Recreating MD5 - How To Work With Bits?

What would be the most efficient way to work with bits? Example; how would I implement 3.1 in accordance with http://tools.ietf.org/html/rfc1321 ?
[160 byte] By [Kane635a] at [2007-10-3 2:45:04]
# 1
why? md5 ist not very good. and what aboutjava.security.MessageDigest.getInstance("MD5")?
Maaartina at 2007-7-14 20:33:39 > top of Java-index,Security,Cryptography...