I have the following switch statement.

    switch (grade) {
        case "a":
        case "b":
        case "c":
        case "d":
        case "a ":
        case "b ":
        case "c ":
        case "d ":
        case "a-":
        case "b-":
        case "c-":
        case "d-":
        case "e":
        case "f":
        case "i":
        case "w":
        case "z": {
            return true;
        }
                                
       
    }
    return false;

I wanted to convert it to a regex statement. I was thinking of doing something similar, but is there a better way to allow a, A, b, B and b , B , a-, A- and etc?

The cases would be upper and lower, and only A-D will allow /-... everything else will fail.

CodePudding user response：

A pattern for those values, using a case insensitive match might be:

(?i)^(?:[a-d][ -]?|[efiwz])$

In parts, the pattern matches:

• (?i) Inline modifier for a case insensitive match
• ^ Start of string
• (?: Non capture group for the alternation |
  • [a-d][ -]? Match a range a-d chars and optional or -
  • | Or
  • [efiwz] Matc any of the single listed chars
• ) Close non capture group
• $ End of string

See a regex demo.

For example:

System.out.println("A".matches("(?i)^(?:[a-d][ -]?|[efiwz])$"));
System.out.println("x".matches("(?i)^(?:[a-d][ -]?|[efiwz])$"));

Output

true
false

For only the chars a-d in lower and uppercase:

(?i)^[a-d][ -]?$

Regex demo

CodePudding user response：

According to the description in the question:

The cases would be upper and lower, and only A-D will allow /-... everything else will fail.

A possibile pattern is

(([A-D]|[a-d])[ -]?)

If the correct scenario is instead what is written in your switch statement, then The fourth bird's answer is indeed correct.