import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String s = "\\x12\\x13\\x14\\x00\\xff\\xff";
 
		// Extract valid blocks
		Pattern pattern = Pattern.compile("\\\\x[0-9A-Fa-f]{2}");
		Matcher matcher = pattern.matcher(s);
		List<String> res = new ArrayList<>();
		while (matcher.find()){
			res.add(matcher.group(0)); 
		} 
		System.out.println(res);
 
		// Check if a string consists of valid "blocks" only
		boolean isValid = s.matches("(?i)(?:\\\\x[a-f0-9]{2})+");
		System.out.println(isValid); 
 
		// More checks
		System.out.println("\\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x17".matches("(?i)(?:\\\\x[a-f0-9]{2})+"));
		System.out.println("\\x10\\x11\\x12\\x13\\x14\\x15\\16\\x1".matches("(?i)(?:\\\\x[a-f0-9]{2})+"));
	}
}

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