Drehraster Verschlüsselung - Matrix

/**
 * Beschreiben Sie hier die Klasse main.
 *
 * @author (Ihr Name)
 * @version (eine Versionsnummer oder ein Datum)
 */
public class matrixRaster
{
    public static void main(String[] args)
    {
        System.out.println("Encrypted: " + encrypt("ICHBINDERDOKTOREISENBART",6));
        System.out.println("--------------------------------------------------");
        System.out.println("Decrypted: " + decrypt("IDTECEONHRRBBDEAIOIRNKST   ", 6));
    }

    private static String encrypt(String pText, int encryptionKey)
    {
        //Initialize String Builder to build encrypted String
        StringBuilder sb = new StringBuilder();
        //calculate rows based on encryptionKey (+1 if text length is not divisible by encryptionKey)
        int zeile = (pText.length()%encryptionKey == 0 ? pText.length()/encryptionKey : pText.length()/encryptionKey+1),
        spalte = encryptionKey;
        //Create matrix according to columns and rows
        char[][] matrix = new char[zeile][spalte];
        //fill matrix
        for(int i = 0; i < zeile; i++)
        {
            for(int j = 0; j < spalte; j++)
            {
                //fill first letter of string into matrix
                matrix[i][j] = pText.charAt(0);
                //can't fill the matrix with no characters left.
                if(pText.length() <= 1)break;
                //remove first letter of string
                pText = pText.substring(1);
            }
        }
        //print matrix
        System.out.println("Matrix: ");
        printMatrix(matrix);
        //read matrix from top to bottom to build encrypted string
        for(int i = 0; i < spalte; i++)
        {
            for(int j = 0; j < zeile; j++)
            {
                sb.append(matrix[j][i]);
            }
        }
        System.out.println();
        //return encrypted String
        return sb.toString();
    }

    private static String decrypt(String pText, int decryptionKey)
    {
        //when swapping columns with rows while encrypting an already encrypted string, it actually decrypts said string
        return encrypt(pText,(pText.length()/decryptionKey));
    }

    private static void printMatrix(char[][] matrix)
    {
        for(int i = 0; i < matrix.length; i++)
        {
            for(int j = 0; j < matrix[i].length; j++)
                System.out.print(matrix[i][j]);
            System.out.println();
        }
    }
}