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Sanjivani Rural Education Society’s
SANJIVANI K.B.P.POLYTECHNIC,
KOPARGAON
CLASS-TEST-I
Model Answer
Sub:- Java Programming
YEAR:- 2016-17
Sub. Code:- 17515
Class :- TYCM Div:- A
Dept. :- Computer Technology
Name of subject teacher:-Prof. Jadhav S.B.
Q1. Attempt any THREE
(3*3=9)
1. List all the java operators.
Answer : ( ½ mark each category)
.
Categories of operators are as follows:
i. Arithmetic operators
ii. Logical operators
iii. Relational operators
iv. Assignment operators
v. Conditional operators
vi. Increment and decrement operators
vii. Bit wise operators
2. What is Byte code? Explain Java Virtual Machine.
Answer: ( Bytecode 1 mark, 2 mark)
Byte Code:
As we know that all programming language compilers convert the source code to machine
code. Same job done by Java Compiler to run a Java program, but the difference is that Java
compiler convert the source code into intermediate code is called as bytecode.
JVM: This machine is called the Java Virtual machine and it exits only inside the computer
memory.
Following figure shows the process of compilation.
Java
Program
Java
Compiler
Source Code
Virtual
Machine
Byte Code
The Virtual machine code is not machine specific. The machine specific code is generated.
By Java interpreter by acting as an intermediary between the virtual machine and real
machines shown below
Byte Code
Virtual machine
Java
Interpreter
Machine code
Real Machine
3. What this (?: ) operator is called? Explain with suitable example.
Answer : (Correct explanation with example 3 marks)
The character pair ?: is a ternary operator of Java, which is used to construct
conditional expressions of the following form:
Expression1 ? Expression2 : Expression3
The operator ? : works as follows:
Expression1 is evaluated if it is true then Expression2 is evaluated and becomes the value of
the conditional expression. If Expression1 is false then Expression3 is evaluated and its value
becomes the conditional expression.
For example:
A=3;
B=4;
C=(A<B)?A:B;
C=(3<4)?3:4;
C=3
3. State four decision making statements along with their suitable syntax.
Answer :
1. if statement
1. Simple if
if (condition)
{
Statement 1;
Statement 2;
}
2. if..else
if (condition)
{
Statement 1;
Statement 2;
}
else
{
Statement 3;
Statement 4;
}
nested if- else
if (condition1)
{
if (condition2)
{
Statement block1;
}
else
{
Statement block2;
}
}
else
{
Statement block3;
}
Statement 4;
2. switch statement
Syntax: switch(condition)//
condition means case value
{
case value-1:statement
block1;break; case value2:statement block2;break;
case value-3:statement
block3;break;
…
default: statement
block-default;break;
}
statement a;
Q2. Attempt any TWO
(4*2=8)
1. Write all primitive data types available in java along with their storage sizes in bytes.
Answer : (primitive types ½ mark each)
In a primitive data types, there are two categories


Numeric means Integer, Floating points
Non-numeric means Character and Boolean
Following table shows the datatypes with their size and ranges.
Data type
byte
boolean
char
short
Int
long
float
double
Size (byte)
Range
1
-128 to 127
1
True or false
2
A-Z,a-z,0-9,etc.
2
-32768 to 32767
4
(about) -2 million to 2 million
8
(about) -10E18 to 10E18
4
-3.4E38 to 3.4E18
8
-1.7E308 to 1.7E308
Fig: Datatypes with size and range
2. State all features of Java. Explain any two.
Answer : (List of features 1 mark, description 1 mark each)
Features of Java are as follows:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Compiled and Interpreted
Platform Independent and portable
Object- oriented
Robust and secure
Distributed
Familiar, simple and small
Multithreaded and Interactive
High performance
Dynamic and Extensible
1. Compiled and Interpreted
Basically a computer language is either compiled or interpreted. Java comes together both
these approach thus making Java a two-stage system.
