Encryption/Decryption

//Strange issue with this is I for some reason can't use any characters in an Encryption code that are going to get //Encrypted be the next Encryption...?!

import java.io.*;
import java.util.*;

/**
 * Write a description of class CryptoTest here.
 *
 * @author (your name)
 * @version (a version number or a date)
 */
public class CryptoTest
{
    public static void main(String args[])
    {
        //Scanner kbReader = new Scanner(System.in);
        System.out.print("Enter a sentence that is to be encrypted: ");
        String sntnc = "This is a very big morning.";//kbReader.nextLine( );
        System.out.println("Original sentence = " + sntnc);
        MyCrypto myCryptObj = new MyCrypto( );
        String encryptdSntnc = myCryptObj.encrypt2(sntnc);
        System.out.println("Encrypted sentence = " + encryptdSntnc);
        String decryptdSntnc = myCryptObj.decrypt2(encryptdSntnc);
        System.out.println("Decrypted sentence = " + decryptdSntnc);
    }

    /*
     * Enter a sentence that is to be encrypted: This is a very big morning.
     * Original sentence = This is a very big morning.
     * Encrypted sentence = This is a ag',rery dug>?/ijeb..w ssadorninjeb..w.
     * V = ag',r
     * B = dug>?/
     * G = jeb..w
     * M = ssad
     *
     * Decrypted sentence = This is a very big morning.
     *
     *
     */

}



import java.io.*;
import java.util.*;
/**
 * Write a description of class MyCrypto here.
 *
 * @author (your name)
 * @version (a version number or a date)
 */
public class MyCrypto
{
    public String MN;
    public String Hold1;
    public String Hold2;
    private String Ch1;
    private String Ch2;
    private String Ch3;
    private String[] Tar = new String[4];
    private String[] Rep = new String[4];
    /**
     * Constructor for objects of class MyCrypto
     */
    public MyCrypto()
    {
        //
        Ch1 = "agfgr";
        Ch2 = "jeb..w";
        Ch3 = "ssad";

        Tar[0] = "v";
        Tar[1] = "g";
        Tar[2] = "m";
        Tar[3] = "b";

        Rep[0] = "g";
        Rep[1] = "v";
        Rep[2] = "b";
        Rep[3] = "m";
    }

    public String encrypt(String E)
    {
        MN = E.replace("v", Ch1);
        Hold1 = MN.replace("g", Ch2);
        MN = Hold1;
        Hold2 = MN.replace("m", Ch3);
        MN = Hold2;

        return MN;
    }
    public String decrypt(String D)
    {
        MN = D;
        Hold1 = MN.replace(Ch2, "g");
        MN = Hold1;
        Hold2 = MN.replace(Ch3, "m");
        MN = Hold2;
        String Test = MN.replace(Ch1, "v");
        MN = Test;
        return MN;
    }

    public String encrypt2(String E)
    {
        MN = E;
        int Run = 0;
        while(Run < 4)
        {
            Hold1 = MN.replace(Tar[Run], Rep[Run]);
            MN = Hold1;
            Run++;
        }

        return MN;
    }
    public String decrypt2(String E)
    {
        MN = E;
        int Run = 0;
        while(Run < 4)
        {
            Hold1 = MN.replace(Rep[Run], Tar[Run]);
            MN = Hold1;
            Run++;
        }

        return MN;
    }
}