Added JavaDoc commenting to several classes.

src/main/java/com/chatbot/connectors/DatabaseConnector.java

-package com.chatbot;
+package com.chatbot.connectors;
+
+import com.chatbot.managers.QAManager;
+import com.chatbot.models.Password;
+import com.chatbot.models.QA;
+import com.chatbot.models.Secrets;
+
 import javax.sql.rowset.serial.SerialBlob;
 import java.sql.*;
 import java.util.ArrayList;
 
+
+/**
+ * A singleton class for connecting to the database and performing CRUD operations.
+ */
 public class DatabaseConnector {
     private static DatabaseConnector db_instance = null;
     private final String host, username, password;
@@ -10,92 +20,139 @@ public class DatabaseConnector {
     private Statement statement;
     private ArrayList<QA> qas;
     private boolean canConnect = false;
-    public DatabaseConnector(){
+
+    /**
+     * constructor for initializing database connection properties.
+     */
+    public DatabaseConnector() {
         host = System.getenv("host");
         username = System.getenv("username");
         password = System.getenv("password");
     }
-    public static DatabaseConnector getInstance(){
-        if(db_instance == null){
+
+    /**
+     * Returns the singleton instance of the DatabaseConnector.
+     *
+     * @return DatabaseConnector instance
+     */
+    public static DatabaseConnector getInstance() {
+        if (db_instance == null) {
             db_instance = new DatabaseConnector();
         }
         return db_instance;
     }
-    //Connects to database
-    private void connect(){
-        try{
+
+    /**
+     * Connects to the database.
+     */
+    private void connect() {
+        try {
             Class.forName("com.mysql.cj.jdbc.Driver");
             connection = DriverManager.getConnection(host, username, password);
             statement = connection.createStatement();
             canConnect = true;
-        }catch (Exception e){
+        } catch (Exception e) {
             System.out.println(e);
         }
         //System.out.println("Connected successfully");
     }
-    //Disconnects from database
-    private void disconnect(){
-        try{
+
+    /**
+     * Disconnects from the database.
+     */
+    private void disconnect() {
+        try {
             connection.close();
             //System.out.println("DcanConnect successfully");
-        }catch (Exception e){
+        } catch (Exception e) {
             System.out.println(e);
         }
     }
-    //Fetches all data from database and puts them in an ArrayList
-    public ArrayList<QA> fetchAllData(){
+
+    /**
+     * Fetches all data from the database and puts them in an ArrayList.
+     *
+     * @return ArrayList of QA objects fetched from the database
+     */
+    public ArrayList<QA> fetchAllData() {
         connect();
         qas = new ArrayList<>();
-        try{
+        try {
             ResultSet resultSet = statement.executeQuery("select * from QA");
-            while (resultSet.next()){
+            while (resultSet.next()) {
                 qas.add(new QA(resultSet.getInt(1), QAManager.parseQuestion(resultSet.getString(2)), resultSet.getString(3)));
             }
             return qas;
-        }catch (Exception e){
+        } catch (Exception e) {
             System.out.println(e);
-        }finally {
+        } finally {
             disconnect();
         }
         return null;
     }
-    //Adds Question and Answer to database
-    public void addQA(String question, String answer){
+
+    /**
+     * Adds a question and answer to the database.
+     *
+     * @param question The question to be added
+     * @param answer   The answer to be added
+     */
+    public void addQA(String question, String answer) {
         connect();
-        if(question.length() > 255 || answer.length() > 255 || question.length() == 0 || answer.length() == 0) return;
-        try{
+        if (question.length() > 255 || answer.length() > 255 || question.length() == 0 || answer.length() == 0) return;
+        try {
             statement.executeUpdate("INSERT INTO `QA`(`Question`, `Answer`) VALUES ('" + question + "','" + answer + "')");
             System.out.println("Question added successfully");
-        }catch (Exception e){
+        } catch (Exception e) {
             System.out.println(e);
-        }finally {
+        } finally {
             disconnect();
         }
     }
-    public void updateQA(int id, String question, String answer){
+
+    /**
+     * Updates a question and answer in the database by ID.
+     *
+     * @param id       The ID of the question and answer to update
+     * @param question The updated question
+     * @param answer   The updated answer
+     */
+    public void updateQA(int id, String question, String answer) {
         connect();
-        try{
+        try {
             statement.executeUpdate("UPDATE QA SET Question = '" + question + "', Answer = '" + answer + "' WHERE ID = " + id);
             System.out.println(id + " updated successfully");
-        }catch (Exception e){
+        } catch (Exception e) {
             System.out.println(e);
-        }finally {
+        } finally {
             disconnect();
         }
     }
-    //Removes Question and Answer from database
-    public void removeQA(int id){
+
+    /**
+     * Removes a question and answer from the database by ID.
+     *
+     * @param id The ID of the question and answer to remove
+     */
+    public void removeQA(int id) {
         connect();
-        try{
+        try {
             statement.executeUpdate("DELETE FROM QA WHERE ID = " + id);
             System.out.println(id + " removed successfully");
-        }catch (Exception e){
+        } catch (Exception e) {
             System.out.println(e);
-        }finally {
+        } finally {
             disconnect();
         }
     }
-    //Login
+
+    /**
+     * Verifies login credentials of an admin.
+     *
+     * @param username The admin's username
+     * @param password The admin's password
+     * @return true if the credentials are correct, false otherwise
+     */
     public boolean login(String username, String password) {
         connect();
         try {
@@ -115,16 +172,21 @@ public class DatabaseConnector {
                 System.out.println("Login successful");
                 return true;
             }
-        } catch(Exception e) {
+        } catch (Exception e) {
             System.out.println(e);
-        }
-        finally {
+        } finally {
             disconnect();
         }
         System.out.println("Incorrect Username or Password");
         return false;
     }
-    //Creates new Admin to the database
+
+    /**
+     * Creates a new admin in the database.
+     *
+     * @param username The admin's username
+     * @param password The admin's password
+     */
     public void newAdmin(String username, String password) {
         connect();
         byte[] salt = Password.getSalt();
@@ -138,13 +200,18 @@ public class DatabaseConnector {
             statement.setBlob(3, saltBlob);
             statement.executeUpdate();
             System.out.println("Created new Admin: " + username);
-        }catch(Exception e) {
+        } catch (Exception e) {
             System.out.println(e);
-        }finally {
+        } finally {
             disconnect();
         }
     }
 
+    /**
+     * Checks if the connector can connect to the database.
+     *
+     * @return true if the connector can connect, false otherwise
+     */
     public boolean canConnect() {
         return canConnect;
     }