IMPLEMENTATION OF MEHTOD OVERLOADING

//classroom discussions on 1.MAR.2012 by Mr.Dr
//IMPLEMENTATION OF MEHTOD OVERLOADING
//this program also explains the  narrowing and widening of built in data type
class math
{
int f,s;
//constructor
math()
{
f=1;
s=2;
}
//method-1
void add(double d1, double d2)
{
f=(int)d1;  //narrowing   down casting
s=(int)d2; //narrowing
int sum=f+s;
System.out.println("The sum is "+sum);
}
//METHOD-2
void add()
{
int sum=f+s;
System.out.println("The sum is "+sum);
}
//METHOD-3
void add( int d1)
{
f=d1;
s=d1;
int sum=f+s;
System.out.println("The sum is "+sum);
}
//METHOD-4
void add(int d1, int d2)
{
f=d1;
s=d2;
int sum=f+s;
System.out.println("The sum is "+sum);
}
//METHOD-5
double add(double d1, int d2)
{
f=(int)d1;
s=d2;
int sum=f+s;
System.out.println("The sum is "+sum);
return sum;    //widening up casting
}}
class polymorph
{
public static void main(String args[])
{
math m=new math();
m.add(1.1,1.2); //TWO FLOATS ADDITION
m.add(1,1);       //TWO INTEGERS ADDITION
m.add();            //NO PARAMETERS
m.add(1);          //ONE PARAMETER PASSING
double d=m.add(1.1,1); //ONE FLOAT AND ONE INTEGER
System.out.println("the sum vaule from the math class is "+d);
}}

OUTPUT:-

e:\ramu>javac polymorph.java

e:\ramu>java polymorph

The sum is 2

The sum is 2

The sum is 2

The sum is 2

The sum is 2

the sum vaule from the math class is 2.0

// three techniques for inputting from the keyboard for a java program
method-1 streams
DataInputStream d=new  DataInputStream(System.in);
//by default reading is String mode
String s=d.readLine();
//to change the data from String to integer you have to use parseInt() method
int x=Integer.parseInt(d.readLine());

mehtod-2 readers
BufferedReader br=new BufferedReader(new InputStreamReader(System.in))
//by default reading is String mode

String s=br.readLine();
//to change the data from String to integer you have to use parseInt() method
int x=Integer.parseInt(br.readLine());

 method-3 commandline mode
int x= Integer.parseInt(args[0] )
for the above technique you need to pass data at interpretation stage of a java program
java cline ramu     in this java command and cline is the .classfile ramu is the arg[0]
note all the I/O interactions throws  the IOException

constructor overloading
class box
{
//INSTANCE OR CLASS VARIABLES 
int length;
int breadth;
int height;
//method-1 constructor
box()
{
length=1;
breadth=1;
 height=1;
}

box(int l)
{
length=l;
breadth=l;
 height=l;
}
box(int l,int b)
{
length=l;
breadth=b;
 height;//no operation
}
box(int l,int b, int h)
{
length=l;
breadth=b;
 height=h;
}
write here some methods
like display()
volume()
}//end of the class

class boximpl
{ public static void main(String ramu[])
{

box b=new box();  //call for the 0 parameterized constructor

b.display();
b.volume();

box b=new box(1);  //call for the 1 parametrized constructor
b.display();
b.volume();

box b=new box(1,2);  //call for the 2 parametrized constructor b.display();
b.volume(); 

box b=new box(1,2,3);  //call for the3 parametrized constructor b.display();
b.volume(); } }

exchange data of 2 memory locations in different ways
 first way by using the temporary variable
temp=a;
a=b;
b=temp;
second way logic for with out using the temporary variable
a=a+b;
b=a-b;
a=a-b;

THIS KEYWORD  is used to refer  Present class instance variables  Present class methods. Present class constructor.

The below cited program to use ‘this’ to refer the current class parametrized constructor

and current class instance variable.

//this demo

class Person

{ String name;

Person ( )

{ this (“Ramu D”); // calling present class parametrized constructor

this.display ( ); // calling present class method

}

Person (String name)

{ this.name = name; // assigning present class variable with parameter “name”}

void display( )

{ System.out.println ("Person Name is = " + name);

}}

class ThisDemo

{ public static void main(String args[])

{Person p = new Person ( );}}