User`s manual

Example – Creating and Using a Phone Book
5-73
Example – Creating and Using a Phone Book
The example’s main function, phonebook, can be called either with no
arguments, or with one argument, which is the key of an entry that exists in
the phone book. The function first determines the directory to use for the phone
book file.
If no phone book file exists, it creates one by constructing a
java.io.FileOutputStream object, and then closing the output stream. Next,
it creates a data dictionary by constructing an object of the Java API class,
java.util.Properties, which is a subclass of java.util.Hashtable for
storing key/value pairs in a hash table. For the
phonebook program, the key is
a name, and the value is one or more telephone numbers.
The
phonebook function creates and opens an input stream for reading by
constructing a
java.io.FileInputStream object. It calls load on that object to
load the hash table contents, if it exists. If the user passed the key to an entry
to look up, it looks up the entry by calling
pb_lookup, which finds and displays
it. Then, the
phonebook function returns.
If
phonebook was called without the name argument, it then displays a textual
menu of the available phone book actions:
•Look up an entry
•Add an entry
•Remove an entry
•Change the phone number(s) in an entry
•List all entries
The menu also has a selection to exit the program. The function uses MATLAB
functions to display the menu and to input the user selection.
The
phonebook function iterates accepting user selections and performing the
requested phone book action until the user selects the menu entry to exit. The
phonebook function then opens an output stream for the file by constructing a
java.io.FileOutputStream object. It calls save on the object to write the
current data dictionary to the phone book file. It finally closes the output
stream and returns.