How can I create a password?

Question

I want to give maybe a million password to some users that should be like:

1. It must have at least 6 characters
2. It must have digits and also letters

Answer 1

This is also a nice one:

String password = Integer.toString((int) (Math.random() * Integer.MAX_VALUE), 36);

It however does not guarantee that the password always contains both digits and letters, but most of the aforementioned suggestions also doesn't do that.