2. ObjectObject
An object is anything that can be represented by
data in a computer’s memory and manipulated by
a computer program.
Numbers, texts, pictures, sound, video ….. So on
3. ObjectObject
An object can be something in the physical world or even just an abstract idea.
for example: An airplane, is a physical
object that can be manipulated by a
computer.
4. ObjectObject
A bank transaction is an example of an object that is not physical.
To a computer,
an object is simply something that can be represented by data in the
computer’s memory and manipulated by computer programs
5. ObjectObject
The data that represent the
object are organized into a
set of properties.
NameName:: AI 379AI 379
OwnerOwner:: Indian AirlinesIndian Airlines
LocationLocation:: 39 52′ 06″N39 52′ 06″N 75 13′ 52″W75 13′ 52″W
HeadingHeading:: 271271°°
AltitudeAltitude:: 19 m19 m
AirSpeedAirSpeed:: 00
MakeMake:: BoeingBoeing
ModelModel:: 737737
WeightWeight:: 32,820 kg32,820 kg
The values stored in an
object’s properties, at any
one time, form the state
of an object.
10. ObjectObject--Oriented ProgrammingOriented Programming
A class can be thought of as a blueprint for
instances of its object.
Two different instances of the same class will
have the same properties, but different values
stored in those properties.
13. Development tools-part of java development kit (JDK)
Classes and methods-part of Java Standard Library (JSL),
also known as Application Programming Interface (API)
1. JDK:
Appletviewer ( for viewing applets)
Javac (Compiler)
Java (Interpreter)
Javah (for C header files)
Javadoc ( for creating HTML description)
Java Environment
14. 2. Application Package Interface (API)
Contains hundreds of classes and methods grouped into several
functional packages:
Language Support Package (String, Integer, Double, etc)
Utility Packages (rand. num. gen., sys. date)
Input/Output Packages
Networking Packages (implementing networking appl. )
AWT Package (classes for painting graphics and images)
Applet Package (web page using java)
Java Environment
15. 1. Java 1.0 (96)
2. Java 1.1 (97)(Add new library, redefine applet handling and
reconfigured many features.)
3. Java 2 (98)(Second generation). Version no:1.2 (Internal
version number of java library). Also known as J2SE [ Java
2 Platform Standard Edition].
- Add swing, the collection framework, enhanced JVM etc.
4. J2SE 1.3 (2000)
5. J2SE 1.4 (2002)
6. J2SE 1.5 (2004)
7. J2SE 1.6 (2006) [1.7-(2013), in queue 1.8 (exp in 2014) ]
The Evolution of Java
16. Comments
In Java, comments are preceded by two slashes (//) in a
line, or
enclosed between /* and */ in one or multiple lines
When the compiler sees //, it ignores all text after // in the
same line
When it sees /*, it scans for the next */ and ignores any text
between /* and */
17. Example
/* Traditional "Hello World!" program. */
// package pack1;
// import java.lang.System;
class A
{
public static void main (String args[])
{
System.out.println("Hello World!");
}
}
Save program as A.java
18. Java Program Structure
Package Statement
Javac command compiles the source code A.java then,
generates A.class and store it under a directory which is
called as name of the package
package statement if used must be the first statement in
a compilation unit. Its syntax is:
package packageName;
For example:
package pack1;
19. Import Statement
The import statements are similar to #include
statements in C and C++
In the above program, System class of java.lang package
is imported into all Java programs by default. The
syntax of import statement is as:
import fullClassName;
For example, the following import statement imports the
System class from java.lang:
import java.lang.System;
import java.lang.*;
20. Classes and Methods
Class declarations contain a keyword class and an identifier (Ex: A)
Class members are enclosed within braces. The syntax of defining a
class is shown below:
class A
{
// program code
}
To execute a class, it must contain a valid main method
It is the first method that automatically gets invoked when the program
executed
public static void main (String args[])
{
//instructions
}
