Abstract class Customer﹛
    protected String name;
    (1) boolean isNil();
    (2) String getName();
﹜

class RealCustomer(3) Customer {
		public RealCustomer(String name) {
			this.name = name;
		}
		public String getName() {
			return name;
		}
		public boolean isNil() {
			return false;
		}
﹜

class NullCustomer(4) Customer﹛

    public String getName()﹛ return "Not Available in Customer Database";﹜
    public boolean isNil()﹛ return true;﹜

﹜

class Customerfactory {
    public String[] names = {
        "Rob"，
        "Joe"，
        "Julie"
    };
    public Customer getCustomer(String name) {
            for(int i = 0; i
                if(names[i].(5))﹛ return new RealCustomer(name);﹜﹜
                return(6);
            ﹜
    ﹜ 
                
                
public class CrM﹛ 
    public void getCustomer()﹛ 
        Customerfactory(7); 
        Customer customer1 - cf.getCustomer("Rob"); 
        Customer customer2 = cf.getCustomer("Bob"); 
        Customer customer3 = cf.getCustomer("Julie"); 
        Customer customer4 = cf.getCustomer("Laura"); 
        System.out.println("customers”)
        System.out.println(customer1.getName()); 
        System.out.println(customer2getName()); 
        System.out.println(customer3.getName()); 
        System.out.println(customer4.getName());
    ﹜ 
    
    public static void main(String[] arge)﹛ 
        CRM crm = new CRM(); 
        Crm.getCustomer();
    ﹜
﹜


/*程序输出为：
Customers
rob
Not Available in Customer Database
Julie
Not Available in Customer Database
*/