Using regex for switch-statement in Java

Question

void menu() {     print();     Scanner input = new Scanner( System.in );     while(true) {         String s = input.next();         switch (s) {         case "m": print(); continue;         case "s": stat(); break;         case "[A-Z]{1}[a-z]{2}\\d{1,}": filminfo( s ); break;         case "Jur1": filminfo(s); break; //For debugging - this worked fine         case "q": ; return;         }     } } 

It seems like either my regex is off or that I am not using it right in the case-statement. What I want is a string that: Begins with exactly one uppercase letter and is followed by exactly two lowercase letters, which are followed by at least one digit.

I've checked out the regex API and tried the three variants (greedy, reluctant and possessive quantifiers) without knowing their proper use. Also checked the methods for String without finding a method that seemed pertinent to my needs.

Answer 1

You can't use a regex as a switch case. (Think about it: how would Java know whether you wanted to match the string "[A-Z]{1}[a-z]{2}\\d{1,}" or the regex?)

What you could do, in this case, is try to match the regex in your default case.

    switch (s) {         case "m": print(); continue;         case "s": stat(); break;         case "q": return;         default:             if (s.matches("[A-Z]{1}[a-z]{2}\\d{1,}")) {                 filminfo( s );             }             break;     } 

(BTW, this will only work with Java 7 and later. There's no switching on strings prior to that.)