the use of Transient Keyword ?Core Java
Ans. It in Java is used to indicate that a field should not be serialized.

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 Q6. Difference between Factory and Abstract Factory Design Pattern ?Design
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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 Q7. Difference between Factory and Strategy Design Pattern ?Design
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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 Q8. 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
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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 Q9. What is abstraction ?Design
Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user.

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 Q10. How to avoid cloning, serialization in the singleton class ?Design
Ans. For Cloning-exception,For deserialization-read.resolve()

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 Q11. What is a Cursor ?Database
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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Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
  Q12. Explain Singleton Design Pattern ?Design
Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Frequently asked in face to face interviews.
  Q13. 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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 Q14. Does it make sense to clone an object which is supposed to be immutable ?Design
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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   Like         Discuss         Correct / Improve     clone  clone objects  prototype design pattern   immutable  immutability  immutability  cloning

 Q15. Design an online shopping site system ?Design
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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 Q16. What is a factory design pattern ?Design
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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 Q17. Difference between Singleton and Factory Design Pattern ?Design
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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 Q18. Design a Database Schema to store Employee Information with each employee having multiple addresses. Database
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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 Q19. What is the programming advantage of Immutability ?Design
 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 ?Design
 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 ?Design
 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.Database
 This question was recently asked at 'Symantec'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     database design     Asked in 1 Companies      expert

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 ?Architecture
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. Create DB schema for Employee, Department.Database
 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

 Q25. Find the second largest array element without sorting?Design
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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 Q26. How would you design the database schema for an event?Database
Ans. Broad question, but if the company need velocity, think about use a NO SQL instead of regular SQL databases.

Also prefers materialized views instead of joins to fetch data quickly.

Regarding the database design, there are very good design tools for professional database (to develop proper indexes and good database design) one of the best is QuickDBD

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 Q27. 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
 Q28. What is Dirty Read in Database Transactions ?Database
a. Data Read by Transaction 2 which hasn't yet updated by Transaction 1
b. Data Read by Transaction 2 which has been updated and commited by Transaction 1
c. Data Read by Transaction 2 which has been updated but not commited by Transaction 1
d. Inability of Transaction 2 to read Data when Transaction 1 is updating.

Ans.c. Data Read by Transaction 2 which has been updated but not commited by Transaction 1
 Q29. Which of the following is not true for abstract classes ?Core Java
a. Abstract Class is only meant to be sub classed and not supposed to be instantiated.
b. Abstract class handlers can be used to handle derived class objects.
c. We can't have an abstract class without abstract methods.
d. Abstract class has member elements.

Ans.c. We can't have an abstract class without abstract methods.
 Q30. Which of the following class creates immutable objects ?Core Java
a. String
b. StringBuffer
c. StringBuilder
d. None of these create immutable objects.

Ans.a. String

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