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 = ""; // todo
        int indexAt = 0;
        int Atnum = 0  ;
        int datnum = 0 ;
        int dat1 = 0;
        int dat2 = 0 ;
        int emsize = email.length() ;
        for (int i = 0 ; i < email.length(); i ++)
        {
            if (email.charAt(i) == '@')
            {
                indexAt = i ;
                Atnum ++ ;

            }
            if (email.charAt(i) == ' ')
            {
                return false ;
            }
        }
        if (Atnum != 1)
        {
            return  false ;
        }
        if(indexAt == 0)
        {
            return false ;
        }
        if (indexAt == 1 && email.charAt(0) == ' ')
        {
            return false ;
        }
        if (email.charAt(0) == '.' || email.charAt(Atnum-1) == '.')
        {
            return false ;
        }
        for (int i = 0 ; i <Atnum ; i++)
        {
            if (email.charAt(i) == '.')
            {

                datnum ++ ;

            }
            if (datnum == 1)
            {
                dat1 = i;
            }
            if (datnum == 2)
            {
                dat2 = i ;
            }
        }
        if (datnum > 1)
        {
            return false ;
        }
        if(indexAt== (emsize-1))
        {
            return false ;
        }
        if (indexAt == (emsize-2) && email.charAt(emsize-1) == ' ' )
        {
            return false ;
        }
        if (email.charAt(indexAt+1) == '-' || email.charAt(emsize-1) == '-')
        {
            return false ;
        }
        for (int i = indexAt ; i <emsize ; i++)
        {
            if (email.charAt(i) == '_')
            {

                return false;

            }
        }
        if(datnum == 2)
        {
            if (email.charAt(dat1+1) == '-' || email.charAt(dat2-1) == '-')
            {
                return false ;
            }
            else {
                return true ;
            }
        }


        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(email);

        return true;
    }

    /*
        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) {
        // todo
        int StartIndex  = 0 ;
        String Final = "" ;
        boolean CheckNull = true ;
        String number = "0123456789" ;
        int StrSize = string.length() ;
        for (int i = 0 ; i < StrSize ; i ++)
        {
            char x = string.charAt(i) ;
            if(number.indexOf(x) != -1)
            {
                StartIndex = i ;
                CheckNull = false ;
                break;
            }
        }
        if (CheckNull == true)
        {
            return null ;
        }



    for (int i = StartIndex ; i <StartIndex+10 ; i ++)
    {
         Final = Final + string.charAt(i)   ;
    }
        return Final;
    }

    /*
        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) {
        // todo

        String number = "0123456789" ;
        String special = "!@#$%^&*" ;
        int FinalNumber = 0 ;

        int StrSize = string.length() ;
        for(int i = 0 ; i < StrSize ; i ++)
        {
            if(string.charAt(i)==' ') continue;



            boolean check_upper = false ;
            boolean check_lower = false ;
            boolean check_number = false ;
            boolean check_special = false ;
            boolean len = false ;
            char x  = string.charAt(i) ;
            if (x != ' ' ) {
                int j = i   ;
                while (   j < StrSize && string.charAt(j) != ' ') {
                    char y = string.charAt(j) ;
                    if (Character.isDigit(y)) {
                        check_number = true;
                    }
                    if (Character.isUpperCase(y)) {
                        check_upper = true;
                    }
                    if (Character.isLowerCase(y)) {
                        check_lower = true;
                    }
                    if (special.indexOf(y) != -1) {
                        check_special = true;
                    }

                    j ++ ;

                }
                if ((j-i)>=8)
                {
                    len = true ;
                }
                i = j-1 ;
                if (len && check_lower && check_number && check_special && check_upper)
                {
                    FinalNumber ++ ;
                }
            }


        }
        return FinalNumber;
    }

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

        note: your implementation should be case-insensitive, e.g. Aba -> is palindrome
     */
    public List<String> findPalindromes(String string) {
        List<String> list = new ArrayList<>();
        // todo

        int size = string.length() ;
        for (int i = 0 ; i < size ; i ++)
        {
            if(string.charAt(i)==' ') continue;
            String pal = "" ;
            String pal2 = "" ;
            String pal3 = "" ;
            String spe = "!?.*," ;
            int j = i   ;

            while (j < size && string.charAt(j) != ' ' ) {
                char y = string.charAt(j) ;
               if (Character.isLetter(y)) {
                   pal3 = pal3 + y;
                   pal = Character.toLowerCase(y) + pal;
                   pal2 = pal2 + Character.toLowerCase(y);
               }
                j++ ;


            }
            if (pal2.equals(pal) && pal3.length()>=3)
            {
                list.add(pal3) ;
            }
            i = j - 1 ;
        }
        return list;
    }

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