Question

Write a Java program that prompts the user to enter a password that matches a specific pattern. Your program must approve the user's entry.. Here is the pattern, in this order:

• 1 or more upper case letters
• two lower case letters
• 1 or 2 digits
• zero or 1 upper case letters
• any two of this group @#$%^&

Answer 1

//PatternMatching.java

import java.util.Scanner;
import java.util.regex.*;//Java Regex or Regular Expression is an API to define a pattern for searching or manipulating strings.
public class Recursion1 {

   public static void main(String[] args) {
      
       Scanner s = new Scanner(System.in); //Scanner object to input password
       System.out.println("Enter passwrod : ");
       String password = s.next();
       Pattern pattern = Pattern.compile("[A-Z]+");   //compiling the Pattern with the regex(the pattern to be searched within password
       Matcher matcher = pattern.matcher(password);   //matcher object to find for the given pattern(/regex)
       if(matcher.find())               //returns true if the given pattern exists within the string (password)
       {
           System.out.println("Password Approved");
       }
      
       pattern = Pattern.compile("[a-z]{2}");   //compiling the Pattern with the regex(the pattern to be searched within password
       matcher = pattern.matcher(password);   //matcher object to find for the given pattern(/regex)
       if(matcher.find())               //returns true if the given pattern exists within the string (password)
       {
           System.out.println("Password Approved");
       }
       pattern = Pattern.compile("[0-9]{1,2}");   //compiling the Pattern with the regex(the pattern to be searched within password
       matcher = pattern.matcher(password);   //matcher object to find for the given pattern(/regex)
       if(matcher.find())               //returns true if the given pattern exists within the string (password)
       {
           System.out.println("Password Approved");
       }
       pattern = Pattern.compile("[0-9]{1,2}");   //compiling the Pattern with the regex(the pattern to be searched within password
       matcher = pattern.matcher(password);   //matcher object to find for the given pattern(/regex)
       if(matcher.find())               //returns true if the given pattern exists within the string (password)
       {
           System.out.println("Password Approved");
       }
       pattern = Pattern.compile("[A-Z]?");   //compiling the Pattern with the regex(the pattern to be searched within password
       matcher = pattern.matcher(password);   //matcher object to find for the given pattern(/regex)
       if(matcher.find())               //returns true if the given pattern exists within the string (password)
       {
           System.out.println("Password Approved");
       }
       pattern = Pattern.compile("[@#$%^&]{2}");   //compiling the Pattern with the regex(the pattern to be searched within password
       matcher = pattern.matcher(password);   //matcher object to find for the given pattern(/regex)
       if(matcher.find())               //returns true if the given pattern exists within the string (password)
       {
           System.out.println("Password Approved");
       }
       pattern = Pattern.compile("[A-Z]+[a-z]{2}[\\\\d]{1,2}[A-Z]{0,1}[@#$%^&]{2}");   //compiling the Pattern with the regex(the pattern to be searched within password
       matcher = pattern.matcher(password);   //matcher object to find for the given pattern(/regex)
       if(matcher.find())               //returns true if the given pattern exists within the string (password)
       {
           System.out.println("Password Approved");
       }
      
//       System.out.println(Pattern.matches("[A-Z]+",password)); //1 or more uppercase letters
//       System.out.println(Pattern.matches("[a-z]{2}", password)); //two lower case letters
//       System.out.println(Pattern.matches("[\\d]{1,2}",password));//1 or 2 digits
//       System.out.println(Pattern.matches("[A-Z]?",password));//zero or 1 upper case letters
//       System.out.println(Pattern.matches("[@#$%^&]{2}", password));//any two of this group @#$%^&
//       System.out.println(Pattern.matches("[A-Z]+[a-z]{2}[\\d]{1,2}[A-Z]{0,1}[@#$%^&]{2}",password));
      
       if(password.matches("[A-Z]+[a-z]{2}[\\d]{1,2}[A-Z]{0,1}[@#$%^&]{2}"))
       {
           //if the password matches all of the above patterns in the same order as given
           System.out.println("Password Approved");
       }
       /*
       * It is not clearly understood if the question asks to approve the password only when all of the above pattern matches in the
       * exact same order as given. If so the answer is in the above if{} condition. Rest individual conditions check have been
       * applied has well so as to understand how pattern matching is working. You can combine the results to achieve desired results.
       */
   }
}