Modifying the Inventory Program

The files UpdateInventory.java and InventoryItem.java are modifications of
Listings 8.7 and 8.8 in the text. Currently UpdateInventory does the same
thing the CheckInventory program in Listing 8.7 does -- it reads a list of
inventory items in from a file (the file inventory.dat), stores them in an
array of objects of type InventoryItem and then prints the contents of the
array.

Compile and run the program to see how it works.

In this exercise you will modify the program to "restock" the inventory
then write the revised inventory data back to the inventory.dat file. To
restock the program will read in (from standard input) the number of
additional units of each item then add that number to the current number of
units (the instance variable units in the InventoryItem class). To
accomplish this, the InventoryItem class has four methods that are not
included in Listing 8.8. They are

   * restock -- which takes a single parameter representing the number of
     units of the item to be added to the inventory. That number is added
     to the units instance variable.
   * three accessor methods getName, getUnits, and getPrice that return the
     name, number of available units, and the price, respectively, of the
     inventory item

Modify UpdateInventory.java as follows:

  1. In the loop before the current println statement,
       a. Prompt for the number of additional units of the item (use the
          getName method in the prompt so the user knows the name of the
          item).
       b. Read the number in (use the InputStreamReader and BufferedReader 
          classes.)
       c. Update the units of the item in inventory (use the restock
          method).
  2. Compile and run what you have so far.
  3. Now add code to write the inventory back to the inventory.dat file. To
     do this,
       a. Set up the output file stream (Listing 8.9 contains an example)
          before the loop (but after the file for reading has been closed).
       b. In the loop, write the item to the output file in the same format
          as the original input file (use the accessor methods).
       c. Close the output file stream after the loop.
  4. Compile and run the program. Look at the contents of file inventory.dat
     to make sure the file has been updated.