Question

Please help me on converting a hexstring to base64

here is the cede where I’m getting the exception

 String hexString = "bf940165bcc3bca12321a5cc4c753220129337b48ad129d880f718d147a2cd1bfa79de92239ef1bc06c2f05886b0cd5d";

private static String ConvertHexStringToBase64(String hexString) {
    System.out.println(hexString);
    if ((hexString.length()) % 2 > 0)
        throw new NumberFormatException("Input string was not in a correct format.");
     byte[] buffer = new byte[hexString.length() / 2];
        int i = 0;
        while (i < hexString.length())
        {
            buffer[i / 2] = Byte.parseByte(hexString.substring(i, 2));
            i += 2;
        }
        System.out.println("hexSring"+hexString+"afterconverttobase64"+Base64.encodeBase64String(buffer));
        return Base64.encodeBase64String(buffer);

}

I’m getting an exception here::bf940165bcc3bca12321a5cc4c753220129337b48ad129d880f718d147a2cd1bfa79de92239ef1bc06c2f05886b0cd5d
Exception in thread "main" java.lang.NumberFormatException: For input string: "bf"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:449)
at java.lang.Byte.parseByte(Byte.java:151)
at java.lang.Byte.parseByte(Byte.java:108)
at com.motorola.gst.DecryptTest3.ConvertHexStringToBase64(DecryptTest3.java:38)
at com.motorola.gst.DecryptTest3.main(DecryptTest3.java:16)


Answer 1

First of all you have to specify the specify the radix(16 in your case) in the parseByte method to avoid the numberFormat exception :

 buffer[i / 2] = Byte.parseByte(hexString.substring(i, 2),16);

However your code seems broken, take a look at the corrected one :

     if ((hexString.length()) % 2 > 0)
          throw new NumberFormatException("Input string was not in a correct format.");
       int[] buffer = new int[hexString.length() / 2];
          int i = 2;
          while (i < hexString.length())
          {
              buffer[i / 2] = Integer.parseInt(hexString.substring(i, i + 2),16);
              i += 2;
          }

Your loop was wrong and you have to parse as Integer because you have some values inside your input string that overflow the byte capability …

If you need byte you could cast the parsed int to byte in this way :

       byte[] buffer = new byte[hexString.length() / 2];
          int i = 2;
          while (i < hexString.length())
          {
              buffer[i / 2] = (byte)Integer.parseInt(hexString.substring(i, i + 2),16);
              i += 2;
          }