SUBJECT: JAVA PROGRAMMING
SUBJECT CODE :– BSIT:42
PART-A
1. How platform independence is achieved in JAVA ?
Ans:– Java is known as platform-neutral language because Java’s byte codes are designed to be read, interpreted, and executed in exactly the same manner on any computer hardware or operating system that supports a Java run-time.
2. list any three features of JAVA.
Ans.:- The Features of JAVA
1) Simple
2) Object-Oriented
3) Distributed
3. What is Java C, Javadoc and Jdbc?
Ans. :- Java C – JavaC is a compiler translates java source code to byte code.
Javadoc – Javadoc is used for creates html format documentation from java source file.
Jdbc – A programming interface that lets Java applications access a database via the SQL language. Since Java interpreters (Java Virtual Machines) are available for all major client platforms, this allows a platform-independent database application to be
written.
4. List different features of OOP.
Ans :- The features of OOP.
1) Objects and classes
2) Abstraction
3) Encapsulation
4) Information hiding
5) Inheritance
6) Polymorphism
5. Name different types of Java tokens.
Ans. :- The different types of Java tokens are :-
1) Reserved Keywords
2) Identifiers
3) Literals
4) Operators
6. What is the task of the main method in Java program ?
Ans.:- After we specify the keywords for declaring the main() method, you specify a String array as parameter of the main() method. The String array represents command line arguments. It is compulsory for a user to specify the parameter to the main() method in all Java programs unlike in C and C++.
For example,
Class class1
{
public static void main (String args[])
{
System.out.println (“Hello”)
}
}
7. Why can?t we use a keyword as a variable name ?
Ans.:- Keywords are an essential part of a language definition. They implement specific features of the language. Java language has reserved 60 words as keywords. These keywords have specific meaning in Java, so you cannot use them as names for variables.
8. Why main method in Java is declared as static ?
Ans.:- The keyword static helps to specify that the main() method can be called without instantiating an object of a class. This is necessary because the main() method is called by the Java interpreter before any objects are created.
public static void main (String args[])
{//code}
After specifying the keyword static, you specify the void keyword. This keyword indicates to the compiler that, the main() method does not return a value.
9. Write an equivalence of switch statement and if statement.
Ans.:- equivalence of switch statement is if and the equivalence of if statement is if else.
10. Constructor is_____________.
Ans.:- used to initialize the objects of the class and has the same name as that of its class.
PART – B
1. a) What is inheritance and how one can achieve code reusability? Explain
with an example.
Ans.:-Inheritance in object oriented programming means that a class of objects can inherit properties from another class of objects. When Inheritance occurs, one class is then referred to as the „parent class? or super class? or „base class?.
Inheritance is an important concept since it allows reuse of class definition without requiring major code changes, inheritance can mean just reusing code , or can mean that you have used a whole class of object with all its variables and functions
For ex, the bike is a part of the class two wheelers, which is again a part of the vehicle as:
Vehicle
Attributes:
Model:
Make
Two Wheeler
Attributes:
No. of wheels
Four Wheeler
Attributes:
No. of wheels
Bike
Attributes:
Scooter
Attributes:
Car
Attributes
Van
Attributes
b) What is a class? How does it accomplish data hiding? Explain with example.
Ans.:- Class is a template that defines a particular type of object. Classes contain all the features of a particular set of objects. We can use the class definition to create objects of that of class type, that is, to create objects that incorporate all the features belonging to that class.
Each object of the class will have its own copy of each of the instance variables that appear in the class definition. Each object will have its own values for each instance variable. The name ‘instance variable’ originates from the fact that an object is an ‘instance’ or an occurrence of a class and the values stored in the instance variables for the object differentiate the object from others of the same class type. An instance variable is declared within the class definition in the usual way, with a type name and a variable name, and can have an initial value specified.
A given class will only have one copy of each of its class variables, and these will be shared between all the objects of the class. The class variables exist even if no objects of the class have been created. They belong to the class, and they can be referenced by any object or class, and not just instances of that class.
Ex:- we might define a motorcycle class that describes the features of all motorcycles . the motorcycle class serves as an abstract model for the concept of a motorcycle-to interact with each type of motorcycle,we should have a concrete instance of that motorcycle.
