Ø What is
significance of import java.io.* in your program?
o A: The line
imports all the classes of the java.io package into the current program.
Ø Give some
examples of packages.
o A:
java.util, java.lang etc.
Ø Why did you
write java.util package? (only if you use classes like Scanner or
StringTokenizer)
o A: To
include the functions of the Scanner or StringTokenizer class from the java.util
package.
Ø What is a
class?
o A: A class
is the blueprint from which individual objects are created.
Ø What is an
object?
o A: An object
is an instance of a class.
Ø Why do you
write BufferedReader br = new ……. ?
o A: To
activate the Buffer memory for efficient input and output operations. ‘br’ is
an object of the BufferedReader class.
Ø Why do we
have main() function?
o A: The
execution of the program begins from the main() method.
Ø Why is the
main method public?
o A: So that
it be accessible to the JVM which begins to execute the program from outside of
the class.
Ø Why is the
main method static?
o A: So that
it be available for execution without the need of any object.
Ø Is it
compulsory to write String args[]?
o A: No it is
not.
Ø Why do you
write ‘throws IOEXception’?
o A: For
handling any input/output exceptions.
Ø What are
exceptions?
o A:
Exceptions are runtime errors which prevent the program from working normally.
Ø Mention the
two types of exceptions?
o A: Checked
Exceptions – Exceptions which are checked (handled) during compile time.
o Example:
IOException.
o Unchecked
Exceptions – Exceptions which are not checked during compile time.
o Example:
ArrayIndexOutOfBound.
Ø Mention
other ways in which java handles exceptions.
o A: Java can
handle exception using the try-catch block, throws keyword and throw keyword.
Ø What is the
difference between throws and throw?
o A: Using
throws keyword, we can give system defined error message if any error occurs,
while using throw keyword, we can force an exception and give user-defined
error messages.
Ø Name the
primitive data-types in java.
o A: byte,
short, int, long, float, double, char and boolean
Ø What are
comments? Name the different types.
o A: Comments
are statements which enhances the readability and understanding of the program.
They are not part of the program.
o The
different types are: single line (//….), multiple line (/* … */) and
documenting comment (/**….*/).
Ø Why is the
‘S’ of System.out.println() function capital?
o A: System is
the name of a class present in java,lang package and hence it begins with a
capital letter.
Ø Why is the
‘S’ of String capital?
o A: Since
String is a class.
Ø What is a
variable?
o A: A
variable is a named memory location whose value can change.
Ø What is a
constant?
o A: A
constant is a literal which cannot be changed.
Ø How do you
make a variable into a constant?
o A: By adding
the keyword ‘final’ before a variable declarations. Example: final int a = 5;
Ø What is the
use of final keyword?
o A: Final can
be used in three scenarios:
1.
final before a variable makes it a constant.
2.
final before a function declaration prevents it
from being overridden.
convention for class names.
3.
final before a class declaration prevents it from
being inherited.
Ø What is a
class variable?
o A: Instance variables
having the keyword ‘static’ before it is a class variable. For every object
there is just one copy of the variable made.
Ø Why do you
write ‘Integer.parseInt(br.readLine())’?
o A: The
inputs in a java program comes in the form of String objects which are read
using the br.readLine() function. Now if we want the input in integer form, we
have to convert it into integer using the parseInt() function of the Integer
wrapper class.
Ø What are
wrapper class?
o A wrapper
class is a class which wraps (encloses) around a data type and gives it an
object appearance. Wherever, the data type is required as an object, this
object can be used.
Ø What is type
conversion? Name its types.
o A:
Converting a calue of a particular data type into another data-type is called
type conversion. It is of two types:
1.
Implicit Type Conversion: When the conversion takes
place on its own without the programmer’s intervention.
2.
Explicit Type Conversion: When the conversion takes
place with the programmer’s intervention.
Ø What is the
difference between if and switch?
o A:
1.
if can compare conditions for all data types
whereas, switch can only check integers and characters.
2.
all kinds of relations can be checked using if
whereas only equality relation can be checked using switch.
Ø What is the
difference between for and while?
o A: The
difference lies in the way they are commonly used. for loop is commonly used
when the number of iterations are known whereas, while loop is commonly used
when the number of iterations are not known.
Ø What is the
difference between do-while and while?
o A: do-while
lop is exit controlled (i.e. condition is checked at the exit) and runs at
least once even if the condition is false whereas, while loop is entry
controlled (i.e. condition is checked at the entry) and does not run even once
if the condition is false.
Ø What is
recursion?
o A: It is a
process in which a function calls itself repeatedly until some base condition
is satisfied.
