(Java) Saving/Loading an ArrayList using Properties

Question

I have been researching different methods for saving and loading configuration settings for my application. I've looked into Preferences, JSON, Properties and XML but I think I've settled on using the Properties method for most of my application settings.

However, I'm not able to find any information on how to best save and load an ArrayList from that file. It seems there are only individual key/pair string combinations possible.

So my question is basically, is there a better way to do this? I have an ArrayList of Strings in my application that I need to be able to save and load. Can this be done with Properties or do I need to use a separate file just to hold this list and then read it in as an ArrayList (per line, perhaps)?

EDIT: I should mention, I would like to keep all config files as readable text so I am avoiding using Serialization.

Answer 1

You can use commas to place multiple values on the same key.

key:value1,value2,value3

Then split them using the split function of a string after reading them in which will give you a String[] array which can be turned into an ArrayList via Arrays.asList().

Here's a partial MCVE:

ArrayList<String> al = new ArrayList<>();
al.add("value1");
al.add("value2");
al.add("value3");

String values = al.toString();
//Substring used to get rid of "[" and "]" 
prop.setProperty("name",values.substring(1,values.length() - 1);

Answer 2

I found that using the following combination worked perfectly in my case.

Save:

String csv = String.join(",", arrayList());
props.setProperty("list", csv);

This will create a String containing each element of the ArrayList, separated with a comma.

Load:

arrayList = Arrays.asList(csv.split(","));

Takes the csv String and splits it at each comma, adding the elements to the arrayList reference.