java language allows three types of comments
1)single line comments //
2)multiline comments /* ...*/
3)Documentation comments /** .. */
The key
considerations were summed up by the Java team in the following list of
buzzwords:
SIMPLE easy to learn and use
SECURE programs are confined to the Java
execution environment and cannot access other parts of the computer.
PORTABLE
OBJECT-ORIENTED a clean, usable, pragmatic approach to objects, not restricted by the
need for compatibility with other languages.
ROBUST
allow the programmer
check the mistakes early performs compile-time (strong typing) and run-time
(exception-handling) checks, manages memory automatically.
MULTITHREADED writing program that perform concurrent
computations
ARCHITECTURE-NEUTRAL J V M provides a platform independent environment for
the execution of Java byte code
INTERPRETED
compiled into an intermediate byte code
HIGH PERFORMANCE
DISTRIBUTED Java handles TCP/IP protocols, accessing a resource through
its URL much like accessing a local file.
DYNAMIC substantial amounts of run-time type
information to verify and resolve access to objects at run-time.
Data Types
:- Java defines eight simple types:
1)byte –
8-bit integer type
2)short –
16-bit integer type
3)int –
32-bit integer type
4)long –
64-bit integer type
5)float –
32-bit floating-point type
6)double –
64-bit floating-point type
7)char –
symbols in a character set
8)boolean –
logical values true and false
Scope of a
variable:-
A variable
declared inside the scope is not visible outside:
{
int n;
}
n = 1;//
this is illegal
Two styles
of array declaration: type
array-variable[];or type []
array-variable;
Multidimensional
arrays are arrays of arrays:
1)
declaration: int array[][];
2)
creation: int array = new int[2][3];
3)
initialization int array[][] = { {1,
2, 3}, {4, 5, 6} };
bitwise operators
~
|
~op
|
Inverts all bits
|
&
|
op1 & op2
|
Produces 1 bit if both operands are 1
|
|
|
op1 |op2
|
Produces 1 bit if either operand is 1
|
^
|
op1 ^ op2
|
Produces 1 bit if exactly one operand is 1
|
>>
|
op1 >> op2
|
Shifts all bits in op1 right by the value of op2
|
<<
|
op1 << op2
|
Shifts all bits in op1 left by the value of op2
|
A class is a blueprint
that defines the variables and methods common to all objects of a certain kind.
Example: ‘your dog’ is
a object of the class Dog.
An object holds values
for the variables defines in the class.
An object is called an
instance of the Class
Real world objects are
things that have:
Example: your dog:
state – name, color, breed, sits?,
barks?, wages tail?, runs?
behavior – sitting, barking, waging
tail, running
A software object is a
bundle of variables (state) and methods (operations).
A SAMPLE PROGRAM WHICH EXPLAINS THE CONCEPT OF CLASSES AND OBJECTS
import java.io.*;
import java.lang.*;
class
box
{
//INSTANCE OR CLASS VARIABLES
int length;
int breadth;
int height;
//method-1 constructor
box()
{
length=1;
breadth=2;
height=2;
}
//method-2 reading data
void getdata(int l,int b, int h)
{
length=l;
breadth=b;
height=h;
}
//method-3 display the values on the screen
void display()
{
System.out.println("the values of box are "+length+" , "+ breadth+ " , "+height);
}
//method-4 calculation of the volume
void volume()
{
int volume;
volume=length* breadth* height;
System.out.println("the volume is"+volume);
}
}
//SECOND CLASS the above class implementation is done here
public class
boximpl
{
public static void main(String args[])
throws Exception
{
//here we are initilizing the data to the object through constructor
box b=new box();
b.display();
b.volume();
//here we are reassigning values through method which is already done by the constructor
b.getdata(1,2,3);
b.display();
b.volume();
/*now we will consontrate how repeatedly do the volume calculation by taking concern of user each and every iteration this can be done by so many was here i assisted the string class and activating of one of the reader class for user input*/
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String s="yes";
while(s.equals("yes"))
{
System.out.println("WELCOME TO THE NEW ITERATION"+'\n'+'\n');
System.out.println("enter the value for the length");
int l1= Integer.parseInt(br.readLine());
System.out.println("enter the value for the breadth");
int b1= Integer.parseInt(br.readLine());
System.out.println("enter the value for the height");
int h1= Integer.parseInt(br.readLine());
b.getdata(l1,b1,h1);
b.display();
b.volume();
System.out.println("do u wants repetation ");
s=br.readLine();
}
}//end of main()
}//end of
OUTPUT:-
compilation and interpretation
e:\ramu>javac boximpl.java
e:\ramu>java boximpl
The values of box are 1
, 2 , 2
The volume is4
The values of box are 1
, 2 , 3
The volume is6
WELCOME TO THE NEW ITERATION
enter the value for the length
1
Enter the value for the breadth
2
Enter the value for the height
3
The values of box are 1, 2, 3
The volume is6
Do u wants repetition
Yes
Access
Specifiers: An
access specifier is a key word that represents how to access a member
of a class. There are four access
specifiers in java.
private: private members
of a class are not available outside the class.
public: public members
of a class are available anywhere outside the class.
protected: protected members
are available outside the class.
default: if no access
specifier is used then default specifier is used by java compiler.
Default
members are available outside the class.
IN THIS I AM
FRAMING HOW WE WILL PASS OBJECTS AS REFERENCE TO THE SAME CLASS ANOTHER OBJECT
METHOD
class
Complex
{
private int
real,imag;
public void
Complex(int x,int y)
{
real=x;
imag=y;
}
Complex()
{
real=10;
imag=20;
}
public void
Complex(int x)
{
real=x;
}
public void
display()
{
System.out.println(+real+"i"+imag);
}
public void
add(Complex c1, Complex c2)
{
real=c1.real+c2.real;
imag=c1.imag+c2.imag;
}}
class ramu
{
public
static void main(String args[])
{
Complex c1 = new Complex();
Complex c2 =
new Complex();
Complex c3 =
new Complex();
c1.display();
c2.display();
c3.display();
c1.Complex(1,2);
c2.Complex(2,3);
c1.display();
c2.display();
//here I am
passing to the same class object references two the third class object method
add()
c3.add(c1,c2);
c3.display();
}}
STRING CLASS
String strOb1 =
"First String";
String strOb2 =
"Second String";
String strOb3 =
strOb1;
strOb1.length();
strOb1.charAt(3);
if(strOb1.equals(strOb2))
String myString =
"I" + " like " + "Java."; //in this + string operator concatenation variable contains ilikejava
