Lecture1_Introduction.ppt

PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR
Core Java Proggramming
Java Language Features

Java language was developed by company Sun
Microsystems and creator is James Gosling

JAVA introduction:-
Author James Gosling
Vendor Sun Micro System
Project name Green Project
Type open source & free software
Initial OAK language
Present Name java
Extensions .java & .class & .jar
Initial version jdk 1.0 (java development kit)
Present version java 8
Operating System multi Operating System
Implementation Lang c, cpp……
Symbol coffee cup with saucer
SUN Stanford Universally Network
Slogan/Motto WORA (write once run anywhere)

Features of Java Language
• Simplicity
• Object Oriented
• Platform Independent
• Distributed
• Robust & Secure
• Multi-Threaded
• Compiled and Interpreted

Compiled & Interpreted…
• Java programs are executed by an interpreter, so
it’s relatively easy to find errors in a program.
• When a running program encounters a problem,
the Java interpreter will display a meaningful
message and , if necessary stop the program.

Compiled & Interpreted…
Machine Code
Windows
Interpreter
Macintosh
Interpreter
Machine Code
Windows
Computer
Windows
Computer
Source Code
Java Compiler
Byte code
Implementation of
Java Program

Java Architecture…
• The Java Language and run time environment were
designed to facilitate network computing.
• The java design team wanted java to be able to create
flexible and highly reliable programs that could be
distributed across networks and run on virtually any
computing platform. Java stores source code files as ASCII
text files. Java source files are later compiled to Byte -
code file.

Bytecode…
• Byte-code is a standardized machine independent,
low level language. The byte code files are loaded
and interpreted at the client’s machine by a special
program called Java Virtual Machine(JVM).
• For Example : An HTML document downloaded to
your machine by a browser might embed a Java
data entry applet. When we activate this applet,
the byte code files are executed by the browser's
JVM.

Bytecode…
• When a user runs a Java Program , it is upto the
JVM to load, possibly verify and then execute it.
• The JVM can perform this function from within a
browser or any other container program or directly
on top of the operating system.

What actually JVM does...
• It validates the requested byte codes verifying that
they pass various formatting and security checks.
This is a security feature known as
Byte-code-verifier.
• It allocates memory for the incoming Java class
files and guarantees that the security of JVM is not
violated. This is known as class loader.
• It interprets the byte-code instructions found in
the class files to execute the program.

Java Development Kit...
• The JDK comes with a collection of tools that are
used for developing and running Java Programs.
• appletviewer (for viewing Java applets)
• javac (Java compiler)
• java (Java Interpreter)
• javap ( Java diassembler)
• javah (for C header files)
• jdb (Java debugger)

Installation of Java
1. First Of all you have a .exe file of Jdk1.7(if not then
download from Oracle Site).
2. Now this exe file can be save anywhere (let us consider
D: drive)
3. Open d: drive and double click on jdk1.7 exe file.
4. Press Next button until complete.
5. Now check where java is installed in your machine.
6. If java is successfully installed it means the path where
java is installed should be(default path):
7. C:program File(X86)javajdk1.7

• Doble click on the java installation exe file

Click Next Button

First Java Application Program...
import java.lang.*;
class Firstapp
{
public static void main(String args[ ])
{
System.out.println(“This is First Application”);
}
}

• Explanation:
• For most computer languages, the name of file
that holds the source code to a program is
arbitrary. However this is not the case with Java.
The first thing you must learn about Java is that
the name you give to a source file should match
the name of the class holds the main() method. So,
in our case name of program is none other than
Firstapp.java. This is because the source file is
officially called a compilation unit. Extension is
also four character long, so your OS must support
long extensions.

Explanation:
First statement import java.lang.*;
The purpose of this statement to instruct
interpreter to load language package lang.
Second statement class Firstapp
Declares a class name firstapp so as to place
everything inside this class.
Third statement public static void main(String args[ ])
Defines a method main. This is the starting point for

• the interpreter to begin the execution of program.
Here public is an access specifier that declares the
main method as unprotected and therefore making it
accessible to all other classes.
• Next appears the keyword static which declares
this method as one that belongs to the entire class
and not a part of any objects of the class. The main
must always be declared as static since the interpreter
uses this method before any objects are created. The
type modifier void states that main method does not
return any value.

• In main(), there is only one parameter String args[ ]
• declared a parameter named args, which is an
array of objects of the class String. Objects of type
String store character strings. args receives any
command-line arguments present when the
program is executed. This program does not make
use of this information.

• Fourth statement is
System.out.println(“This is First Application”);
• The println mehtod is a member of the out object,
which is a static data member of System class. This
line prints the string to the screen. The method
println always appends a newline character to the
end of the string. So for the output to be printed
on the same line use print in place of println.

• To compile the Java program, execute the compiler, javac,
specifying the name of the source file on command line:
• C:> javac Firstapp.java
• The javac compiler creates a file called
Firstapp.class that contains the bytecode version
of the program. The bytecode is the intermediate
representation of your program that contains
instructions the Java Interpreter will execute. So,
to run your program you use Java interpreter java.
• C:> java Firstapp

• When Java source code is compiled each
individual class is put its own output file named
after the class and using the .class extension. This
is why it is important to give source the same
name as the class they contain, so when you
execute your program you are actually executing
the class by the interpreter. It will automatically
search for a file by that name that has the .class
extension. If it finds the file, it will execute the
code contained in the specified class.

Eclipse IDE(LUNA Version)
1.First Of All you should be download Eclipse
Luna Version and paste Zip format anywhere
(Suppose D: drive )

• Now Extract this zip Folder in same here
like…..

• Now DoubleClick on eclipse folder and
search eclipse.exe
• DoubleClick on eclipse icon(.exe)

• Select the workspace

• Now How to java Program run
• Go to File->Java Project

• Now provide the name of Project

• Click Next Button

• Now click on finish button
• See the project Test of Left Pane and Expand
this

• Now right click on “src” folder select New-
>Class

• Provide the class name we provide “Hello”

• Write the code on Hello Class File Like

• Now right Click On Hello.java select RunAs-
>Java Application

Lecture1_Introduction.ppt

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