Cifrar.java

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package com.cuarentena;

/**
 *
 * @author Álvaro Ortiz Falcón y Arturo Martínez Menor
 */
public class Cifrar {

    public static String Cifra(int a, String b) {

        int posicion;
        boolean z;
        char letra[] = b.toCharArray();
        String abecedario = "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z";
        String abc[] = abecedario.split(" ");
        String palabra = "";

        for (char c : letra) {
            z = false;
            if (Character.isLowerCase(c)) {
                z = true;
            }
            if (Character.getNumericValue(c) - 10 >= 0 && Character.getNumericValue(c) - 10 < 26) {
                if (Character.getNumericValue(c) - 10 + a >= 26) {
                    posicion = Character.getNumericValue(c) - 10 + a - 26;
                } else if (Character.getNumericValue(c) - 10 + a < 0) {
                    posicion = Character.getNumericValue(c) - 10 + a + 26;
                } else {
                    posicion = Character.getNumericValue(c) - 10 + a;
                }
                if (z == true) {
                    palabra += abc[posicion].toLowerCase();
                } else {
                    palabra += abc[posicion];
                }
            } else {
                palabra += c;
            }
        }
        return palabra;
    }
}