This isn't really the forum you want to ask that question in - properties are part of the basic
Java system. However, the normal use would be to load properties, use them, add/update properties, then save them. You'd normally create an OutputStream on the same file you loaded from to write the updated properties on.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.