Chapter 9 – Introduction
to Java
Answer the following questions.
1)
What is OOP?
OOP’s means
Object-Oriented Programming.
OOP’s is a methodology
that focuses on data items rather than processes.
It’s bridge between
problem in the real world and solution in computer programming.
In this a programmer can
focus on the objects that naturally make up a system, rather than its
procedure.
Or
Object means a real
word entity such as pen, chair, table etc.
Object-Oriented
Programming is a methodology to design a program using classes and
objects.
It simplifies the software
development and maintenance by providing some concepts like
It’s based on
1) Object 2) Class 3)
Encapsulation 4) Inheritance
2)
What is Object?
Object
means collection of data and the procedure or function
which
work on that data.
There
are two main characteristics of an object
Or
Object means
a real word entity such as pen, chair, table etc
1)
State/Attributes
2)
Behaviour/Actions.
Example:
Car,Pencil,etc..
3)
What is Class?
A
Class defines a type of object.
It
defines the variables and methods common to all object of a certain kind
It
also describes the rules by which objects behave.
Or
A
class is a collection of objects of similar types.
Example: mango, apple, and orange are members of the
class fruit.
Class
is user-defined data types and behaves like the built –in types of language.
4)
What is Encapsulation?
Encapsulation is the
process of keeping the data of an object along with its methods and hiding it
from the outside world.
Or
‘‘ The wrapping
up of data
and methods into a single unit (called class) is known
as Encapsulation ’’
Example:
Common illustrations:
Ø The internal organs,
muscles, bones etc. of human body is encapsulated with Skin.
Ø A chocolate is encapsulated with a wrapper.
In Encapsulation
An object is composed of a
public and private section.
Public section is the one
that can be accessed from outside the object.
Private section is the one
that can’t be accessed from outside the object.
5)
What is Inheritance?
|
Sub
Class
|
|
Super
Class
|
Or
“It is
the process by
which one object
acquires the properties
(attributes & actions) of
another object”.
6)
Steps to create a New Project
in BlueJ?
1)
Click
on Project menu -> select New Project option
2)
Select
location and specify the name of project. Like “StudentProject”.
and then click on Create
button.
3)
Then
you can see Project window & one README.TXT file.
4)
Click
on README.TXT and write down the following details:
a. PROJECT TITLE: d. PURPOSE OF PROJECT:
b. VERSION or DATE: e. HOW TO START THIS PROJECT:
c. AUTHORS: f. USER INSTRUCTIONS:
7)
Steps to create a class in
BlueJ?
After
creating a project to create a class follow these steps:
1)
Click
on New Class
2)
Then
write down class name & select the type of class.
3)
Now
right click on that class select Open Editor and after removing given code
write your own code.
4)
Then
compile that class. If it is done successfully the slanting bar s will
disappear else it gives you an error.
8)
What is Compiler?
Compiler
is a process of transforming source code into object code for execution.
9)
What is Variables? Types
of variable in Java.
A
variable refers to the memory location that holds values like:
Number,
Texts, etc. in computer memory.
There
are three types of variables in java:
1) Instance Variable -
It is related to objects
of a class and each object of the same class can have different instance
variables.
2) Class Variable -
It is related to class and
not to particular objects of a class.
It is define with static
keyword and shared by all object of that class.
It is like global variable
which are same for all objects of the class.
3) Local Variable -
The variable which are defined
in a method or block of code.
10)
State the rules for naming a variable in java.
i)
Uppercase and lowercase letters are different.
ii)
No limitation to the number of letters in a
variable name
iii) Digits
are allowed but the first letter must be an alphabet.
iv) Only ‘$’
and ‘_’ are allowed in a variable ‘$’ cannot appear in the beginning.
v)
Spaces are not allowed.
11)
What is Data Type?
The type of value that a
variable can hold is called data type.
When we declare a variable
we need to specify the type of value it will hold along with the name of
variable. Like..
12)
Give Example: How to
declare and initialize the variable in java?
Example of declaring the
variable:
int
Num;
here variable name is Num and the data type is int
so it can store integer value.
float
num;
char
Name;
double
Math;
Example of initializing the variable:
The value can be given to
the variable when they created. Like.
float Eng=89;
int age=13;
char Alpha=’A’;
13)
How to handle flow of a
data?
Ø System.out.println()
–
used to display the output on the computer screen.
Ø System – predefined class to provide
access to the system,
Ø out – it is output stream
Ø println() – function to display the
text(string) passed inside brackets
Ø Ex. System.out.println( “Welcome to Java”)
Ø Ex. int A=10;
Ø System.out.println(“value
of A is : ”+A)
Note:-also refer page no 99 to 101 from text book.
Fill in the blanks
1. int A; A occupies ____2____bytes.
2. float B; B occupies ____4___bytes.
3. double Num; Num occupies ___8____ bytes.
4. char alpha; alpha occupies
____2______bytes.
5.
The
variable which are defined in a method or block of code is called Local
Variable.
6.
The
type of value that a variable can hold is called data type.
7.
println()
is
a function to display the text(string) passed inside brackets.
8.
Compiler is a process of
transforming source code into object code for execution.
9.
A
BlueJ project is a directory
containing raw Java source code files, compiled java files and some additional
files.
Note :-
also
refer text book, text book exercise from cd & worksheet.
chapter 7 material will be uploaded soon.
Computer syllabus for Cycle Test 3 :-
Chapter 7: Understanding CorelDraw
Chapter 9: Introduction to Java
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