Passing List of class objects to config file

I have got class:

class Region{
String name;
List<String> BlockPlayers = new ArrayList<>();
}

Then I made a List of objects in my program like this

List<Region> playersRegions = new ArrayList<>();

Now I need to make a function that will pass objects from playersRegions list to config file. Then I need to make function that will load everything from config file and pass to playersRegions list

I have made something like this

private void save_regions_inConfig()
{
getConfig().set("locs", playersRegions);
saveConfig();
}

But I have no idea how to load it from file to playersRegions. I just want to keep everything after I close the program and open it once more.

You should define a way to format the region.

Let assume method are on your JavaPlugin class and everything else is well made (plugin.yml valid etc)

To write them, use something like this:

public void saveRegion(List<Region> regions) {
   FileConfiguration config = getConfig();
   int i = 0;
   for(Region r : regions) {
       config.set("regions." + i + ".name", r.name);
       config.set("regions." + i + ".blockplayers", r.BlockPlayers);

       i++;
   }
   saveConfig();
}

The config file will be like this:

regions:
   0:
      name: "Region 1"
      blockplayers:
      - "Something"

Now, to read it, you should do something like that:

public List<Region> getRegion() {
   ConfigurationSection config = getConfig().getConfigurationSection("regions");
   if(config == null) // no region set yet
       return new ArrayList<>();
   List<Region> list = new ArrayList<>();
   for(String keys : config.getKeys(false)) {
       ConfigurationSection regionConfig = config.getConfigurationSection(keys);
       list.add(new Region(regionConfig.getString("name"), region.getStringList("blockplayers")));
   }
   return list;
}

Note: you should define a constructor in your Region object like that:

public class Region{
    String name;
    List<String> blockPlayers = new ArrayList<>();

    public Region(String name, List<String> blockPlayers) {
        this.name = name;
        this.blockPlayers = blockPlayers;
    }
}

Finally, some of your name (method or variable) doesn't meet the Java convention. Specially about method, but that's a detail.