Java Security

How do I save an object such as a SecretKey to a file, shut down the program, restart the program, and then recreate the SecretKey object?

The program that I am writing creates an encryption object and encrypts password information and then stores it in a file. The program will sometimes be terminated by the user, so I need a way of saving the SecretKey to a file. When the program starts again it will construct an encryption object using a SecretKey as a parameter. I would like to use the information for the SecretKey from the file that was saved prior to the program's termination, so that the encrypted passwords can be decrypted and loaded into memory.

Thanks,
Steve