Java - Como crear programa de encriptación sencillo?

public class ejercicio8{

	public static void main (String [] args){

		byte entrada = Byte.parseByte(args[0]);

		byte salida = ((byte)128-entrada);

		System.out.println(salida);

	}

}

class Ejercicio8 {

    public static void main (String[] palabras) {

        for (String palabra : palabras) {

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

                System.out.printf("%c", 219 - palabra.charAt(i));

            }

            System.out.print(" ");

        }

    }

}

import java.util.Scanner;

public class ejercicio8{

	public static void main (String []args){

		Scanner sc = new Scanner(System.in);

		int primer = 'a';

		int ultimo = 'l';

		System.out.print("Introduce el caracter: ");

		char letra = sc.next().charAt(0);

		System.out.print("El caracter complementario es: ");

		int resultado = ultimo-letra;

		System.out.println((char)(primer+resultado));

	}

}

public class Encripter {

    private String patronBusqueda;

    private String patronEncripta;

    public Encripter() {

        patronBusqueda = "GlxnHMbcIfñK4LeUNFO1ms2PtDvSVkWXqirYTaghjZyo";

        patronEncripta = "eahdmifsWJBrWZD5CLpvMXQuVjkXqY6AoKyNzUgÑOPRt";

    }

    public String Encriptar(String cadena)

    {

       String resultado="";

        for(int pos = 0; pos< cadena.length(); pos++){

            if(pos==0){

            resultado= encriptarCaracter(cadena.substring(pos,pos+1),cadena.length(),pos);

            }

            else{

             resultado+= encriptarCaracter(cadena.substring(pos,pos+1),cadena.length(),pos);

            }

        }

    return resultado;

    }

    //----------------------

    public String encriptarCaracter(String caracter, int variable, int indice){

        int ind;

        if(patronBusqueda.indexOf(caracter)!=-1){

            ind = (patronBusqueda.indexOf(caracter) + variable + indice) % patronBusqueda.length();

        return patronEncripta.substring(ind, ind+1);

        }

    return caracter;

    }

    //----------------------

    public String desencriptaCadena(String cadena){

        String original="";

        for(int pos = 0; pos< cadena.length(); pos++){

            if(pos==0){

                original=desencriptaCaracter(cadena.substring(pos,pos+1),cadena.length(),pos);

            }

            else{

                original+=desencriptaCaracter(cadena.substring(pos,pos+1),cadena.length(),pos);

            }

        }

        return original;

    }

    //----------------------

    public String desencriptaCaracter(String caracter, int variable, int indice){

        int ind=0;

        if(patronEncripta.indexOf(caracter) != -1){

            if((patronEncripta.indexOf(caracter) - variable - indice) > 0){

            ind = (patronEncripta.indexOf(caracter) - variable - indice) % patronEncripta.length();

            }

            else{

            ind = (patronBusqueda.length()) + ((patronEncripta.indexOf(caracter)- variable - indice) % patronEncripta.length());

            }

            ind = ind % patronEncripta.length();

        return patronBusqueda.substring(ind, ind + 1);

        }

        else

        {

        return caracter;

        }

    }

    //----------------------

}