1. The new readFromDisk method only reads the disk and stores the read
object in a private class variable. The method returns true if the read
was successful (file exists, etc.) or false if the read operation
failed. 2. In order to get the Contact list, main needs to invoke a new
method getObjectFromDiskFile. 3. This can be done in a single operation 
if (readFromDisk)    contactList = getObjectFromDiskFile();