Interview Questions and Answers for 'Tata Consultancy (TCS)' | Search Java Interview Question

Interview Questions and Answers for 'Tata Consultancy (TCS)' - 84 question(s) found - Order By Newest

Frequently asked to fresh graduates and less experienced developers. Among the first few questions in many interviews.

Q1. What are the difference between composition and inheritance in Java?

Core Java

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Ans. Composition - has-a relationship between objects.
Inheritance - is-a relationship between classes.

Composition - Composing object holds a reference to composed objects and hence relationship is loosely bound.
Inheritance - Derived object carries the base class definition in itself and hence its tightly bound.

Composition - Used in Dependency Injection
Inheritance - Used in Runtime Polymorphism

Composition - Single class objects can be composed within multiple classes.
Inheritance - Single class can only inherit 1 Class.

Composition - Its the relationship between objects.
Inheritance - Its the relationship between classes.

Sample Code for inheritance

Sample Code for composition

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Q2. Which are the different segments of memory ?

Core Java

^Anonymous

Ans. 1. Stack Segment - Contains primitives, Class / Interface names and references.

2. Heap Segment - Contains all created objects in runtime, objects only plus their object attributes (instance variables), Static variables are also stored in heap.

3. Code Segment - The segment where the actual compiled Java bytecodes resides when loaded

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Very frequently asked to Fresh graduates.

Q3. What is the difference between Encapsulation and Abstraction?

Core Java

^Anonymous

Ans. 1.Abstraction solves the problem at design level while encapsulation solves the problem at implementation level

2.Abstraction is used for hiding the unwanted data and giving relevant data. while Encapsulation means hiding the code and data into a single unit to protect the data from outside world.

3. Abstraction lets you focus on what the object does instead of how it does it while Encapsulation means hiding the internal details or mechanics of how an object does something.

4.For example: Outer Look of a Television, like it has a display screen and channel buttons to change channel it explains Abstraction but Inner Implementation detail of a Television how CRT and Display Screen are connect with each other using different circuits , it explains Encapsulation.

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture.

Q4. What is the difference between final, finally and finalize() ?

Core Java

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Ans. final - constant variable, objects cannot be de-referenced, restricting method overriding, restricting class sub classing.

finally - handles exception. The finally block is optional and provides a mechanism to clean up regardless of what happens within the try block. Use the finally block to close files or to release other system resources like database connections, statements etc.

finalize() - method helps in garbage collection. A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state.

Sample Code for final

Sample Code for finally

Sample Code for finalize

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Frequently asked question in companies using Hibernate.

Q5. What is Lazy Initialization in Hibernate ?

Hibernate

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Ans. It's a feature to lazily initialize dependencies , relationship and associations from the Database. Any related references marked as @OneToMany or @ManyToMany are loaded lazily i.e when they are accessed and not when the parent is loaded.

Sample Code for Lazy Initialization

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Q6. Explain OOPs

or

Explain OOPs Principles

or

Explain OOPs Concepts

or

Explain OOPs features

or

Tell me something about OOPs

Core Java

^{2017-06-13 08:25:45}

Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features

1. Inheritance for Code Reuse
2. Abstraction for modularity, maintenance and agility
3. Encapsulation for security and protection
4. Polymorphism for flexibility and interfacing

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Recently asked in TCS , Tech Mahindra, HCL , Accenture and Fidelity.

Q7. Explain Flow of Spring MVC ?

Spring

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Ans. The DispatcherServlet configured in web.xml file receives the request.

The DispatcherServlet finds the appropriate Controller with the help of HandlerMapping and then invokes associated Controller.

Then the Controller executes the logic business logic and then returns ModeAndView object to the DispatcherServlet.

The DispatcherServlet determines the view from the ModelAndView object.

Then the DispatcherServlet passes the model object to the View.

The View is rendered and the Dispatcher Servlet sends the output to the Servlet container.

Finally Servlet Container sends the result back to the user.

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Basic and Very Frequently asked.

Q8. What is Polymorphism in Java ?

Core Java

^{2016-11-06 09:10:54}

Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

Sample Code for overloading

Sample Code for overriding

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Q9. What is a String Pool ?

Core Java

^Anonymous

Ans. String pool (String intern pool) is a special storage area in Java heap. When a string is created and if the string already exists in the pool, the reference of the existing string will be returned, instead of creating a new object and returning its reference.

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Frequently asked question in companies using hibernate.

Q10. Difference between first level and second level cache in hibernate ?

Hibernate

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Ans. 1. First level cache is enabled by default whereas Second level cache needs to be enabled explicitly.

2. First level Cache came with Hibernate 1.0 whereas Second level cache came with Hibernate 3.0.

3. First level Cache is Session specific whereas Second level cache is shared by sessions that is why First level cache is considered local and second level cache is considered global.

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

Q11. Difference between TreeMap and HashMap ?

Core Java

^Anonymous

Ans. They are different the way their elements are stored in memory. TreeMap stores the Keys in order whereas HashMap stores the key value pairs randomly.

Sample Code for treemap

Sample Code for hashmap

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Very frequently asked across all types of companies.

Q12. Difference between HashMap and Hashtable?

Core Java

^Anonymous

Ans. Hashtable is synchronized whereas HashMap is not.HashMap allows null values whereas Hashtable doesnt allow null values.

