Sonic Java Programming Exercise

This is a very simple coding example, no complicated algorithms. Our intent is to collect an example of your design and code so that we can discuss your approach to fulfilling the requirements. The purpose is to generate further discussion and explore your grasp of OO concepts and knowledge of the JDK. Present your response as you see fit.

Program requirements:

You are working on a team developing an e-commerce application. One of your tasks is to complete the implementation of the Order class that an intern has started along with any other class or classes on which it depends.

The Order constructor requires an array of OrderItems.

1. The business rules dictate that there are two types of order items required, service and material. There is one distinction between them, only material items are taxable. An instance of an OrderItem is only required to contain an Item and a quantity.

2. An Order, once constructed, is immutable (no one should be able to change it).

3. The Order object also needs to be Serializable as it will be distributed across multiple VM’s.

4. It is critical that the method that returns the order-total returns accurately to the nearest penny.

5. There is an expected future requirement that Items be used as keys in a Hashtable so address this issue now.

6. Make any changes needed to the Order object to meet the requirements stated above, although you should not have to add any more public methods.

7. This API will be used by many developers so implement all common methods.

Here is the partially implemented code:

package com.exam;

/**
 * Represents a part or service that can be sold.
 *
 * care should be taken to ensure that this class is immutable since it
 * is sent to other systems for processing that should not be able to    
 * change it in any way.
 *
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: Exams are us</p>
 * @author Joe Blow
 * @version 1.0
 */
public class Item 
{
  private Integer key;
  private String name;
  private float price;
  
  public Item(Integer key, String name, float price) 
  {
    this.key = key;
    this.name = name;
    this.price = price;
  }
  
  public Integer getKey()
  {
    return key;
  }

  public String getName()
  {
    return name;
  }

  public float getPrice()
  {
    return price;
  }
}


package com.exam;

import java.util.*;

/**
 * Represents and Order that contains a collection of items.
 *
 * care should be taken to ensure that this class is immutable since it
 * is sent to other systems for processing that should not be able 
 * to change it in any way.
 *
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: Exams are us</p>
 * @author Joe Blow
 * @version 1.0
 */
public class Order
{
  private OrderItem[] orderItems;

  public Order(OrderItem[]orderItems)
  {
    this. orderItems = orderItems;
  }

  // Returns the total order cost after the tax has been applied
  public float getOrderTotal(float taxRate)
  {
    return 0; // implement this method
  }

  /**
   * Returns a Collection of all items sorted by item name
   * (case-insensitive).
   *
   * @return Collection
   */
  public Collection getItems()
  {
    return null;  // implement this method
  }
}