Java If-else 함수가 올바르게 작동하지 않음

저는 Java 및 MySQL을 처음 사용하며 IF 함수에 문제가 있지만 현재 할당을 완료하려고합니다. MySQL의 쿼리 결과를 고객 ID를 기반으로 콘솔에 인쇄하고 고객 ID가 없으면 오류 메시지를 표시하고 싶습니다.

데이터베이스에서 ID가 발견되면 데이터가 표시되지만 ID가 없으면 아무 일도 일어나지 않습니다. 어떤 도움이라도 대단히 감사하겠습니다!

package cos106_assignment_april2015;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.sql.*;
import javax.swing.border.*;


public class ProductSearch {

JFrame f = new JFrame("Ray Sport Inc. | Product Search");
JTextField custIDF;

public ProductSearch() {
  JLabel search1, customer, empty;
    search1 = new JLabel("Enter Customer ID number to search for a customer's product records. Results print to console.");
    customer = new JLabel("Customer ID:");
    empty = new JLabel("");

  custIDF = new JTextField();

  JButton search, back;
    search = new JButton("Search");
    back = new JButton("Back to Menu");

  search.addActionListener(new ActionListener() {
    public void actionPerformed (ActionEvent e){

    String custID = custIDF.getText();

    try { 
    System.out.println("Establishing connection to the MySQL Database...");
    Connection conn = null;
    Statement stmt =null;
    String url = "jdbc:mysql://localhost:3306/raysportdb";
    String driver = "com.mysql.jdbc.Driver";
    String userName = "root"; 
    String password = "password";
    Class.forName(driver).newInstance();
    conn = DriverManager.getConnection(url,userName,password);
    stmt = conn.createStatement();
    System.out.println("Connection established. Connected to the customer and item records.");

        String sql = "select a.Customer_ID, c.Order_ID, b.Product_ID, \n" +
                     "b.Product_Name, b.Product_Type, c.Order_Quantity \n" +
                     "from customer a, product b, orders c \n" +
                     "where a.Customer_ID = '"+custID+"' and b.Product_ID = c.Product_ID \n" +
                     "and b.Product_Type = c.Product_Type_FK and a.Customer_ID = c.Customer_ID \n" +
                     "group by c.Order_ID order by a.Customer_ID";  

        ResultSet result = stmt.executeQuery(sql);
         while(result.next()){
             String cid = result.getString("a.Customer_ID");
            if (custID.equals (cid)) {

                String f2 = result.getString("c.Order_ID");
                String f3= result.getString("b.Product_ID");
                String f4 = result.getString("b.Product_Name");
                String f5 = result.getString("b.Product_Type");
                String f6 = result.getString("c.Order_Quantity");

                System.out.println("");
                System.out.println("Customer ID\t:"+ cid); 
                System.out.println("Order ID\t:" + f2);
                System.out.println("Product ID\t:" + f3);
                System.out.println("Product Name\t:" + f4);
                System.out.println("Product Type\t:" + f5);
                System.out.println("Order Quantity\t:" + f6);
                System.out.println("");
                                  }
            else {
                JOptionPane.showMessageDialog(null, "Customer ID does not exist!", "Error", JOptionPane.ERROR_MESSAGE);
                System.out.println("Customer ID does not exist in the database.");
                 }
           }
      conn.close();
    }

    catch (Exception err) {
       System.err.println("Error:"+ err.getMessage());
                            }}});


  back.addActionListener(new ActionListener() { 
  public void actionPerformed (ActionEvent e){
  new Menu();
  f.setVisible(false);}});

  JPanel p = new JPanel();
  p.setLayout(new GridLayout(6,2));
  p.setBorder(new TitledBorder("Product Search"));
  p.add(search1);
  p.add(empty);
  p.add(customer);
  p.add(custIDF);
  p.add(search);
  p.add(back);

  f.getContentPane().add(p);
  f.pack(); 
  f.setSize(585,284);
  f.setLocationRelativeTo(null);
  f.setVisible(true);
  f.setResizable(false);
  f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);



}

public static void main(String ar[]){

new ProductSearch();
 } 
}