package com.interview.design.pattern.other;

/**
 * Created_By: stefanie
 * Date: 14-12-3
 * Time: 下午6:18
 *
 * In Null Object pattern, a null object replaces check of NULL object instance.
 * Instead of putting if check for a null value, Null Object reflects a do nothing relationship.
 * Such Null object can also be used to provide default behaviour in case data is not available.
 * In Null Object pattern, we create a abstract class specifying the various operations to be done,
 * concreate classes extending this class and a null object class providing do nothing implemention of this class
 * and will be used seemlessly where we need to check null value.
 *
 * Used in Python, Groovy, NULL object
 */
public class NonObjectPattern {

    static abstract class AbstractCustomer {
        protected String name;
        public abstract boolean isNil();
        public abstract String getName();
    }

    static class RealCustomer extends AbstractCustomer {

        public RealCustomer(String name) {
            this.name = name;
        }

        @Override
        public String getName() {
            return name;
        }

        @Override
        public boolean isNil() {
            return false;
        }
    }

    static class NullCustomer extends AbstractCustomer {

        @Override
        public String getName() {
            return "Not Available in Customer Database";
        }

        @Override
        public boolean isNil() {
            return true;
        }
    }

    static class CustomerFactory {

        public static final String[] names = {"Rob", "Joe", "Julie"};

        public static AbstractCustomer getCustomer(String name){
            for (int i = 0; i < names.length; i++) {
                if (names[i].equalsIgnoreCase(name)){
                    return new RealCustomer(name);
                }
            }
            return new NullCustomer();
        }
    }

    public static void main(String[] args) {

        AbstractCustomer customer1 = CustomerFactory.getCustomer("Rob");
        AbstractCustomer customer2 = CustomerFactory.getCustomer("Bob");
        AbstractCustomer customer3 = CustomerFactory.getCustomer("Julie");
        AbstractCustomer customer4 = CustomerFactory.getCustomer("Laura");

        System.out.println("Customers");
        System.out.println(customer1.getName());
        System.out.println(customer2.getName());
        System.out.println(customer3.getName());
        System.out.println(customer4.getName());
    }
}