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ISC Computer Science Viva Questions and Answers What is OOP? A: Object-oriented programming (OOP) is a programming paradigm that represents concepts as “objects” “objects” that have data felds (attributes that describe the object) and associated procedures knon as methods! Is Java an Object Oriented lanuae? A: "es! What is !ncapsulation? "ow is it implemented in Java? A: #inding up o$ data and associated $unctions together into a single unit called (class) is called %ncapsulation! %ncapsulation! &n 'ava it is implemented b the use o$ a class! What is #ata Abstraction? "ow is it implemented implemented in Java? A: Act o$ representing onl essential $eatures ithout including its background details is called Abstraction! *ata Abstraction can also be defned as the process o$ hiding the implementation details and shoing onl the $unctionalit! &n 'ava it is implemented b the use o$ inter$aces or b making the class abstract! What is Pol$morphism? "ow is it implemented in Java? A: &t literall means the abilit to take +more than one $orms,! he abilit o$ a method to behave in more than one $orm is called polmorphism! &n 'ava it is implemented b method ($unction) overloading (compile time polmorphism) and method overriding (runtime polmorphism)! polmorphism)! What is Inheritance? "ow is it implemented implemented in Java? A: he abilit o$ a class to adopt.share the properties (data and $unctions) completel or partiall $rom another class is called &nheritance! &n 'ava it is implemented b the use o$ the keord e/tends! What is the bene%t o& Inheritance? A: &t is a ver use$ul $eature as it provides the concept o$ reusabilit! Also it allos us to include or remove an $eatures to an e/isting class ithout modi$ing it! What is sini%cance o& import java'io'( in $our proram? A: he line imports all the classes o$ the java!io package into the current program! )ive some e*amples o& pac+aes' A: java!util java!lang etc! Wh$ did $ou write java'util pac+ae? ,onl$ i& $ou use classes li+e Scanner or Strin-o+eni.er/ Strin-o+eni.er/ A: o include the $unctions o$ the 0canner or 0tringokeni1er class $rom the java!util package! What is a class? A: A class is a blueprint or prototpe $rom hich objects are created!
What is an object? A: An object is an instance o$ a class! "ow to create an object? A: Objects o$ a class can be created as b declaring it and then instantiating it using the +ne, operator as $ollos: class-name object-name 2 ne class-name()3 %/ample: Point ob 2 ne Point()3 he above line creates an object o$ the Point class! Wh$ do $ou write 0u1ered2eader br 3 new 44' ? A: o activate the #u4er memor $or e5cient input and output operations! +br, is an object o$ the #u4ered6eader class! What is a 0u1er and what is its use? A: #u4er is a temporar memor used $or e5cient input and output operations! What is the &unction o& read5ine,/ method? A: read7ine() method reads a line o$ te/t (hich ou input) and returns the result in the $orm o$ a 0tring! Wh$ do we have main,/ &unction? A: he e/ecution o$ the program begins $rom the main() method! Wh$ is the main method public? A: 0o that it be accessible to the '89 hich begins to e/ecute the program $rom outside o$ the class! Wh$ is the main method static? A: 0o that it be available $or e/ecution ithout the need o$ an object! Is it compulsor$ to write Strin ars67 when runnin a proram in 0lueJ? A: o it is not compulsor hen e are running it in #lue'! #ut normall (in all other cases) it is alas better to have it as the '89 looks $or the main method ith a 0tring arra as a parameter! What is the use o& out in S$stem'out'println,/? A: +out, is an object o$ the +Print0tream class and a static data member o$ the,0stem, class hich is calling the println() $unction! What is the di1erence between print,/ and println,/ methods? A: he print() $unctions prints a line and the control remains on the same line hereas the println() $unction prints a line and the control moves on to the ne/t line! Can a pac+ae be called as a class? A: "es Package is actuall a class present in java!lang package! Wh$ do $ou write 8throws IO!9ception:?
A: ;or handling an input.output e/ceptions!
What are e*ceptions? A: %/ceptions are runtime errors hich prevent the program $rom orking normall! ;ention the two t$pes o& e*ceptions? A: nchecked %/ceptions = %/ceptions hich are not checked during compile time! %/ample: Arra&nde/OutO$#ound!
;ention other wa$s in which java handles e*ceptions' A: 'ava can handle e/ception using the tr-catch block thros keord and thro keord! What is the di1erence between throws and throw? A: >sing thros keord e can give sstem defned error message i$ an error occurs hile using thro keord e can $orce an e/ception and give user-defned error messages! What is tr$
Wh$ is the 8S: o& S$stem'out'println,/ &unction capital?
