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

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Frequently asked at HCL Technologies ( Based on 3 feedback )

Q31. Difference between Checked and Unchecked exceptions ?

Core Java

Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked.

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.

Q32. What is a Final Variable ?

Core Java

Ans. Final variable is a variable constant that cannot be changed after initialization.

Sample Code for final variable

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Very Frequently asked. Usually asked along with String Class related questions.

Q33. What is an immutable class ?

Core Java

Ans. Class using which only immutable (objects that cannot be changed after initialization) objects can be created.

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Very frequently asked in phone and walk in interviews.

Q34. What are Marker Interfaces ? Name few Java marker interfaces ?

Core Java

Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote

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Very frequently asked. Usually difference between String,StringBuffer and StringBuilder is asked in different variations.

Q35. Difference between StringBuffer and StringBuilder ?

Core Java

Ans. StringBuffer is synchronized whereas StringBuilder is not.

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Q36. What is reflection ?

Ans. It is the process of examining / modifying the behaviour of an object at runtime.

Sample Code for reflection

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Q37. What is Generalization and Specialization in terms of casting ?

Core Java

Ans. Generalization or UpCasting is a phenomenon where a sub class is prompted to a super class, and hence becomes more general. Generalization needs widening or up-casting. Specialization or DownCasting is a phenomenon where a super class is narrowed down to a sub class. Specialization needs narrowing or down-casting.

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Very Frequently asked.

Q38. Explain throw, throws , try and catch in Java ?

Core Java

Ans. throw is used to re throw an exception.throws is used to declare that the method throws the respective exceptions.try block is used to identify if the respective block has thrown any exception.catch is used to catch the exception that has been thrown by the respective try block.

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Usually asked to entry level software developers.

Q39. Write a program to swap two variables without using third

Core Java

Ans. public static void main(String[] args) {
   int num1 = 1;
   int num2 = 2;
   num1 = num1^num2;
   num2 = num1^num2;
   num1 = num1^num2;
   System.out.print("num1 = " + num1 +", num2 = "+num2);
}

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Q40. If an Abstract class has only abstract methods, What's the difference between such a class and an interface ?

Core Java

Ans. Such a class still can have member elements which can be inherited and hence facilitate code reuse. Moreover Abstract class can have non final static elements whereas interfaces are only allowed to have static final elements.

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Q41. What are the problems one could face while working with serverless technologies like AWS Lambda ?

Amazon Web Services (AWS)

Ans. Warm up time for certain technologies like Java ( JVM Warmup )

Performance

Size of Deployable ( Bigger size packaging should go in S3 )

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Very Frequently asked.Favorite question in Walk in drive for many Indian service companies.

Q42. What is a Final Class ?

Ans. A Class that cannot be sub classed.

Sample Code for final class

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Q43. What is a Static import ?

Core Java

Ans. By static import , we can access the static members of a class directly without prefixing it with the class name.

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Q44. Advantage of Collection classes over Arrays ?

Core Java

Ans. Collections are re-sizable in nature. We can increase or decrease the size as per recruitment.
Collections can hold both homogeneous and heterogeneous data's.
Every collection follows some standard data structures.
Collection provides many useful built in methods for traversing,sorting and search.

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Very frequently asked Hibernate interview question. Frequently asked in TCS ( based on 2 feedback )

Q45. What are different types of associations in Hibernate ?

Hibernate

Ans. There are 4 types of associations in Hibernate

One to One
One to Many
Many to One
Many to Many

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Very frequently asked if being interviewed for hibernate. Frequently asked in Tata Consultancy (TCS) and Overstock.com

Q46. Difference between load and get ?

Hibernate

Ans. If id doesnt exist in the DB load throws an exception whereas get returns null in that case.get makes the call to DB immediately whereas load makes the call to proxy.

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Q47. What are some different logging levels for log4j ?

Log4j

Ans. DEBUG
ERROR
ALL
WARN
INFO
FATAL
OFF
TRACE
TRACE_INT
WARN

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Q48. How are values passed in Java ? By value or reference ?

Core Java

Ans. Java only provides pass by value.

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Q49. What was the driving force to introduce default methods in Interfaces wef from Java 8 ?

Core Java

Ans. Earlier any class implementing an interface was supposed to implement all methods declared in an interface. There was no place for optionally implementing all or subset of methods.Though we have abstract classes wherein we could have provided such a mechanism by declaring some methods as abstract while providing definition for some. But as Abstract classes have a body and are comparatively heavier than interfaces and interfaces associate closely to the concept of providing interfacing than abstract classes, Java might have though of providing optional implementation for default methods. This way same interface can be reused in variety of ways rather than making copies of an interface to suit different needs.

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Very Frequently asked to Senior Software Engineers or Developers.

Q50. Describe some of the Design Patterns you have used ?

Design

Ans. [Open Ended Answer]

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Q51. What is the difference between authentication and authorization ?

Authentication

Ans. Authentication is the process of verifying the identity and credentials of the user to authenticate him into the system.

whereas

Authorization is the process by which access to a segment , method or resource is determined.

Authorization is usually a step next to authentication.

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Q52. 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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Q53. What is a cookie ?

Java EE

Ans. A cookie is a small piece of text stored on a user's computer by the browser for a specific domain. Commonly used for authentication, storing site preferences, and server session identification.

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Frequently asked.

Q54. What is an Iterator?

Core Java

Ans. Iterator is an interface that provides methods to iterate over any Collection.

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Q55. What are transient variables in java?

Core Java

Ans. Transient variables are variable that cannot be serialized.

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Q56. What is a cloneable interface and what all methods does it contain?

Core Java

Ans. Cloneable is a declaration that the class implementing it allows cloning or bitwise copy of it's object state. It is not having any method because it is a MARKER interface.

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Q57. What is the use of HashCode in objects ?

Core Java

Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc.

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Very Frequently asked. Favorite question in walkins and telephonic interviews. Usually among first few questions. Asked in different variants. Must know for intermediate and expert professionals.Among Top 10 frequently asked questions.

Q58. What is rule regarding overriding equals and hashCode method ?

Core Java

Ans. A Class must override the hashCode method if its overriding the equals method.

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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)

Q59. Explain Singleton Design Pattern ?

Design

Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Q60. Can we have foreign key reference to a non primary key column ?

Database

Ans. Yes, but the respective key in the foreign table should be declared Unique.

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