Lab 6: Exceptions

In this lab, you will get practice creating, throwing, and catching exceptions. This lab will build on the PhoneDirectory class from the previous lab. You will also use inner classes.

Create an inner class of PhoneDirectory called DirectoryFullException. The DirectoryFullException should be a subclass of Exception. Change the add method of PhoneDirectory to throw a DirectoryFullException if it is unable to add the PhoneEntry to the directory because the directory is full. Change the main method that calls the add method to catch the DirectoryFullException and print an appropriate error message.
Change the main method for both the "get" and "lookup" actions to catch a NullPointerException rather than to test for the return value being null.
Change the main method so that if the user enters "print", then the full contents of the PhoneDirectory should be printed. For example, a printing could look like this:
```
  0: Jon Smith, 555-1212
  1: Mary Jane, 555-1234
  3: Sam Lee, 555-9876
```
Use a loop that starts at index 0 and calls get(index) to get the PhoneEntry at each possible index. The loop should print the PhoneEntry value that is returned. The loop should catch a NullPointerException, print nothing if such an exception occurs, and move on to try the next index. To do this, you may need to change the code that builds the string you will print so that it calls the toString method of the PhoneEntry object directly. That is, if you have a PhoneEntry e, and if your code has something like System.out.println("entry is " + e); then you will have to change it to System.out.println("entry is" + e.toString());. The routine should also catch an ArrayIndexOutOfBoundsException which indicates that the index tested is beyond the length of the directory, and when the exception occurs the loop should terminate.

When you are finished, email your code to me.