Base 62 String Decode

gistfile1.java

byte[] strValDecode(String s)
{
    final String alphabet = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  
    BigInteger b = BigInteger.ZERO;
    BigInteger b62 = new BigInteger("62");

    for (int i=0; i<s.length(); i++) {
        int idx = alphabet.indexOf(s.codePointAt(i));
        b = b.multiply(b62).add(new BigInteger(Integer.toString(idx)));
    }
  
    return b.toByteArray();
}