How to check if a string only consists of certain characters?

Question

Java

I need to do 3 checks:

1. the string consists only of letters and the following characters: space and hyphen;
   
2. the string consists only of a digit and the following characters: plus, minus, opening and
   closing parentheses, space character;
   
3. the string must be validated against a valid email.
   

I've read about regular expressions, but haven't been able to figure them out yet.
How can all this be implemented?

Answer 1

It can be implemented with regular expressions.
Here you can test them: https://regex101.com/
For example: "1. the string consists only of letters and the following characters: space and hyphen"
Regular: [a-zA-Z\-\s]
Test string: sdlfkj -sdfgklj ifds
By trial and error, you will recover in 6-8 hours.