Introduction to java

Introduction TO JAVA
Rishi Ram Khanal
BIM(TU)

History of Java
Java was developed by James Gosling at Sun
Microsoftsystem and it was originated at Sun
Microsystem in 1991

JAVA is Everywhere
Java resides in mobiles,client machines,sever
machine,embedded device,smart phones,
cloud etc.
It shares the same basic features of the
language and libraries
Principle of java:write once,Run
anywhere(WORA)

What is Library?
Java Library is a collection of predefined
classes.
You can use these classes either by inheriting
them or by instantiating them.
JAVA flavours
Java se(core java)
Java EE (Advance java)
Java ME(Mobile Edition for java)

Version History Of JAVA
Version NO of classes NO of package
Java 1.0 212 8
Java 1.1 503 23
Java 2 1520 29
Java 5 3562 166
Java 6 3792 203
Java 7 4024 209

Features of JAVA
Simple
Object oriented Language
Distributed
Interpreted
Robust
Secure
Portable
Multi-threaded
Garbage Collector

Installation of Java
How to Compile?
Hello.java Hello.class
How to Run
Hello.class
OS
Interpreter(just-in-time compiler)

Installation and setup
• http://www.oracle.com/technetwork/java/javase
/downloads/jdk8-downloads-2133151.html
• After installation we will see a java folder where u
install the java.Inside java folder we will see two
folder
• Jdk: java development Kit used for to write java
program
• Jre:Java Runtime Enviroment used for to run the
java files

JDK and JRE
Java Development Kit contains tools needed
to develop the java programs
These tools could be
compiler(javac.exe),Application
Launcher(java.exe) etc
Jre: Java Runtime Environment
It contains JVM(java Virtual Machine) and java
Package classes(java Library)

JVM
JVM is platform dependent
The java Virtual Machine provides a platform
–independent way of executing code
Java Virtual Machine Interprets the bytecode
Into machine code depending upon the
underlying operating system and hardware
combination

First Program JAVA
Remember
• Java is a case sensitive language like c and c++
• Java is nearly 100% object oriented language
• In java, it is possible to make a function which
is not a member of any class(as we can do in c
and C++)

First Program
Public class HelloWorld
{
public static void main(String args[])
{
System.out.println(“HelloWOrld”);
}
}

FOR pratical
• Write a program in notepad and save in bin
folder of jdk Compile and run the program
Delete the file from bin folder and make another
program in notepad and save in Desktop and
compile and run the program and please note
the error u got and how u solve the error

DataTypes and Keywords In java
 Java Identifiers
All the java components require names.Names used for
classes, variables and method are called identifiers.In java ,
there are several points to remember about identifiers.
• All identifiers should begin with a letter (A to Z or a to z),
currency character ($) or an underscore (_).
• After the first character, identifiers can have any combination
of characters.
• A keyword cannot be used as an identifier.
• Most importantly identifiers are case sensitive.
• Examples of legal identifiers:age, $salary, _value, __1_value
• Examples of illegal identifiers: 123abc, -salary

Java Keywords
• These reserved words may not be used as constant or variable or any other identifier
names.

Literals, Comments,Separators
Literals
A literal is a source code representation of a fixed value. They are
represented directly in the code without any computation.
Comments
Java supports single-line and multi-line comments very similar to c and
c++. All characters available inside any comment are ignored by Java
compiler.
/* This is my first java program.
This will print 'Hello World' as the output
This is an example of multi-line comments. */
// This is an example of single line comment /* This is also an example of
single line comment. */

Details about Literals
Literals can be assigned to any primitive type variable. For example:
byte a =68;
char a ='A'
byte, int, long, and short can be expressed in decimal(
base 10),hexadecimal(base 16) or octal(base 8) number systems as well.
Prefix 0 is used to indicate octal and prefix 0x indicates hexadecimal when
using these number systems for literals. For example:
int decimal=100;
int octal =0144;
int hexa =0x64;
String literals in Java are specified like they are in most other languages by
enclosing a sequence of characters between a pair of double quotes.
String and char types of literals can contain any Unicode characters. For
example:
char a ='u0001'; String a ="u0001";

Variable
• In Java, all variables must be declared before they
can be used. The basic form of a variable
declaration is shown here:
type identifier [= value][, identifier [= value]...];
int a, b, c;// declares three ints, a, b, and c.
int d =3, e, f =5;// declares three more ints,
initializing // d and f.
byte z =22;// initializes z.
double pi =3.14159;// declares an approximation of
pi.
char x ='x';// the variable x has the value 'x'.

• This chapter will explain various variable types
available in Java Language. There are three
kinds of variables in Java:
• Local variables
• Instance variables
• Class/static variables

TYPECASTING in JAVA
Impicit Type Casting
Explicit Type Casting
SCANNER OBJECT
ARRAYS

ARRAY
• Declaring Array Variables:
To use an array in a program, you must declare a variable to
reference the array, and you must specify the type of array the variable
can reference. Here is the syntax for declaring an array variable:
dataType[] arrayRefVar; // preferred way.
or
dataType arrayRefVar[]; // works but not preferred way.
Example:
• The following code snippets are examples of this syntax:
double[] myList; // preferred way.
or
• double myList[]; // works but not preferred way.

Creating ARRAY
• You can create an array by using the new operator with the following
syntax:
• arrayRefVar = new dataType[arraySize];
• The above statement does two things:
• It creates an array using new dataType[arraySize];
• It assigns the reference of the newly created array to the variable
arrayRefVar.
• Declaring an array variable, creating an array, and assigning the reference
of the array to the variable can be combined in one statement, as shown
below:
• dataType[] arrayRefVar = new dataType[arraySize];
• Alternatively you can create arrays as follows:
• dataType[] arrayRefVar = {value0, value1, ..., valuek};
• The array elements are accessed through the index. Array indices are 0-
based; that is, they start from 0 to arrayRefVar.length-1.

• Following statement declares an array variable, myList,
creates an array of 10 elements of double type and assigns its
reference to myList:
• double[] myList = new double[10];
• Following picture represents array myList. Here, myList holds
ten double values and the indices are from 0 to 9.

The foreach Loops:
• JDK 1.5 introduced a new for loop known as
foreach loop or enhanced for loop, which
enables you to traverse the complete array
sequentially without using an index variable.
• SCANNER OBJECT

PRACTICAL
• TypeCasting Problem
• Declare an array whose size is 5 .Process the
array and Print all the elements of array and
find total sum of all elements and Find
greatest number from that element
• Implement foreach Loop
• Create a class , take the two input from
keyboard and sum two number and process
the array by using Scanner

Introduction to java

Recommended

More Related Content

What's hot (20)

Similar to Introduction to java (20)

More from rishi ram khanal (20)

Recently uploaded (20)

Introduction to java