DipIETE
– CS (OLD SCHEME)
Code: DC12 Subject: OOPS THRU JAVA
Time: 3 Hours
Max. Marks: 100
NOTE: There are 9 Questions in all.
· Question 1 is compulsory and
carries 20 marks. Answer to Q.1 must be written in the space provided for it in
the answer book supplied and nowhere else.
· Out of the remaining EIGHT
Questions answer any FIVE Questions. Each question carries 16 marks.
· Any required data not explicitly
given, may be suitably assumed and stated.
Q.1 Choose
the correct or best alternative in the following: (2 
10)
a.
Which
of the following is a valid octal number?
(A) 080 (B) 0A6
(C) 091 (D) 072
b.
Consider
the following class definition:
class A {
A(int x) { … }
A(int x, int y) { … }
Which of the following
statements cannot be used to construct objects of type A?
(A) A a = new A(10); (B) A a = new A();
(C) A a = new A(20, 30); (D) None of the above
c.
All
the objects of a class use the same copy of a(n) ___________ variable.
(A) final (B) protected
(C) static (D) public
d.
A
package in Java is a collection of
__________ .
(A) Output files (B) Class
files
(C) Text files (D) Source
files
e.
Which
of the following is true?
(A) Error and Exception are subclasses of Throwable class.
(B) Error and Throwable are subclasses of Exception class.
(C) Throwable and Exception are subclasses of Error class.
(D) None of the above.
f.
What
will be the output of the following program?
class demo{
public static void main(String
args[]) {
boolean a = true, b = false;
System.out.println("a
= " + a);
return;
System.out.println("b
= " + b);
}
}
(A) a = trueb= false
(B) a = true
(C) a = true b= false
(D) Program won’t compile giving
message "unreachable statement".
g.
Which
of the following is an illegal flow control statement?
(A) break; (B) break label;
(C)
continue; (D)
continue (label);
h.
To
achieve multiple inheritance in Java, __________ are used.
(A) interfaces (B) Constructors
(C) Arrays (D) Operators
i.
Which
of the following are passed by reference in Java?
(A)
Integers (B) Arrays
(C) Booleans (D) Characters
j.
Identify
the incorrect statement among the following statements.
(A) Java classes need not have a
main() method.
(B) Variables cannot be defined
within the for loop.
(C) Abstract classes cannot be
instantiated.
(D) There can be any number of catch clauses
after a try block.
Answer any FIVE Questions out
of EIGHT Questions.
Each
question carries 16 marks.
Q.2 a. Briefly explain the three uses of break keyword. (6)
b. Identify the error(s), if any, in the
following code segments. (4)
(i) int
x = 10, y = 20;
System.out.println("Output: " +
(x + y)++);
(ii) class box {
int length,
height, depth;
private box() { length = height = depth
= 0; }
int area() { return length * height *
depth;}
}
class
demo{
public static void main(String args[])
{
box b = new box();
System.out.println("Area
= " + b.area());
}
c. What are the various uses of super keyword? Explain with the help of
examples. (6)
Q.3 a. Briefly explain the two main features of Java that make it a
useful programming language for the Internet. (4)
b. What is a static block? What
is it used for? (3)
c. Differentiate
between the following:
(i) call by value and call by reference
(ii) throw and throws
(iii) do...while and while
loops (3
3)
Q.4 a. Distinguish between single inheritance and
multiple inheritance. Which feature(s) of Java helps to realize the benefits of
multiple inheritance? Explain with an example. (8)
b. When an overloaded method is invoked, how does Java decide? Which version of overloaded methods is to be called? What are the advantages of having different methods with the same name? (4)
c. What
is the purpose of garbage collection in Java? (4)
Q.5 a. How does a package help in organising classes? Explain with the
help of a suitable example. (4)
b. What is an applet? How is it
different from Java application program? (4)
c. Find out the value of a after each operation (assume for each operation initial value of a is 22 and b is 5).
(i) a
<< 3
(ii) a ^ b
(4)
d.
What
are the four categories of visibility Java addresses for class members? (4)
Q.6 a. What do you understand by recursion? What is the output of the
following code segment? Show the steps also.
(8)
class recur{
public static void main(String args[]){
int sum = meth(3, 5);
System.out.println("sum=
" + sum);
}
static int meth(int a, int b){
int result;
if (a == -b)
result 0;
else
result = a +
meth(a, (b - 1));
return result;
}
}
b. Design a class Complex having a real part (x) and an imaginary part (y). Provide methods to perform the following on complex numbers:
(i) Add two complex numbers.
(ii) Multiply two complex numbers.
(iii) Display a complex number in the form: x + i y. (8)
Q.7 a. Explain
the term polymorphism and different ways Java implements polymorphism. (8)
b. How is exception handling done in Java using the keywords try, throw and catch? (8)
Q.8 a. Define a class Person having name as a data member. Inherit two more classes Student and Employee from Person. To the class Student, add data members course, marks and year; and to the class Employee, add data members department and salary. Write display() method in all the three classes to display the relevant details of the corresponding class. Provide the necessary methods to show dynamic method dispatch concept. (10)
b. What is the significance of this keyword? Where is it used? Explain with the help of an example. (6)
Q.9 Write
short notes on the following:
(i)
Byte
streams and character streams
(ii)
Lifetime
of variables
(iii)
PrintWriter
class
(iv)
Extending
an interface (4
4)