DecryptTransposition

private String decryptTransposition(String secret, String key) {
        int columns = key.length();
        int rows;

        if(secret.length() % key.length() == 0){
            rows = (secret.length()/(key.length()) + 1);
        }else{
            rows = (secret.length())/(key.length()) + 2;
        }

        char [][] a = new char [rows][columns];
        for(int k=0;k<key.length();k++){
            a[0][k] = key.charAt(k);
        }

        char[] keyArr = Arrays.copyOf(key.toCharArray(), key.length());
        Arrays.sort(keyArr);
        String decryptedMessage = "";
        int secretPoint = 0;
        for (int i = 1; i < key.length(); i++)
        {
            int columnToFill =  key.indexOf(keyArr[i]);
            for(int j = 0; j < rows; j++) {
                a[j][columnToFill] = secret.charAt(secretPoint);
                secretPoint++;
            }

            for(int i=1;i< rows;i++){
                for(int j=0;j<columns;j++){
                    decryptedMessage += a[i][j];
        }
        return decryptedMessage;
    }
}