Solution: Sensitive Data Redactor

public class ContentModerator {
    public static String smartRedact(String message, String[] bannedWords) {
        // Split message into array
        String[] words = message.split(" ");
        
        // Loop through the array
        for (int i = 0; i < words.length; i++) {
            String current = words[i];
            boolean isBanned = false;
            
            // Check if current word is in bannedWords
            for (int j = 0; j < bannedWords.length; j++) {
                if (current.equals(bannedWords[j])) {
                    isBanned = true;
                    break;
                }
            }
            
            // If banned, calculate replacement and update array
            if (isBanned) {
                StringBuilder replacement = new StringBuilder();
                int len = current.length();
                
                if (len > 2) {
                    // Rule 1: Keep first and last
                    replacement.append(current.charAt(0)); 
                    for (int k = 0; k < len - 2; k++) {
                        replacement.append("*");
                    }
                    replacement.append(current.charAt(len - 1));
                } else {
                    // Rule 2: Mask entirely
                    for (int k = 0; k < len; k++) {
                        replacement.append("*");
                    }
                }
            
            // CRITICAL STEP: Overwrite the original word in the array
                words[i] = replacement.toString();
            }
        }
            
        // Rejoin the modified array into a single string
        return String.join(" ", words);
    }
    public static void main(String[] args) {
        // Scenario 1: Security
        String msg1 = "My password is password123";
        String[] banned1 = {"password", "password123"};
        
        System.out.println("--- Security Check ---");
        System.out.println("Original: " + msg1);
        System.out.println("Redacted: " + smartRedact(msg1, banned1));
        // Expected: My p******d is p*********3
        // Scenario 2: Abusive Language
        String msg2 = "You are stupid and ugly";
        String[] banned2 = {"stupid", "ugly", "bad"};
        
        System.out.println("\n--- Moderation Check ---");
        System.out.println("Original: " + msg2);
        System.out.println("Redacted: " + smartRedact(msg2, banned2));
        // Expected: You are s****d and u**y
    }
}