Java provides methods for saving data permanently. An object that has to be saved has to implement the interface Serializable. But there is one problem with Java's object serialization: The objects can not be changed. If I open such a file, i see some cryptic symbols. But sometimes I also want to change the data outside of a program. What is a good way to store objects if I also want to change it's values outside of the program?
Java serialisation is best avoided. It's full of possible security exploits, it doesn't cope well when your class structure is changed and it creates a "hidden" constructor in your class.
It sounds like you want to be able to use some sort of text file format for storing your objects. I would suggest using JSON or XML. But be very careful when reading these files back in - since they can be edited, they should be viewed as untrusted, and you should be very very strict about checking the contents.