I don\'t want to calculate a file\'s checksum, just to know if a given string is a valid checksum
SHA1 verifier:
public boolean isValidSHA1(String s) { return s.matches("^[a-fA-F0-9]{40}$"); }
MD5 verifier:
public boolean isValidMD5(String s) { return s.matches("^[a-fA-F0-9]{32}$"); }