ZCW-SimpleCrypt0/Crypto/src/ROT13.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class ROT13  {

    Integer diff;
    ROT13(Character cs, Character cf) {
        this.diff=Math.abs((int)cs-(int)cf);

    }

    ROT13() {
        this.diff = 13;
    }


    public  String crypt(String text) throws UnsupportedOperationException {
        String str="";

        for (int i=0; i<text.length(); i++)
        {
            if(!Character.isLetter(text.charAt(i)))
            {
                str+=text.charAt(i);
            }
            else if (Character.isUpperCase(text.charAt(i)))
            {
                char ch = (char)(((int)text.charAt(i) + diff - 65) % 26 + 65);
                str+=ch;
            }
            else if(Character.isLowerCase(text.charAt(i)))
            {
                char ch = (char)(((int)text.charAt(i) + diff - 97) % 26 + 97);
                str+=ch;
            }
        }
        return str;
    }

    public String encrypt(String text) {

        return crypt(text);
    }

    public String decrypt(String text) {
        return crypt(text);
    }

    public static String rotate(String string, Character c)
    {
        Integer diff=(int)c-(int)'A';
        return string.substring(diff,string.length())+string.substring(0,diff);
    }
    public static String encrpttextfile() throws FileNotFoundException {
        File file=new File("sonnet18.txt");
        Scanner sc=new Scanner(file);
        StringBuilder br =new StringBuilder();
        while(sc.hasNext())
        {
            ROT13 rot13=new ROT13();
            String str=rot13.crypt(sc.nextLine());
            br.append(str+'\n');
        }
        System.out.println(br);
        return br.toString().trim();
    }

    public static void main(String[] args) throws FileNotFoundException {
        encrpttextfile();
    }

}