Sandeep Kumar: Java

Sample Programs :

· Can we overload main() method·
· Can we override main method in java
·                  Program to Date into String Type and Date Type.
·                  Area

· Program to calculate Biggest no from given 3 no's

· Prime Number

· Program to Determine Palindrome
· Program to Calculate Pi value upto 50 decimal places.

Can we overload main() method in java:
Yes we can !!

But only public static void main(String[] args) will be used when your class is launched by JVM , as :-

But it will always print main(String[] args)

public class Test {
public static void main(String[] args) {
System.out.println("main(String[] args)");
}

public static void main(String arg1) {
System.out.println("main(String arg1)");
}

public static void main(String arg1, String arg2) {
System.out.println("main(String arg1, String arg2)");
}
}

We can call the main() method yourself from code, of course - at which point the normal overloading rules will be applied.
Note that you can use a varargs signature, as that's equivalent from a JVM standpoint: -
public static void main(String... args)

Can we override the main method in java

No!
main is a static method, and is thus not polymorphic. You may hide it be defining another static main method in a subclass, though.

Java Program to Convert Date Type to String and vice versa:

import java.text.SimpleDateFormat;
import java.util.Locale;

public class Date
{
    public static void main(String[] args) throws ParseException
    {
        String string = "12-02-2012";
        /* Converting from String to Date type */
        java.util.Date date1 = new SimpleDateFormat("dd-MM-yyyy",Locale.ENGLISH).parse(string);
        System.out.println("DateType-date-is ----->"+date1);

        /* Converting from DateType Date to String type */
        DateFormat formater = new SimpleDateFormat("dd-MM-yyyy");
        String date2 = formater.format(date1);
        System.out.println("StringType-date-is --->"+date2);


    }
}

/*
output:-
DateType-date-is ----->Sun Feb 12 00:00:00 IST 2012
StringType-date-is --->12-02-2012
*/

Java Program to calculate Area and perimeter of a square:

import java.util.Scanner;
public class Area
{
static int a,l,b,p;
public static void main(String[] args)
{
System.out.println("Programe to calculate Area and Perimeter of Square or Rctangle ");
Scanner l=new Scanner(System.in);
System.out.println("Enter length:");
String s1=l.next();
int i=Integer.parseInt(s1);
Scanner b=new Scanner(System.in);
System.out.println("Enter Breadth: ");
String s2=b.next();
int j=Integer.parseInt(s2);
a=i*j;
p=2*(i+j);
System.out.println("Area of the given square/rectange is: "+a);
System.out.println("Perimeter of the square/rectangle is: "+p);
}
}

output:

Programe to calculate Area and Perimeter of Square or Rctangle

Enter length:

Enter Breadth:

Area of the given square/rectange is: 30

Perimeter of the square/rectangle is: 22

*/

Program to calculate Biggest no from given 3 no's
import java.util.Scanner;
public class Big
{
int a,b,c,i,j,k;
Big(int i,int j,int k)
{
if((i>j) && (i>k))
{
   System.out.println("The biggest No is: "+i);
}
else if(j>k)
{
   System.out.println("The biggest No is: "+j);
}
else
{
   System.out.println("The biggest No is: "+k);
}
}

public static void main(String[] args)
{
System.out.println("Program to calculate Biggest no from given 3 no's");
Scanner a=new Scanner(System.in);
System.out.println("Enter First Number:");
String s1=a.next();
int i=Integer.parseInt(s1);
Scanner b=new Scanner(System.in);
System.out.println("Enter Second Number:");
String s2=b.next();
int j=Integer.parseInt(s2);
Scanner c=new Scanner(System.in);
System.out.println("Enter Third Number:");
String s3=b.next();
int k=Integer.parseInt(s3);
Big obj=new Big(i,j,k);

}
}

/*
output:

Program to calculate Biggest no from given 3 no's
Enter First Number:
5
Enter Second Number:
9
Enter Third Number:
-8
The biggest No is: 9

Prime Number

import java.util.Scanner;
public class Prime
{
Prime(int j)
{
int i=1;
int k=1;
i++;
while(i<=j)
{
   if(j%i==0)
   {
    k=k+1;
   }
   i++;
}
if(k==2)
{
   System.out.println(j+" Is a prime number ");
}
else
{
   System.out.println(j+" Is not a prime number");
}
}
public static void main(String[] args)
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter any Number to find whether it is prime or not: ");
String s1=sc.next();
int n=Integer.parseInt(s1);
Prime obj=new Prime(n);
}
}

/*
output:

Enter any Number to find whether it is prime or not:
3
3 Is a prime number

*/

Program to Determine Palindrome

package com.san;
import java.util.Scanner;

public class Palindrome
{
static int l;
public static void main(String[] args)
{
System.out.println("Programe to Determine Palindrome ");
Scanner p=new Scanner(System.in);
System.out.println("Enter a String:");
String s1=p.next();
String s2=new StringBuffer(s1).reverse().toString();
if(s1.equals(s2))
{
   System.out.println("String is Palindrome");
}
else
{
   System.out.println("String is not a Palindrome");
}
}
}

output:-

Programe to Determine Palindrome

Enter a String:

i am a i

String is Palindrome

*/

Java Program to calculate Pi value upto 50 decimal places:

import java.math.BigDecimal;

public class PiReCalc {
    public static final int N = 1000; // # of terms
       public static void main(String[] args) {
    BigDecimal sum = new BigDecimal(0);      // final sum
    BigDecimal term = new BigDecimal(0);           // term without sign
    BigDecimal sign = new BigDecimal(1.0);     // sign on each term

    BigDecimal one = new BigDecimal(1.0);
    BigDecimal two = new BigDecimal(2.0);

    for (int k = 0; k < N; k++) {
         BigDecimal count = new BigDecimal(k);
         //term = 1.0/(2.0*k + 1.0);
         BigDecimal temp1 = two.multiply(count);
         BigDecimal temp2 = temp1.add(one);

         // The divide takes three arguments ie. BigDecimal divisor, int scale, int roundingMode
        // We provided scale as 50 for getting 50 decimal points
         term = one.divide(temp2,50,BigDecimal.ROUND_FLOOR);

         //sum = sum + sign*term;
         BigDecimal temp3 = sign.multiply(term);
         sum = sum.add(temp3);

         sign = sign.negate();
    }
    BigDecimal pi = new BigDecimal(0);
    BigDecimal four = new BigDecimal(4);
    pi = sum.multiply(four);

    System.out.println("Calculated pi (approx., " + N + " terms and 50 Decimal Places): " + pi);
    System.out.println("Actual pi: " + Math.PI);
       }
}

output:-

Calculated pi (approx., 1000 terms and 50 Decimal Places): 3.14059265383979292596359650286939597045138933077984
Actual pi: 3.141592653589793*/