How to overwrite (save) a file when it has been edited?

I am currently developing a small data management application and would like to have another "Save" entry besides the existing "Save as -> XML / CSV" menu items.

This entry should overwrite the last loaded file with the changed data without opening a dialog again (like in MS Excel or Word).

Of course I have already done some research, but didn't find anything suitable or searched for the wrong one.

These entries and functions I already have and they work:

MenuItem saveXML = new MenuItem("Save as XML");
saveXML.setOnAction((e) -> {
// save file as XML
});

MenuItem saveCSV = new MenuItem("Save as CSV");
saveCSV.setOnAction((e) -> {
// save file as CSV
});

I would like to create this entry:

MenuItem save = new MenuItem("Save");
saveCSV.setOnAction((e) -> {
// Save the last opened document in the same format (XML or CSV) without any dialog
});

This is my application

As Abra suggested, you must remember the location of the most recently loaded file by storing it in a private field:

private File currentFile;

Then you set it whenever you load a file:

MenuItem load = new MenuItem("Load");
load.setOnAction(e -> {
    FileChooser chooser = new FileChooser();
    // (set FileChooser's title and filters here)
    File file = chooser.showOpenDialog(stage);
    if (file != null) {
        // (load file into application)
        this.currentFile = file;
    }
});

Now, you can use that currentFile value to save:

MenuItem save = new MenuItem("Save");
save.setOnAction(e -> {
    if (currentFile != null) {
        // (write to currentFile)
    } else {
        // New file;  ask user for save location.

        FileChooser chooser = new FileChooser();
        // (set FileChooser's title and filters here)
        File file = chooser.showSaveDialog(stage);
        if (file != null) {
            // (save file as CSV or XML depending on chosen filter)
            this.currentFile = file;
        }
    }
});

You may want to move your save logic into private methods, if you haven’t already.

I have a solution that works for me. It may not be the optimal solution, but it could still be useful.

I pass a property to my menuItem that contains the path of my file .put("FILE_LOCATION",..) and use this property in the save-event to select the last path.

Since I also want to save automatically as either CSV or XML file, I delete the path from the variable that contains the other one, if it exists. .remove("FILE_LOCATION")

loadCSV.setOnAction(e -> {
		...
		File f = fileChooser.showOpenDialog(null);
		loadCSV.getProperties().put("FILE_LOCATION", f.getAbsolutePath());
		loadXML.getProperties().remove("FILE_LOCATION");
});

Then I check which variable is filled and then run the respective method.

save.setOnAction(e -> {
		try {
			if (loadCSV.getProperties().isEmpty() == false) {
				File saveCSV = new File(loadCSV.getProperties().get("FILE_LOCATION").toString());
				if (saveCSV != null) {
					CSV.writeCSV(saveCSV, DataHandler.INSTANCE.foodlist());
				}
			} else if (loadXML.getProperties().isEmpty() == false) {
				File saveXML = new File(loadXML.getProperties().get("FILE_LOCATION").toString());
				if (saveXML != null) {
					XML.writeXMLList(saveXML, DataHandler.INSTANCE.foodlist());
				}
			}
	});