java program to convert letters in string capital to small and vice versa

import java.util.*;
public class Convert
{
public static void main(String args[])
{
System.out.println("Enter the String");
String s1,s2="";
char ch;
Scanner in=new Scanner(System.in);
s1=in.nextLine();
int len=s1.length();
for(int i=0;i<len;i++)
{
ch=s1.charAt(i);
if(ch>=97 && ch <=122)
{
ch-=32;
}
s2=s2+ch;

}
System.out.println("Converted string is:"+s2);
}
}

java program to show the concept of if.......... else if

import java.util.Scanner;
class Year{
  public static void main(String args[]){
     int i;
     System.out.println("Enter the Number of the year");
     Scanner in=new Scanner(System.in);
     i=in.nextInt();

     if(i==1)
       System.out.println("Month is Janurary");

     else if(i==2)
       System.out.println("Month is Feburary");

     else if(i==3)
       System.out.println("Month is March");

     else if(i==4)
       System.out.println("Month is April");

     else if(i==5)
       System.out.println("Month is May");

     else if(i==6)
       System.out.println("Month is June");

     else if(i==7)
       System.out.println("Month is July");

     else if(i==8)
       System.out.println("Month is August");

     else if(i==9)
       System.out.println("Month is September");

     else if(i==10)
       System.out.println("Month is October");

     else if(i==11)
       System.out.println("Month is November");

     else if(i==12)
       System.out.println("Month is December");

     else if(i==0||i>12)
       System.out.println("Enter valid year Number");
  }
}

java program to print Fibonacci series

class Fibonacci{
  public static void main(String args[]){
    System.out.println(" Fibonacci Series ");
    int a1, a2=0, a3=1;
    for(int i=1;i<=20;i++){
     System.out.print(" "+a3+" ");
     a1 = a2;
     a2 = a3;
     a3 = a1 + a2;
     }
  }
}

java program to print the reverse of a given number

public class Combination
{
 public static int reverseNumber(int no)
 {
  int ono=0,rev=0,rem;
  ono=no;
  while(ono!=0)
  {
    rem=ono%10;
    ono/=10;
    rev= (rev*10)+rem;
  }
  return rev;

 }
 public static void main(String[] args){
 Combination.reverseNumber(123);
 }

}

java program to build calculator

import java.util.Scanner;
public class Calculator{
  public static void main(String[] args){
     System.out.println("Enter integers x,y");
     Scanner in = new Scanner(System.in);
     int a,b;
     a = in.nextInt();
     b = in.nextInt();
     int r=0;
     System.out.println(" CALCULATOR ");
     r=a+b;
     System.out.println("a + b = "+r);

     r=a-b;
     System.out.println("a - b = "+r);

     r=a*b;
     System.out.println("a * b = "+r);

     r=a/b;
     System.out.println("a / b = "+r);
  }
}

Write a program to find the largest of 3 numbers.

import java.util.Scanner;

class LargestOfThreeNumbers
{
   public static void main(String args[])
   {
      int x, y, z;
      System.out.println("Enter three integers ");
      Scanner in = new Scanner(System.in);

      x = in.nextInt();
      y = in.nextInt();
      z = in.nextInt();

      if ( x > y && x > z )
         System.out.println("First number is largest.");
      else if ( y > x && y > z )
         System.out.println("Second number is largest.");
      else if ( z > x && z > y )
         System.out.println("Third number is largest.");
      else  
         System.out.println("Entered numbers are not distinct.");
   }
}

java program to add two numbers using different Methods

simple arithmetic using command line argument

1    

      class CommanLine

  {  public static void main(String args[]){  

     int a,b,c=0;

      a=Integer.parseInt(a[0]); 

       b=Integer.parseInt(a[1]); 

     c=a+b;

5 System.out.println("sum is"+c);  

     

7  }  

8  }  

using scanner 

import java.util.Scanner;
class Add_CMD {
  public static void main(String[] args){
   int a,b,c;
   System.out.println("Enter integers ");
   Scanner in = new Scanner(System.in);
   a = in.nextInt();
   b = in.nextInt();
   c=a+b;
   System.out.println("Sum of "  + a+ " and " + b + " is " +c);

  }
}

 using BufferedReader
import java.io.*;
class Arithmatic
{
public static void main(String args[])throws IOException
{
try
{
int a,b,c,ae,nfe;
InputStreamReader isr=new InputStreamReader(System.in);
BufferedReader br=new BufferedReader(isr);
a=Integer.parseInt(br.readLine());
b=Integer.parseInt(br.readLine());
c=a/b;
System.out.println("Result="+c);
}
/*catch(ArithmeticException ae)
{
System.out.println("eror due to"+ ae.getMessage());
}
catch(NumberFormatException nfe)
{
System.out.println("error due to"+ nfe.getMessage());
}*/
catch(Exception nfe)
{
System.out.println("error due to"+ nfe.getMessage());


}

}}