Dear Ben,
I strongly agree with Jhon. Java uses, python based regular expressions for your information.
On the other hand, you can pick up some sample problems from your daily life. For example, how to create a regex for an email, how to create a regex for
a credit card or a telephone number. Regular expressions cannot be learnt in one day. It's a very strong language itself and it takes time to gain mastery in it.
Most important thing is, you can keep practising. For further reference, i would strongly suggest you to read
Mastering Regular Expressions.
HTH,