A: 0stem is the name o$ a class present in javalang package and hence it begins ith a capital letter as is the convention $or class names!
Wh$ is the 8S: o& Strin capital? A: 0ince 0tring is a class!
What is a variable? A: A variable is a named memor location hose value can change!
What is a constant? A: A constant is a literal hich cannot be changed!
"ow do $ou ma+e a variable into a constant? A: # adding the keord +fnal, be$ore a variable declarations! %/ample: fnal int a 2 B3
What are post%* and pre%* operators? A: #oth postf/ and pref/ operators change (increase or decrease) the value o$ a variable b C! &n postf/ the old value o$ the variable is frst used and then the variable is updated to the ne value hereas in pref/ the value o$ the variable is frst updated to the ne value and then this ne value is used!
What is the use o& %nal +e$word? A: ;inal can be used in three scenarios: a) fnal be$ore a variable makes it a constant! b) fnal be$ore a $unction declaration prevents it $rom being overridden! c) fnal be$ore a class declaration prevents it $rom being inherited!
What is a class variable? A: &nstance variables having the keord +static, be$ore it is a class variable! ;or ever object there is just one cop o$ the variable made!
What does S$stem'in'read,/ return? A: &t returns the number o$ btes read $rom the &nput 0tream as an integer!
Wh$ do $ou write 8Inteer'parseInt,br'read5ine,//:? A: he inputs in a java program comes in the $orm o$ 0tring objects hich are read using the br!read7ine() $unction! o i$ e ant the input in integer $orm e have to convert it into integer using the parse&nt() $unction o$ the &nteger rapper class!
What are wrapper class?
A rapper class is a class hich raps (encloses) around a data tpe and gives it an object appearance! Dherever the data tpe is reEuired as an object this object can be used!
What is t$pe conversion? =ame its t$pes' A:
What is the di1erence between castin and coercion? A: pe
What is the di1erence between i& and switch? A: (a) i$ can compare conditions $or all data tpes hereas sitch can onl check integers and characters! (b) all kinds o$ relations can be checked using i$ hereas onl eEualit relation can be checked using sitch!
What is &all
What is the di1erence between &or and while? A: he di4erence lies in the a the are commonl used! $or loop is commonl used hen the number o$ iterations are knon hereas hile loop is commonl used hen the number o$ iterations are not knon!
What is the di1erence between do
What is recursion?
A: &t is a process in hich a $unction calls itsel$ repeatedl until some base condition is satisfed!
What is the di1erence between recursion and iteration? A: 6ecursion is usuall sloer than iteration due to overhead o$ maintaining stack hereas &teration does not use stack so it,s $aster than recursion! 6ecursion uses more memor than iteration hereas &teration consume less memor! 6ecursion makes code smaller hereas &teration makes code longer!
What is the use o& return +e$word? A: return keord is used to return an value $rom a $unction! &t denotes the end o$ a $unction!
Can there be multiple return statements in a &unction? A: "es but onl one o$ them is e/ecuted!
Can two &unctions have the same name? )ive e*amples' A: "es! &n $unction overloading and $unction overriding!
What is the di1erence between &unction overloadin and &unction overridin? A: &n $unction overloading onl the $unction name is same but $unction signature (list o$ parameters) is di4erent hereas in $unction overriding both the $unction name as ell as $unction signature are same ;unction overloading takes place ithin the same class hereas $unction overriding takes place in a child and a parent class! ;unction overloading is an e/ample o$ static polmorphism hereas $unction overriding is an e/ample o$ dnamic polmorphism!
What is a constructor? A: &t is a member $unction ith the same name as that o$ a class and is automaticall called $or initiali1ing the variables o$ an object!
What is a cop$ constructor? A: &t is a constructor hich takes object as parameter and copies the value o$ the instance variable o$ that object to another object (creates a cop o$ an object)!
What is the de&ault access speci%er?
A: $riendl
What is a modi%er? A: A modifer is a keord placed in a class method or variable declaration that changes ho it operates! %/amples o$ modifers are: abstract fnal static etc!
What is the de&ault java pac+ae? A: java!lang
What is the use o& 8new: +e$word? A: &t is used $or dnamic memor allocation to re$erence data tpes!
What is the use o& 8this: +e$word? A: &t is used to re$er to the current object (the object hich calls the $unction)!
What are arra$s? A: Arras are a collection o$ variables o$ the same data-tpe re$erenced b a common name!
What is the sini%cance o& arra$s? A: &t helps to group similar variables under a common name hence reducing the number o$ names o$ variables e have to remember!