2. a) Compare in terms of their functions and semantics the following pairs of
statements:
i) do while and while
Ans.:- The difference between the do-while statement and the while statement is that in the while statement, the loop body is executed only when the condition stated in the statement is true. In the do-while loop, the loop body is executed at least once, regardless of the condition evaluating to true or false. The while loop is also called the top tested loop whereas the do-while loop is also called the bottom tested loop.
ii) while and for
Ans.:- In the for loop, three sections, initialization, test condition and increment/decrement are placed in the same line whereas in the while loop, all three sections are placed in three different places in a program. In the for loop, more than one variable can be initialized, tested and incremented at a time.
iii) nested if and switch
Ans.:-The difference between nested if and switch statement is if allows complex expressions in the condition while switch wants a constant we can’t accidentally forget the break between ifs but you can forget the else (especially during cut’n’paste) switch is usually more compact than lots of nested if else and therefore, more readable If you omit the break between two switch cases, you can fall through to the next case in many C-like languages. With if else you’d need a go to (which is not very nice to your readers … if the language supports go to at all.
iv) break and continue.
Ans.:- The continue statement stops the current iteration of a loop and immediately starts the next iteration of the same loop. When the current iteration of a loop stops, the statements after the continue statement in the loop are not executed. The break statement immediately terminates the loop, bypassing the conditional expression and any remaining code in the body of the loop. When a break statement is encountered inside the loop, the loop is terminated and program control resumes the next statement following the loop.
b) Write a program to find sum of the following harmonic series for a given value
of n 1+ 1/2 + 1/3 + . . . .+ 1/n.
Ans.:- public class Series
{
double total;
public void calculate(int n)
{
for(double ctr=1;ctr<=n;ctr++)
{
total=total+1/ctr;
}
System.out.println(“Sum of harmonic series: “+total);
}
public static void main(String a[])
{
Series object=new Series();
int num=Integer.parseInt(a[0]);
object.calculate(num);
}
}
3. a) Explain different data types in Java with example.
Ans.:- DATA TYPES IN JAVA
byte: It is the smallest integer type. This is a signed 8-bit type and has a range from -128 to 127. For example, the following declaration declares two variables B and C of type byte.
byte b,c;
b =2;
c = -114;
short: It is a signed 16-bit type and has a range from -32,768 to 32,767. For example, the following declaration declares variable K of type short.
short k;
k = 2;
int: It is a signed 32-bit type and has a range from -2,147,483,648 to 2,147,483,647.
For example,
int x = 10;
int j = 98;
long: This is signed 64-bit type and has a range from -263 to 263 -1.
For example,
long ds = 1000;
long se;
se =ds * 24 * 60 * 60;
double: It uses 64 bits to store a value.
For example,
double P, R;
P = 10.8;
R =3.14215;
float: It uses 32 bits to store a value.
For example,
float x;
x = -1111;
int : It uses 32 bits to store a value.
For example,
Int score;
Score=90;
char: this data type is used to store characters. It is 16-bit type and has a range from 0 to 65,536.
For example,
char c1,c2;
c1 =84;
c2 =’g';
boolean: it can have only one of two possible values, true or false.
For example,
boolean flag;
flag= false;
b) Describe the structure of a typical Java program.
Ans. :- A Java program may contain many classes of which only one class defines a main method. Classes contain data members and methods. Methods of a class operate on the data members of the class. Methods may contain data type declarations and executable statements. To write a Java program, we first define classes and then put them together.
A Java program may contain one or more sections as shown in the following figure:
Documentation Section
Suggested
Package Statement
Optional
Import Statements
Optional
Interface Statements
Optional
Class Definitions
Essential
Main Method class
{
Main Method Definition
}
Essential
General Structure Of a Java program
Documentation Section
The documentation section comprises a set of comment lines giving the name of the program, the author and other details. Java also uses the comment /**…*/ known as documentation comment.
Package Statement
The first statement allowed in a Java file is a package statement. This statement declares a package name and informs the compiler that the classes defined here belong to this package.
Example: package student;
Import Statement
The next thing after a package statement (but before any class definitions) may be a number of import statements. This is similar to the #include statement in C++. Example:
import student.test;
This statement instructs the interpreter to load the test class contained in the package student.
Interface Statements
An interface is like a class but includes a group of method declarations. This is also an optional section and is used only when we wish to implement the multiple inheritance feature in the program.
Class Definitions
A Java program may contain multiple class definitions. Classes are the primary and essential elements of a Java program.
4. a) What is JVM ? How does it help to achieve platform independence? If JVM is
available for windows then can we run program written on Unix platform ?
Comment.
Ans.:-Java compiler produces an intermediate code known as byte code for a machine that does not exist . this machine is called JAVA VIRTUAL MACHINE (JVM). . Java is known as platform-neutral language because Java’s byte codes are designed to be read, interpreted, and executed in exactly the same manner on any computer hardware or operating system that supports a Java run-time.
Yes. One of the fundamental principles of Java is “write once, run anywhere.” This means that Java source code can run on any platform for which a JVM exists, regardless of where the original code was developed
b) How are data and method organized in an object oriented program ? Illustrate
the same for car object.
