//CONTROLLER
public int modifyCustomer(Customer customer) {
            int result = -1;
            try {
                PreparedStatement stmt;
                if (customer.hasFirstName() && !customer.hasLastName()) { // Has firstName and does NOT have lastName
                    stmt = con.prepareStatement("UPDATE Customer SET first_name = ? where customer_ID = ?");
                    stmt.setString(1, customer.getFirstName());
                    stmt.setString(2, customer.getLastName());
                    result = stmt.executeUpdate();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return result;
        }

//USER INTERFACE
public void displayModifyCustomerRecordsMenu() {
    	Customer cusFilters = new Customer();
    	boolean validInput = false;
    	boolean sameMenu = true;
    	String first_name = "";
    	String last_name = "";
    	String address1 = "";
    	String address2 = "";
    	int zone_ID = 0;
    	while (sameMenu) {
            System.out.println("Modify Customer Records");
            printCurrentCustomerFilters(cusFilters);
            System.out.println("4. Reset Filters");
            System.out.println("5. Modify using current filters");
            System.out.println("6. Back\n");
            System.out.print("Enter your choice: ");
            if (input.hasNext()) {
                int choice = input.nextInt();

				switch (choice) {
                case 1:
			    	while (!validInput) {
			    		System.out.println("First Name or press i to not modify: ");
			           	if(input.hasNext()){
			           			first_name = input.nextLine();
			           			if(first_name != null && first_name != "") {
			           			validInput = true;
			           			cusFilters.setFirstName(first_name);
			           		}
			           	}
			    	}
			    	validInput = false;
			    	break;

                case 2:
			    	while (!validInput) {
			    		System.out.println("Last Name: ");
			        	if(input.hasNext()){
			        			last_name = input.nextLine();
				       			if(last_name != null && last_name != "") {
				       			validInput = true;
				       			cusFilters.setLastName(last_name);
				       		}
			        	}
			    	}
			    	validInput = false;
			    	break;

                case 3:
			    	while (!validInput) {
			    		System.out.println("Address 1: ");
			        	if(input.hasNext()){
			        			address1 = input.nextLine();
				       			if(address1 != null && address1 != "") {
				       			validInput = true;
				       			cusFilters.setAddress1(address1);
			       			}
			        	}
			    	}
			    	validInput = false;
			    	break;

                case 4:
			    	while (!validInput) {
			    		System.out.println("Address 2: ");
			        	if(input.hasNext()){
			        			address2 = input.nextLine();
				       			if(address2 != null && address2 != "") {
				       			validInput = true;
				       			cusFilters.setAddress2(address2);
			       			}
			        	}
			    	}
			    	validInput = false;
			    	break;

                case 5:
			    	while (!validInput) {
			    		System.out.println("Zone ID: ");
			        	if(input.hasNext()){
			        			zone_ID = input.nextInt();
				       			if(zone_ID >= 0 && zone_ID <= 65535) {
				       			validInput = true;
				       			cusFilters.setZone_ID(zone_ID);
			       			}
			        	}
			    	}
			    	break;
                case 6: // Reset Filters
                    sameMenu = true;
                    cusFilters = new Customer(); // Re-initialises filters object
                    System.out.println("Filters Reset!");
                    break;
                case 7: // Modify
                    int result = controller.modifyCustomer(cusFilters);
                    if (result != -1) {
                        System.out.println("Successfully modified " + result + " rows");
                    } else {
                        System.out.println("Failed to modify rows.");
                    }
                    sameMenu = false;
                    displayDeliveryMenu(); // Go back to deliveryMenu()
                    break;
                case 8: // Back
                    sameMenu = false;
                    displayDeliveryMenu(); // Go back to deliveryMenu()
                    break;
            }
            if (choice < 1 || choice > 8) { // TODO: Null & empty checks
                System.out.println("Please enter a number between 1 and 8.");
            }
        } else {
            // Clear the input buffer and start again
            input.nextLine();
            System.out.println("You entered an invalid choice, please try again...");

            }
	    	// Assuming all fields are valid
	    	controller.addCustomer(cusFilters);
    	}
    }