[hardwired]

Code:

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class MapCombo {
    private JPanel getContent() {
        final Map<String, Customer> map = getMap();
        JComboBox combo = new JComboBox();
        Set<String> keys = map.keySet();
        Iterator<String> it = keys.iterator();
        while(it.hasNext()) {
            String key = it.next();
            combo.addItem(key);
        }
        combo.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JComboBox combo = (JComboBox)e.getSource();
                String key = (String)combo.getSelectedItem();
                Customer customer = map.get(key);
                System.out.println(customer);
            }
        });
        JPanel panel = new JPanel();
        panel.add(combo);
        return panel;
    }

    private HashMap<String, Customer> getMap() {
        Customer[] customers = new Customer[4];
        customers[0] = new Customer("Helen", "Oregon", 12);
        customers[1] = new Customer("Paul",  "Idaho",  99);
        customers[2] = new Customer("Sue",   "Texas",  22);
        customers[3] = new Customer("Oscar", "Utah",   42);
        HashMap<String, Customer> map = new HashMap<String, Customer>();
        for(int i = 0; i < customers.length; i++) {
            String key = customers[i].name;
            Customer value = customers[i];
            map.put(key, value);
        }
        return map;
    }

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new MapCombo().getContent());
        f.setSize(200,100);
        f.setVisible(true);
    }
}

class Customer {
    String name;
    String location;
    int idNumber;

    Customer(String name, String loc, int id) {
        this.name = name;
        location = loc;
        idNumber = id;
    }

    public String toString() {
        return "Customer[name:" + name +
                       " location:" + location +
                       " idNumber:" + idNumber + "]";
    }
}