Java File Chooser

I have a program that successfully uses FileChooser in java fx to select and display an image file. I need to expand the program to select a directory and display all the jpg files in that directory automatically and save them.

I know how to select a directory, but it gives me only the path name.

I know that I can use filechooser's extension filter to select only jpg files.

What I am completely clueless about is how to actually have my program retrieve all the files and save them in my program.