public class MyPlugin extends JavaPlugin {
    private MyConfig myConfig;
    private ConfigFactory configFactory = ConfigFactory.newFactory(this);

    @Override
    public void onEnable() {
        myConfig = configFactory.fromFile("config", MyConfig.class);
        getLogger().info(myConfig.getStartMessage());

        if (myConfig.myFavouriteNumbers != null) {
            getLogger().info(myConfig.myFavouriteNumbers.toString());
        }
    }

    @Override
    public void onDisable() {
        // if we changed values in my config while the server is up
        // we should save it
        configFactory.save("config", myConfig);
    }
}

@Comment("This is my header comment")
public class MyConfig {
                    // init values will be saved as part of the "default config"
    private String startMessage = "This awesome bukkit plugin has started!";
    @Comment("Put in your favourite number here!")
    @RequiredField // if this field is not set in the config file due to user error
                   // an exception will be thrown
    private int myFavouriteNumber = 3;
                   // lists, sets, queues, maps, and arrays are supported!
    List<Integer> myFavouriteNumbers;
                   // supports concurrency classes!
    private AtomicInteger myFavouriteAtomicNumber = new AtomicInteger(4);
                   // myWeapon will be set if it's in the config but won't exist
                   // by default
    private ItemStack myWeapon;
                   // additionally objects within the config are allowed
    private PartOfConfig part;

    public String getStartMessage() {
        return startMessage;
    }
}

public class PartOfConfig {
    private String hi = "my name is billy";
}