Ans.:- In an object-oriented program, a set of variables and functions used to describe an object constitutes a “class”.
A class defines the structure and behavior (data and method) that will be shared by a set of objects. Each object of a given class contains the structure and behavior defined by the class, as if it were stamped out of a mould in the shape of a class. A class is a logical construct. An object has physical reality. When we create a class, you will specify the code and data that will constitute that class. Collectively, these elements are called the members of the class. Specifically, the data defined by the class are referred to as member variables or instance variables. The code that operates on that data is referred to as member methods or just methods, which define the use of the member variables.
5. a) Distinguish between the following terms:
i) Dynamic binding and message passing.
Ans.:- Dynamic binding in java is the mechanism by which compiler cannot determine which method implementation to use in advance. Based on the class of the object, the runtime system selects the appropriate method at runtime. Dynamic binding is also needed when the compiler determines that there is more than one possible method that can be executed by a particular call.
Java’s program units, classes, are loaded dynamically (when needed) by the Java run-time system. Loaded classes are then dynamically linked with existing classes to form an integrated unit. The lengthy link-and-load step required by third-generation programming languages is eliminated.
Message Passing: In an object based world the only way for anything to happen is by objects communicating with each other and acting on the results. This communication is called message passing and involves one object sending a message to another and (possibly) receiving a result.
ii) Inheritance and polymorphism.
Ans.:- Inheritance in object-oriented programming means that a class of objects can inherit properties from another class of objects. When inheritance occurs, one class is then referred as the ‘parent class’ or ‘super class’ or ‘base class’. In turn, these serve as a pattern for a ‘derived class’ or ‘subclass’.
Inheritance is an important concept since it allows reuse of class definition without requiring major code changes. Inheritance can mean just reusing code, or can mean that you have used a whole class of object with all its variables and functions.
Polymorphism: It is a key concept in object-oriented programming. Poly means many, morph means change (or ‘form’).
Polymorphism is simply a name given to an action that is performed by similar objects. Polymorphism allows a common data-gathering message to be sent to each class and allows each subclass object to respond to a message format in an appropriate manner to its own properties. Polymorphism encourages something we call ‘extendibility’. In other words, an object or a class can have its uses extended.
b) What are the difference between C and Java ?How Java and C++ are similar?
Ans.:-
6. a) Define programming. What are the types of programming? Explain.
Ans.:- Programming:- a programming is a specific set of ordered operations for a computer to perform .
UNSTRUCTURED PROGRAMMING
In an unstructured programming the main program directly operates on global data.
PROCEDURAL PROGRAMMING
With procedural programming we are able to combine returning sequence of statements into one single place . a procedure call is used to invoke the procedure.
MODULAR PROGRAMMING
With modular programming procedures of a common functionality are grouped together into separate modules. A program therefore no longer consists of only one single part.
OBJECT-ORIENTED PROGRAMMING
In object oriented programming, a complex system is decomposed in accordance to the key abstractions of the problem.
It is a method of implementation in which programs are organized as co-operative collection of objects, each of which representation an instance of some class and whose classes all members of a hierarchy of classes united in inheritance relationships.
b) Explain bitwise operators in Java with example.
Ans.:- BITWISE OPERATORS
SHIFT AND LOGICAL OPERATORS
A shift operator allows you to perform bit manipulation on data.
OPERATOR
USE
OPERATION
>>
Op1 >> op2
Shift bits of op1 right by distance op2
<<
Op1 << op2
Shift bits of op1 left by distance op2
>>>
Op1>>> op2
Shift bits of op1 right by distance op2
Each shift operator shifts the bits of the left-hand operand over by the number of positions indicated by the right- hand operand.
Ex. – 13 >> 1
The binary representation of the number 13 is 1101. The result of the shift operations is 1101 shifted to the right by one position -1106 or 6 in decimal.
The java programming language also provides these four operators that perform logical functions on their operands :-
OPERATOR
USE
OPERATION
&
Op1 & op2
Bitwise and
|
Op1 | op2
Bitwise or
^
Op1 ^ op2
Bitwise x or
~
Op1 ~ op2
Bitwise complement
The & operation performs the logical “and” function on each parallel pair of bits in each operand . the “and” function sets the resulting bit of 1 if both operands are 1 .
Op1
Op2
RESULT
0
0
0
0
0
0
1
0
0
1
1
1
Suppose we were to “and” the values 12 and 13
12 & 13
The result of this operation is 12. Because the binary representation of 13 is 1101. The “and” function sets the resulting bit to 1 if both to 1 if both operand bits are 1, otherwise, the resulting bit is 0.
7. a) List and explain different types of loops in Java.