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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.

Q13. 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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Very Frequently asked across all type of companies and across all levels.

Q14. Difference between Public, Private, Default and Protected ?

Core Java

^Anonymous

Ans. Private - Not accessible outside object scope.

Public - Accessible from anywhere.

Default - Accessible from anywhere within same package.

Protected - Accessible from object and the sub class objects.

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

Q15. What is a final method ?

Core Java

^Anonymous

Ans. Its a method which cannot be overridden. Compiler throws an error if we try to override a method which has been declared final in the parent class.

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Q16. What is casting?

Core Java

^Anonymous

Ans. There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference

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Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies.

Q17. Difference between Overloading and Overriding ?

Core Java

^Anonymous

Ans. Overloading - Similar Signature but different definition , like function overloading.

Overriding - Overriding the Definition of base class in the derived class.

Sample Code for overloading

Sample Code for overriding

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Q18. Difference between SAX and DOM Parser ?

Xml

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Ans. A DOM (Document Object Model) parser creates a tree structure in memory from an input document whereas A SAX (Simple API for XML) parser does not create any internal structure.

A SAX parser serves the client application always only with pieces of the document at any given time whereas A DOM parser always serves the client application with the entire document no matter how much is actually needed by the client.

A SAX parser, however, is much more space efficient in case of a big input document whereas DOM parser is rich in functionality.

Use a DOM Parser if you need to refer to different document areas before giving back the information. Use SAX is you just need unrelated nuclear information from different areas.

Xerces, Crimson are SAX Parsers whereas XercesDOM, SunDOM, OracleDOM are DOM parsers.

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Frequently asked to fresh graduates and less experienced.

Q19. Difference between Composition and Inheritance ?

Core Java

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Ans. Inheritance means a object inheriting reusable properties of the base class. Compositions means that an abject holds other objects.

In Inheritance there is only one object in memory ( derived object ) whereas in Composition , parent object holds references of all composed objects.

From Design perspective - Inheritance is "is a" relationship among objects whereas Composition is "has a" relationship among objects.

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Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc )

Q20. 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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Q21. What are the different types of inner classes ?

Core Java

^Anonymous

Ans. Simple Inner Class,
Local Inner Class,
Anonymous Inner Class,
Static Nested Inner Class.

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

Q22. What is a Final Variable ?

Core Java

^Anonymous

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 in phone and walk in interviews.

Q23. What are Marker Interfaces ? Name few Java marker interfaces ?

Core Java

^Anonymous

Ans. These are the interfaces which have no declared methods.Serializable and cloneable are marker interfaces.

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Frequently asked to fresh graduates.

Q24. What is a Deadlock ?

Operating System

^Anonymous

Ans. When two threads are waiting each other and cant precede the program is said to be deadlock.

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Very frequently asked.Usually among first few questions.

Q25. 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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Q26. What is Generalization and Specialization in terms of casting ?

Core Java

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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 in companies using SOA.

Q27. What are RESTful Web Services ?

Rest

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Ans. REST or Representational State Transfer is a flexible architecture style for creating web services that recommends the following guidelines -

1. http for client server communication,
2. XML / JSON as formatiing language ,
3. Simple URI as address for the services and,
4. stateless communication.

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Q28. What are the contents of Hibernate configuration file ( hibernate.cfg.xml ) ?

Hibernate

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Ans. HBM Files ( Mapping )
DB Connection ( DB Connection String , User Name , Password , Pool Size )
SQL Dialect ( SQL variant to be generated )
Show SQL ( Show / No show SQL on Console )
Auto Commit ( True / False )

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Frequently asked to fresh graduates.

Q29. What is ACID ?

Database

^{2016-11-04 08:09:44}

Ans. ACID stands for Atomicity, Consistency, Isolation, Durability is a set of properties of database transactions.

Atomicity means all or nothing. i.e parts of a transaction shouldn't commit if any one of them fails. Either the whole transaction should succeed or it should be complete rollback.

Consistency means that any transaction should lead database from one stabe state to another.

Isolation means that the execution of transaction results in a system state that would be obtained if transactions were executed serially.

Durability means that when a transaction is committed it forms the permanent state of database.

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Q30. If an Abstract class has only abstract methods, What's the difference between such a class and an interface ?

Core Java

^{2017-05-07 07:26:29}

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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Q31. 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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Very Frequently asked.Favorite question in Walk in drive for many Indian service companies.

Q32. What is a Final Class ?

^Anonymous

Ans. A Class that cannot be sub classed.

Sample Code for final class

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

Q33. What is an immutable class ?

Core Java

^Anonymous

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

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Q34. What is a Static import ?

Core Java

^Anonymous

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

Q35. Difference between StringBuffer and StringBuilder ?

Core Java

^Anonymous

Ans. StringBuffer is synchronized whereas StringBuilder is not.

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Q36. What is reflection ?

^Anonymous

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

Sample Code for reflection

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

Q37. Difference between load and get ?

Hibernate

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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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Q38. What are some different logging levels for log4j ?

Log4j

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

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Q39. What are the problems one could face while working with serverless technologies like AWS Lambda ?

Amazon Web Services (AWS)

^{2018-01-30 18:05:47}

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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Q40. What is a cookie ?

Java EE

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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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