Encryption and Decryption using well known Caeser Cipher technique in java.... 

class Caeser

{

public static void main(String arg[])

{

String pt="Coding Adda by TALWINDER Mann";

int key = 9;

System.out.println(" Plain Text - "+pt);

String ct =enc(pt,key);

System.out.println(" after Encryption Cipher Text - "+ct);

String cpt= dec(ct,key);

System.out.println(" after Decryption Plain Text - "+cpt);

}

        public static String enc(String pt, int key)   // Encryption 

{

String ct="";

char c;

for(int i=0; i<pt.length(); i++)

{

c = pt.charAt(i);

int ascii= c;

if(ascii>96 && ascii<124)

{

int tt= (ascii+key-97)%26+97;

ct=ct+(char)tt;

  }

if(ascii>64 && ascii<92)

{

int tt= (ascii+key-65)%26+65;

ct=ct+(char)tt;

  }

}

return ct;

}

public static String dec(String ct, int key)  //Decryption... 

{

String pt="";

char c;

for(int i=0; i<ct.length(); i++)

{

c = ct.charAt(i);

int ascii= c;

if(ascii>96 && ascii<124)

{

int tt= ((ascii+26) - 97-key)%26+97;

pt=pt+(char)tt;

  }

if(ascii>64 && ascii<92)

{

int tt= ((ascii+26)- key-65)%26+65;

pt=pt+(char)tt;

  }

}

return pt;

}

}