HW-02-git-and-java-practice/src/main/java/BonusExercises.java

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class BonusExercises {

    /*
        complete the method below, so it will validate an email address
        1. Must have exactly one @ (no more, no less)
        2. Split into local-part and domain (before @ and after @)
        3. Local-part rules:
            - Can't be empty
            - Can't start or end with dot
            - Can't have two dots in a row
        4. Domain rules:
            - Can't be empty
            - Can't start or end with hyphen
            - Can't have underscores
            - Each segment (between dots) must follow same hyphen rules
     */
    public boolean validateEmail(String email) {
        String regex = "^(?!.*\\.\\.)[a-zA-Z0-9]([a-zA-Z0-9_.-]*[a-zA-Z0-9])?@[a-zA-Z0-9]([a-zA-Z0-9-]*[a-zA-Z0-9])?(\\.[a-zA-Z0-9]([a-zA-Z0-9-]*[a-zA-Z0-9])?)*$";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(email);

        return matcher.matches();
    }

    /*
        This method should find and return the first date in a string.

        Supported formats:
        - American:   MM/DD/YYYY   (e.g., 12/09/2023)
        - British:    DD/MM/YYYY   (e.g., 12/09/2023 — same pattern, context matters)
        - ISO:        YYYY-MM-DD   (e.g., 2024-07-15)
        - Slash variant: YYYY/MM/DD (e.g., 2025/01/01)

        If no match for a date is found in the string, return null.
    */
    public String findDate(String string) {
//        String regex = "\\b(\\d{4}[/-]\\d{2}[/-]\\d{2}|\\d{2}[/-]\\d{2}[/-]\\d{4})\\b";
//        Pattern pattern = Pattern.compile(regex);
//        Matcher matcher = pattern.matcher(string);
//        if (matcher.find())
//        {
//            return matcher.group();
//        }
        //Checking day-month compatibility!!!!!!
        return null;
    }

    /*
        given a string, implement the method to detect all valid passwords
        then, it should return the count of them

        a valid password has the following properties:
        - at least 8 characters
        - has to include at least one uppercase letter, and at least a lowercase
        - at least one number and at least a special char "!@#$%^&*"
        - has no white-space in it
     */
    public int findValidPasswords(String string) {
        if (string == null) {return 0;}
        String[] words = string.split("\\s+");
        int passwordCount = 0;
        for (String word : words)
        {
            String cleanWord = cleanWord(word);
            if (isValid(cleanWord))
            {
                passwordCount++;
            }
        }
        return passwordCount;
    }

    private String cleanWord(String word) {
        return word.replaceAll("[^a-zA-Z0-9!@#$%^&*]", "");
    }

    private boolean isValid(String word)
    {
        if (word.length() < 8)
        {
            return false;
        }

        boolean hasUppercase = false;
        boolean hasLowercase = false;
        boolean hasSpecial = false;
        boolean hasNumber = false;
        String special = "!@#$%^&*";

        for (int i = 0; i < word.length(); i++)
        {
            char c = word.charAt(i);
            if (Character.isUpperCase(c))
            {
                hasUppercase = true;
            }
            else if (Character.isLowerCase(c))
            {
                hasLowercase = true;
            }
            else if (Character.isDigit(c))
            {
                hasNumber = true;
            }
            else if (special.indexOf(c) != -1)
            {
                hasSpecial = true;
            }
            else
            {
                return false;
            }
        }
        return hasNumber && hasLowercase && hasSpecial && hasUppercase;
    }

    /*
        you should return a list of *words* which are palindromic
        by word we mean at least 3 letters with no whitespace in it

        note: your implementation should be case-insensitive, e.g. Aba -> is palindrome
     */
    public List<String> findPalindromes(String string) {
        List<String> list = new ArrayList<>();
        Pattern pattern = Pattern.compile("[a-zA-Z]+");
        Matcher matcher = pattern.matcher(string);
        while (matcher.find())
        {
            String word = matcher.group();
            if (word.length() >= 3) {
                String lowerWord = word.toLowerCase();
                if (isPalindrome(lowerWord)) {
                    list.add(word);
                }
            }
        }
        return list;
    }

    private boolean isPalindrome(String word)
    {
        boolean isPalindrome = true;
        int length = word.length();
        for (int i = 0; i < length/2; i++)
        {
            if (word.charAt(i) != word.charAt(length - i - 1))
            {
                isPalindrome = false;
            }
        }
        return isPalindrome;
    }

    public static void main(String[] args) {
        // you can test your code here
    }
}