Java compiler translates Java code to Bytecode instructions and Java Interpreter generate
machine code that can be directly executed by machine that is running the Java program.
2. Platform Independent and portable
Java supports the feature portability. Java programs can be easily moved from one
computer system to another and anywhere. Changes and upgrades in operating systems,
processors and system resources will not force any alteration in Java programs. This is reason
why Java has become a trendy language for programming on Internet which interconnects
different kind of systems worldwide. Java certifies portability in two ways.
First way is, Java compiler generates the bytecode and that can be executed on any
machine. Second way is, size of primitive data types are machine independent.
3. What are the uses of super and this keyword with respect to inheritance?
Answer : ( use of super 2 marks, this 2 marks)
Use of Super Keyword
A subclass constructor used to construct the instance variable of both the subclasses and
superclass. The subclass constructor uses the keyword super to invoke the constructor method of
the superclass. To use the super keyword following rules must be followed:
 super is always used within the subclass method constructor method.
 The call to superclass constructor must appear first statement within the subclass
constructor.
 The parameter used with super call must match the order and type of the instance
variable declared in the super class.
Use of this keyword
When the instance method or constructor being called by an object, then the object is
called ‘object under execution’ which is always pointed by ‘this’ pointer.

The members of the current object such as constructor or instance variables can be
referred by using this operator.
1. this() can be used to invoke current class constructor.
2. this keyword can be used to invoke current class method (implicitly)
3. this can be passed as an argument in the method call.
4. this can be passed as argument in the constructor call.
5. this keyword can also be used to return the current class instance.
Q3. Attempt any TWO
(4*2=8)
1. Describe different forms of inheritance.
Answer : (any four 1 mark each)
Different types of inheritance are available:
1. Single Inheritance (Only one super class)
2. Hierarchical Inheritance (One super class many subclasses)
3. Multilevel Inheritance (Derived from a derived class)
4. Hybrid Inheritance (Combination of above three types)
Single inheritance When a class extends another one class only then we call it a single inheritance. The below flow
diagram shows that class B extends only one class which is A.
Here A is a parent class of B and B would be a child class of A.
“Multiple Inheritance” refers to the concept of one class extending (Or inherits) more than one
base class. The problem with “multiple inheritance” is that the derived class will have to manage
the dependency on two base classes.
Multilevel inheritance refers to a mechanism in OO technology where one can inherit from a
derived class, thereby making this derived class the base class for the new class. As you can see in
below flow diagram C is subclass or child class of B and B is a child class of A.
2. What is constructor? Explain constructor overloading with example.
Answer : (Constructor description 2 marks, Example program 2 marks)
Constructor
 Objects once created must be given some initial values, this can be done using two methods
as stated above one is using dot operator and another is using parameterized method. But
it is tedious task to initialize all variables (i.e. object) like this.
 It is easy and simple to initialize an object when it is created. Java supports a special type
of method called constructor.
 A constructor initializes an object immediately upon creation. It has the same name as the
class in which it is defined and is syntactically similar to a method.
 Once defined, the constructor is automatically called immediately after the object is created
and before the new operator completes.
 Constructors have no return type, not even void. This is because the implicit return type of
a class’s constructor is the class type itself.
3. Define a class having one 3 digit number, num as data member, initialize and display
reverse of that number.
(Logic 2-M, Syntax 2-M)
class reverse
{
public static void main(String args[])
{
int num = 253;
int q,r;
for (int I = 0; i<3; i++)
{
q = num / 10; r = num % 10;
System.out.println(r);
Num = q;
}
}
}
public class PrimeNumCheck {
public boolean isPrimeNumber(int number){
for(int i=2; i<=number/2; i++){
if(number % i == 0){
return false;
}
}
return true;
}
public static void main(String a[]){
PrimeNumCheck mpc = new PrimeNumCheck();
System.out.println("Is 17 prime number? "+mpc.isPrimeNumber(17));
}
}
**** Best Of Luck ****