extra_examples

import java.util.Scanner;
public class String_Practice_Examples {
// extra examples on Java string and array 2D
    public static void main(String[] args) {
        // TODO: check if an email is valid or not
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.print("Enter an email (or type 'exit' to quit): ");
            String email = scanner.nextLine();
            if (email.equalsIgnoreCase("exit")) {
                System.out.println("Goodbye!");
                break;
            }
            try {
                 checkEmail(email); // Validate
                String masked = maskEmail(email);
                System.out.println("Original: " + email);
                System.out.println("Masked:   " + masked);
            } catch (IllegalArgumentException e) {
                System.out.println("Error: " + e.getMessage());
            }
        }
        scanner.close();

        // TODO: word and letter counter
        String text = "Java is powerful! 123";
        int wordCount = countWords(text);
        int letterCount = countLetters(text);
        System.out.println("Total words: " + wordCount);
        System.out.println("Total letters: " + letterCount);

        // TODO: search word in 2d array rows or columns
        char[][] grid = {
                {'J', 'A', 'V', 'A'},
                {'P', 'Y', 'T', 'H'},
                {'C', 'P', 'H', 'P'},
                {'R', 'U', 'B', 'Y'}
        };
        String word = "JAVA";
        boolean found = findWordInGrid(grid, word);
        if (!found) {
            System.out.println("Word \"" + word + "\" not found in grid.");
        }

    }// end of main method

    // TODO: check email validity mask the email method
    public static void checkEmail(String email) {
        if (email == null || email.trim().isEmpty()) {
            throw new IllegalArgumentException("Email cannot be empty.");
        }
        email = email.trim();
        if (!email.contains("@") || !email.contains(".") ||
                email.indexOf("@") > email.lastIndexOf(".") ||
                email.startsWith("@") || email.endsWith(".") ||
                email.length() < 5) {
            throw new IllegalArgumentException("Invalid email format.");
        }
    }
    public static String maskEmail(String email) {
        email = email.trim();
        int atIndex = email.indexOf('@');
        if (atIndex <= 1) {
            return "***" + email.substring(atIndex);
        }
        char first = email.charAt(0);
        char last = email.charAt(atIndex - 1);
        String domain = email.substring(atIndex);
        return first + "***" + last + domain;
    }

    // TODO: word and letter counter methods
    public static int countWords(String text) {
        int count = 0;
        boolean lastWasSpace = true;
        for (int i = 0; i < text.length(); i++) {
            char ch = text.charAt(i);
            if (Character.isLetterOrDigit(ch)) {
                if (lastWasSpace) {
                    count++;
                    lastWasSpace = false;
                }
            }
            else {
                lastWasSpace = true;
            }
        }
        return count;
    }
    public static int countLetters(String text) {
        int count = 0;
        for (int i = 0; i < text.length(); i++) {
            char ch = text.charAt(i);
            if (Character.isLetter(ch)) {
                count++;
            }
        }
        return count;
    }

    // TODO: search 2d array for a word method
    public static boolean findWordInGrid(char[][] grid, String word) {
        int rows = grid.length;
        int cols = grid[0].length;
        // Check each row
        for (int i = 0; i < rows; i++) {
            String row = "";
            for (int j = 0; j < cols; j++) {
                row += grid[i][j];
            }
            if (row.contains(word)) {
                System.out.println("Word \"" + word + "\" found in row " + i);
                return true;
            }
        }
        // Check each column
        for (int j = 0; j < cols; j++) {
            String col = "";
            for (int i = 0; i < rows; i++) {
                col += grid[i][j];
            }
            if (col.contains(word)) {
                System.out.println("Word \"" + word + "\" found in column " + j);
                return true;
            }
        }
        return false;
    }
}