I am trying to generate MD5 sum using MessageDigest. And i am having following code. 

byte[] md5sum = digest.digest();
BigInteger bigInt = new BigInteger(1, md5sum);
output = bigInt.toString(16);

This returns not 32 character string but a 31 character string 8611c0b0832bce5a19ceee626a403a7

Expected String is 08611c0b0832bce5a19ceee626a403a7

Leading 0 is missing in the output.

I tried the other method 

byte[] md5sum = digest.digest();
output = new String(Hex.encodeHex(md5sum));

And the output is as expected.

I checked the doc and Integer.toString does the conversion according to it

The digit-to-character mapping provided by Character.forDigit is used, and a minus sign is prepended if appropriate.

and in Character.forDigit methos

The digit argument is valid if 0 <=digit < radix.

Can some one tell me how two methods are different and why leading 0 is deleted?

java tostring biginteger
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