Question

I’m using java.util.regex.Pattern to match passwords that meet the following criteria:

1. At least 7 characters
2. Must consist of only letters and digits
3. At least one letter and at least one digit

I have 1 & 2 covered, but I can’t think of how to do 3.

1 & 2 – [\\w]{7,}

Any ideas?

Answer 1

You can use this. This basically uses lookahead for achieving the 3rd requirement.

(?=.*\d)(?=.*[a-zA-Z])\w{7,}

or the Java string

"(?=.*\\d)(?=.*[a-zA-Z])\\w{7,}"

Explanation

"(?=" +         // Assert that the regex below can be matched, starting at this position (positive lookahead)
   "." +           // Match any single character
      "*" +           // Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
   "\\d" +          // Match a single digit 0..9
")" +
"(?=" +         // Assert that the regex below can be matched, starting at this position (positive lookahead)
   "." +           // Match any single character
      "*" +           // Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
"[a-zA-Z]" +       // Match a single character present in the list below
                     // A character in the range between “a” and “z”
                     // A character in the range between “A” and “Z”
")" +
"\\w" +          // Match a single character that is a “word character” (letters, digits, and underscores)
   "{7,}"          // Between 7 and unlimited times, as many times as possible, giving back as needed (greedy)

Edit

If you want to include unicode letter support, then use this

(?=.*\d)(?=.*\pL)[\pL\d]{7,}