External Interfaces/API

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.

Running the serialexample Program

Description of Function phonebook