public static void main(String[] args) {

    Scanner in = new Scanner(System.in);
    int testCases = Integer.parseInt(in.nextLine());

    while(testCases > 0){
        String pattern = in.nextLine();
          try {
            "".split(pattern);
            System.out.println("Valid");

          } catch (Exception e){
            System.out.println("Invalid");
          }
          testCases--;
    }
    in.close();
}

I love about it is that it helps sharpen both logical thinking and precision, since even a tiny syntax error can make a pattern invalid. Playingexchange ID Login

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try { Pattern.compile(pattern); System.out.println("Valid"); } catch (PatternSyntaxException exc) { System.out.println("Invalid"); }

        testCases--;
    }

    in.close();
}

}

Java 8 solution:

import java.util.Scanner; import java.util.regex.*;

public class Solution { public static void main(String[] args){ Scanner in = new Scanner(System.in); int testCases = Integer.parseInt(in.nextLine()); while(testCases>0){ String pattern = in.nextLine(); //Write your code try{ Pattern.compile(pattern); System.out.println("Valid"); } catch(PatternSyntaxException e) { System.out.println("Invalid"); } testCases--; } in.close(); } }