NS-Lab/SystemLog/CaesarCipher.java

import java.io.*;
public class CaesarCipher {
	
	static String encrypt(String PlainText,int Key)
	{
		String cipherText="";
		int index=0,offset=0,charAscii=0,CharVal=0;
		//char ctext[]=new char[PlainText.length()] ;
		//PlainText.toLowerCase();
		//ctext=cipherText.toCharArray();
		System.out.println("PlainText Length: "+PlainText.length());
		for(index=0;index<PlainText.length();index++)
		{
			if(PlainText.charAt(index)==' '){
				cipherText+=' ';
				continue;
			}
			charAscii=PlainText.charAt(index)+Key;
			CharVal=PlainText.charAt(index);
			if((charAscii-48)>=10 && CharVal>=48 && CharVal<=57)// && charAscii<=58 )
			{
				offset=(charAscii-48)%10;
				cipherText+=(char)(offset+48);
			}
			else if((charAscii-97) >= 26 && CharVal>=97 && CharVal<=122)
			{
				offset=(charAscii-97)%26;
				cipherText+=(char)(offset+97);
			}
			else if((charAscii-65) >= 26 && CharVal>=65 && CharVal<=90)
			{
				offset=(charAscii-65)%26;
				cipherText+=(char)(offset+65);
			}
			else
			{
			//ctext[index]=(char) (PlainText.charAt(index)+3);
			//System.out.println((char) (PlainText.charAt(index)+3));
			cipherText+=((char) (PlainText.charAt(index)+Key));
			//System.out.println(cipherText);
			}	
		}
		System.out.println("CipherText is: "+cipherText);
		return cipherText;
	}
	static String decrypt(String cipherText,int Key)
	{
		String PlainText="";
		int index=0,offset=0,charAscii=0,CharVal=0;
		//char ctext[]=new char[PlainText.length()] ;
		//PlainText.toLowerCase();
		//ctext=cipherText.toCharArray();
		System.out.println("CipherText Length: "+cipherText.length());
		for(index=0;index<cipherText.length();index++)
		{
			if(cipherText.charAt(index)==' '){
				PlainText+=' ';
				continue;
			}
			charAscii=cipherText.charAt(index)-Key;
			CharVal=cipherText.charAt(index);
			if((charAscii)<48 && CharVal>=48 && CharVal<=57)//&& charAscii>=38)
			{
				offset=(charAscii-48)%10;
				if(offset<0)
					offset=-(offset);
				if(offset==0)
					PlainText+='0';
				else
				PlainText+=(char)(57-offset+1);
			}
			else if(charAscii<65 && CharVal>=65 && CharVal<=90)
			{
				offset=(charAscii-65)%26;
				if(offset<0)
					offset=-(offset);
				if(offset==0)
					PlainText+='A';
				else
				PlainText+=(char)(90-offset+1);
			}
			else if((charAscii)<97 && CharVal>=97 && CharVal<=122)// && charAscii>90)
			{
				offset=(charAscii-97)%26;
				if(offset<0)
					offset=-(offset);
				if(offset==0)
					PlainText+='a';
				else
					PlainText+=(char)(122-offset+1);
			}
			
			else
			{
			//ctext[index]=(char) (PlainText.charAt(index)+3);
			//System.out.println((char) (PlainText.charAt(index)+3));
			PlainText+=((char) (cipherText.charAt(index)-Key));
			//System.out.println(cipherText);
			}	
		}
		System.out.println("PlainText is: "+PlainText);
		return cipherText;
	}
	public static void main(String args[])
	{
		String ptext=null,cipherText=null;
		int Key=0;
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		
		try {
			System.out.println("Enter the PlainText");
			ptext=br.readLine();
			System.out.println("Enter the Key");
			Key=Integer.parseInt(br.readLine());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			System.out.println("Exception:"+e.getCause());
		}
		cipherText=encrypt(ptext,Key);
		decrypt(cipherText,Key);
	}
}