PatternSyntaxChecker.java

//Using Regex, we can easily match or search for patterns in a text. Before searching for a pattern, we have to specify one using some well-defined syntax.

//In this problem, you are given a pattern. You have to check whether the syntax of the given pattern is valid.

//Note: In this problem, a regex is only valid if you can compile it using the Pattern.compile method.

//Input Format
//The first line of input contains an integer N, denoting the number of test cases. The next  lines contain a string of any printable characters representing the pattern of a regex.

//Output Format
//For each test case, print Valid if the syntax of the given pattern is correct. Otherwise, print Invalid. Do not print the quotes.

//Sample Input:
//3
//([A-Z])(.+)
//[AZ[a-z](a-z)
//batcatpat(nat

//Sample Output:
//Valid
//Invalid
//Invalid

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) && (in.hasNextLine())){
			String pattern = in.nextLine();

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