This works:

String rex = "^\\d+\\.\\s\\p{Lu}+.*";

System.out.println("1. PTYU fmmflksfkslfsm".matches(rex));
// true

System.out.println(". PTYU fmmflksfkslfsm".matches(rex));
// false, missing leading digit

System.out.println("1.PTYU fmmflksfkslfsm".matches(rex));
// false, missing space after .

System.out.println("1. xPTYU fmmflksfkslfsm".matches(rex));
// false, lower case letter before the upper case letters

Breaking it down:

• ^ = Start of string
• \d+ = One or more digits (the \ is escaped because it's in a string, hence \\)
• \. = A literal . (or your original [.] is fine) (again, escaped in the string)
• \s = One whitespace char (no need for the {1} after it) (I'll stop mentioning the escapes now)
• \p{Lu}+ = One or more upper case letters (using the proper Unicode escape — thank you, tchrist, for pointing this out in your comment below. In English terms, the equivalent would be [A-Z]+)
• .* = Anything else

See the documentation here for details.

You only need the .* at the end if you're using a method like String#match (above) that will try to match the entire string.