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Implement the getPassword() method, which must return a ByteArrayOutputStream with the bytes comprising the password. Password requirements: 1) 8 characters. 2) Only numbers and uppercase and lowercase Latin letters. 3) At least one numeral, one lowercase letter, and one uppercase letter.
Imagine this situation: you're downloading a zip file from the Internet and in the middle of the download you lose your connection for a few seconds. You need to be sure that the downloaded zip file is valid. To do this, check its MD5 hash. Read about MD5 on Wikipedia. Read about MessageDigest.