Ans. :- Loops in java
(I) While loop
(II) Do loop
(III) For loop , continue and break statement
THE WHILE LOOP
The while statement contains a condition and a loop body. the condition is enclosed within parentheses.
All the variables used in the condition of the while statement must be initialized before the while loop. The values of the variables used in the condition must be changed in the loop body. Otherwise, the condition may always remain true and the loop may never terminate.
Syntax:
While (test condition)
{
Body of the loop
True
};
Condition
Statement
Ex.-
Class numbers
{
Public state void main(String args[])
{
Int n = 0 ;
Int num = 5;
While (n <= num)
{
System.out.println(n);
N++
}
}
}
DO STATEMENT
Similar to the while statement, the do-while statement is a lopp statement provided by java. The statement helps to perform certain repetitive actions depending on a condition.
The major difference between the do-while statement and the while statement is that in the while statement, the loop body is executed only when the condition stated in the statement is true.
We can use the do-while loop in situations where an action must be performed at least once without evaluating the condition.
Program to print the numbers from 1 to 5
Class numbers
{
Public static void main (string args[])
{
Syntax:
While (test condition)
{
do
Body of the loop
};
False True
While
Condition
Statement
Int n=0;
Int num = 5;
Do
{
System.out.println(n);
N++;
}
While(n<=5);
}
}
FOR STATEMENTS
To manage iterative actions, java provides the for statement as an efficient alternative to the while statement. The statement creates to loop in which a set of statements is repeatedly executed until the specified condition becomes false.
The syntax of the for statement is
For(initialization expression; test condition; update expressions)
{
Statement1;
Statement2;
}
The for statement starts with the for keyword.
b) What is polymorphism? Explain method overriding with example and prove
that it is a polymorphism.
Ans.:- Polymorphism (from the Greek, meaning “many forms”) is a feature that allows one interface to be used for a general class of actions. The specific action is determined by the exact nature of the situation.
Ex.- a stack (which is a last-in, first-out list). You might have a program that requires three types of stacks. One stack is used for integer values, one for floating-point values, and one for characters.
METHOD OVERRIDING
In the class hierarchy, when a method in a subclass has the same name and type signature as method
in the superclass, then the method in the subclass is said to override the method in superclass.
class Book { //super class defined
String name = “JAVA PROGRAMMING” ;
int id = “34567”;
void show ( ) {
System.out.println( “Book name is “ +name);
System.out.println( “Book id is “ +id);
}
}
Save this file as book.java and compile. This is our Base Class
class Book1 extends Book { // This is the subclass
String author = “micheal janson”;
void show ( ) {
System.out.println( “Book name is “ +name);
System.out.println( “Book id is “ +id);
System.out.println( “The author name is “ +author);
}
public static void main(String args[ ] ) {
Book1 x = new Book1( );
x.show();
}
}
8. a) What is a parameterized constructor? Explain its usage with an example.
Ans:- A parameterized constructor in java is just a constructor which take some kind of parameter (variable) when is invoked.
For example.
class MyClass
{
//this is a normal constructor public MyClass()
{
//do something
}
//this is a parameterized constructor public MyClass(int var)
{
//do something
}
//this is another parameterized constructor public MyClass(String var, Integer var2){ //do something } }
b) Explain the methods
(i) Trim
Ans. :- The trim method returns a copy of the invoking string from which any leading and trailing white space has been removed. It has the general form
String trim ( );
class altStr{
public static void main (String args[ ]) {
String str = “Hello”;
String str2 = “Java”;
str = str.toUpperCase();
str2 = str2.toLowerCase();
System.out.println (str); // HELLO
System.out.println (str2);// java
str = str.concat(str2); // str now equals “HELLO java”
System.out.println (str);
str = str.trim(); // str now equals “HELLOjava”
System.out.println (str);
str = str.substring (5,str.length()); // str = “java”
System.out.println (str);
str = str.replace (‘a’, ‘i’); // str = “jivi”
System.out.println (str);
}
}
ii) substring
The subString method is used to create new instances of the class String from existing instances. The new string is specified by giving the required index range within the existing string.
String substring(int startIndex)
This returns the sub string that starts at startIndex and runs to the end of the invoking string.
String substring(int start Index, int endIndex)
This returns the substring that starts at startindex and runs through endIndex-1;
iii) length
The length of a string is the number of characters that it contains. To obtain this value call a length method.
int length();
class strCmp {
public static void main (String args[ ]) {
String str = “Hello”;
String str2 = “Java”;
System.out.println (str.equals(str2)); // false
System.out.println (str.compareTo(str2)); // a negative number,
i.e. str is less than str2
System.out.println (str.charAt(0)); // H, i.e. char is position 0
System.out.println (str.length() + str2.length()); // 5 + 4 = 9
}
}
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