Ø What is the
difference between recursion and iteration?
o A: Recursion
is usually slower than iteration due to overhead of maintaining stack, whereas,
Iteration does not use stack so it’s faster than recursion.
Recursion
uses more memory than iteration, whereas, Iteration consume less memory.
Recursion
makes code smaller, whereas, Iteration makes code longer.
Ø What is the
use of return keyword?
o A: return
keyword is used to return any value from a function. It denotes the end of a
function.
Ø Can there be
multiple return statements in a function?
o A: Yes, but
only one of them is executed.
Ø Can two
functions have the same name? Give examples.
o A: Yes. In
function overloading and function overriding.
Ø What is the
difference between function overloading and function overriding?
o A: In
function overloading only the function name is same but function signature
(list of parameters) is different, whereas, in function overriding both the
function name as well as function signature are same
Function
overloading takes place within the same class, whereas, function overriding
takes place in a child and a parent class.
Function
overloading is an example of static polymorphism, whereas, function overriding
is an example of dynamic polymorphism.
Ø What is a
constructor?
o A: It is a
member function with the same name as that of a class and is automatically
called for initializing the variables of an object.
Ø What is the
default access specifier?
o A: friendly
Ø What is the
default java package?
o A: java.lang
Ø What is the
use of ‘new’ keyword?
o A: It is
used for dynamic memory allocation to reference data types.
Ø What is the
use of ‘this’ keyword?
o A: It is
used to refer to the current object (the object which calls the function).
Ø What are
arrays?
o A: Arrays
are a collection of variables of the same data-type referenced by a common
name.
Ø What is the significance
of arrays?
o A: It helps
to group similar variables under a common name, hence reducing the number of
names of variables we have to remember.
Ø What is
StringTokenizer or Scanner and examples of similar classes (if you used it)
o A:
StringTokenizer or Scanner is a class which splits up any given string into
tokens separated by delimiters.
Ø Name some
function of StringTokenizer class.
o A:
nextToken(), countToken(), hasMoreTokens() etc.
Ø Name some
function of Scanner class.
o A: next(),
nextInt(), hasNextInt() etc.
Ø Name some
other concepts related to Scanner/StringTokenizer
o A: Scanner
class, StringTokenizer class, split() function.
Ø What is
split() function?
o A: split()
function is a function of the String class and it breaks up any String into
tokens and outputs the result in the form of an array.
Ø What is the
use of charAt() function?
o A: This
function is used to extract characters at any given index from a String.
Ø What is the
difference between length() and length?
o A: length()
function is used to find the number of characters present in a String, whereas,
length keyword is used to find the number if cells in an array.
Ø What is the
difference between break and continue?
o A: break
keyword stops the complete loop and takes the control out of the loop, whereas,
the continue keyword just stops the current iteration and takes the control to
the next iteration.
Ø What is the
difference between selection sort and bubble sort?
o A: In
selection sort, successive rounds are executed to select the element which is
required to be placed in their sorted position, whereas, in bubble sort, every
consecutive pairs of elements are compared and interchanged as required to
place them in their sorted position.
If we are arranging an array is ascending
order, then in selection sort, we get the smallest element
at every pass, whereas, in bubble sort we
get the largest element in every pass.
Ø What is the
drawback of an array?
o A: Its size
cannot be changed.
Ø When does
Binary search fail?
o A: When the
array is not sorted.
Ø What is the
difference between linear and binary search?
o A: Linear
search does not require the array to be sorted, whereas, binary search requires
that the array be sorted.
Linear
search checks for the search item in a linear fashion from the beginning cell
till the end, whereas, Binary search repeatedly dividing the array into halves
and the search takes place in one of the halves. The element is searched in the
middle cell of every half.
The Examiner
may ask you to explain in brief the logic used you to solve the program.
You know
what you have written so just give a brief summary of the logic used by you.
The Examiner
may ask you to tell what is control variable in your loop.
So if your
loop is for(int i = 1; i <= 5; i++) then the control variable is ‘i’.
The Examiner
may ask you to tell what is the return type of a function you used.
So if your
function is Boolean isPrime(int n) then the return type is ‘boolean’.
Ø What is a
queue? Give a real life example.
o A: It is a
linear data structure which follows the FIFO (First In First out) pattern.
Real life
example: Queue at the ticket counter
Ø What is a
stack? State it’s application.
o A: It is a
linear data structure which follows the LIFO (Last In First out) pattern. Stack
memory is used in recursion.
Application:
It can be used for reversing strings.
All the best for your examinations
Regards
Sharma Tutorials Jamshedpur