What is Strin-o+eni.er or Scanner and e*amples o& similar classes ,i& $ou used it/ A: 0tringokeni1er or 0canner is a class hich splits up an given string into tokens separated b delimiters!
=ame some other concepts related to Scanner>Strin-o+eni.er A: 0canner class 0tringokeni1er class split() $unction!
What is split,/ &unction?
A: split() $unction is a $unction o$ the 0tring class and it breaks up an 0tring into tokens and outputs the result in the $orm o$ an arra!
What is the use o& charAt,/ &unction? A: his $unction is used to e/tract characters at an given inde/ $rom a 0tring!
What is the di1erence between lenth,/ and lenth? A: length() $unction is used to fnd the number o$ characters present in a 0tring hereas length keord is used to fnd the number i$ cells in an arra!
What is the di1erence between brea+ and continue? A: break keord stops the complete loop and takes the control out o$ the loop hereas the continue keord just stops the current iteration and takes the control to the ne/t iteration!
What is the di1erence between selection sort and bubble sort? A: &n selection sort successive rounds are e/ecuted to select the element hich is reEuired to be placed in their sorted position hereas in bubble sort ever consecutive pairs o$ elements are compared and interchanged as reEuired to place them in their sorted position! &$ e are arranging an arra is ascending order then in selection sort e get the smallest element at ever pass hereas in bubble sort e get the largest element in ever pass!
What is the drawbac+ o& an arra$? A: &ts si1e cannot be changed!
When does 0inar$ search &ail? A: Dhen the arra is not sorted!
What is the di1erence between linear and binar$ search? A: 7inear search does not reEuire the arra to be sorted hereas binar search reEuires that the arra be sorted! 7inear search checks $or the search item in a linear $ashion $rom the beginning cell till the end hereas #inar search repeatedl dividing the arra into halves and the search takes place in one o$ the halves! he element is searched in the middle cell o$ ever hal$! he %/aminer ma ask ou to e/plain in brie$ the logic used ou to solve the program!
"ou kno hat ou have ritten so just give a brie$ summar o$ the logic used b ou! he %/aminer ma ask ou to tell hat is control variable in our loop! 0o i$ our loop is $or(int i 2 C3 i F2 B3 iGG) then the control variable is +i,! he %/aminer ma ask ou to tell hat is the return tpe o$ a $unction ou used! 0o i$ our $unction is boolean isPrime(int n) then the return tpe is +boolean,!
What is a ueue? )ive a real li&e e*ample' A: &t is a linear data structure hich $ollos the ;&;O (;irst &n ;irst out) pattern! 6eal li$e e/ample: Hueue at the ticket counter
What is a stac+? State it:s application' A: &t is a linear data structure hich $ollos the 7&;O (7ast &n ;irst out) pattern! 0tack memor is used in recursion! Application: &t can be used $or reversing strings $or evaluating postf/ e/pressions!
What is an abstract class? A: An abstract class is a class that is declared abstractIit ma or ma not include abstract methods! Abstract classes cannot be instantiated but the can be subclassed!
What is an abstract method? A: An abstract method is a method that is declared ithout an implementation (ithout braces and $olloed b a semicolon) like this: abstract void point(double / double )3
What is the di1erence between +e$words and reserved words? A: Jeords have a special meaning in a language and are part o$ the snta/! 6eserved ords are ords that cannot be used as identifers (variables $unctions etc!) because the are reserved b the language! %/ample: &n 'ava goto is a reserved ord but not a keord (as a conseEuence ou cannot use it at all)
What is the similarit$ between a method and a constructor? A: #elo are some o$ the similarities: C) #oth o$ them are member methods o$ an class! K) #oth can be parameterised or non-parameterised! L) #oth can be overloaded!
What is the di1erence between namin conventions and namin rules? A: 8iolating naming rules ill result in a snta/ error hereas violating naming conventions ill not result in an error!
What error will be enerated i& a space is iven between the loical A=# operator ,@@/? Will it be a compile
What is an inter&ace? "ow is it use&ul? A: &nter$ace is like a class that contains declaration o$ methods and variables ithout the $unction defnition! &t helps in implementing multiple inheritance!
What is super +e$word? A: &t is a keord hich is used to access the data members and methods o$ the super class $rom ithin the sub class!
What is super constructor? A: &t is a constructor hich is used to call the constructor o$ the super class and hence initiali1e the data members o$ the super class $rom ithin the sub class!
What is comple*it$? A:
What are the di1erent t$pes o& comple*ities? A: ime
What is the di1erence between Call b$ value and Call b$ re&erence? A:
