Nontrivial callback example

CallbackExample.java

import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scheduler.BukkitRunnable;

public final class CallbackExample extends JavaPlugin {

    @Override
    public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
        if (args.length > 0) {
            new AsyncRunnable(sender, args[0], new SenderCallbackFacatory() {

                public SenderCallback newInstance(CommandSender sender, String payload) {
                    return new CommandSenderMessenger(sender, payload);
                }

            }, this).runTaskAsynchronously(this);
            return true;
        } else {
            return false;
        }
    }

    private static class AsyncRunnable extends BukkitRunnable {

        private final CommandSender sender;
        private final String url;
        private final JavaPlugin plugin;
        private final SenderCallbackFacatory factory;

        public AsyncRunnable(CommandSender commandSender, String url, SenderCallbackFacatory factory, JavaPlugin plugin) {
            this.sender = commandSender;
            this.url = url;
            this.plugin = plugin;
            this.factory = factory;
        }

        public void run() {
            // not going to load anything
            plugin.getLogger().fine("Going to fetch " + this.url);
            String payload = this.url;

            this.factory.newInstance(sender, payload).runTask(plugin);
        }

    }

    private interface SenderCallbackFacatory {

        SenderCallback newInstance(CommandSender sender, String payload);

    }

    private static abstract class SenderCallback extends BukkitRunnable {

        final protected CommandSender commandSender;
        final protected String payload;

        public SenderCallback(CommandSender commandSender, String payload) {
            this.commandSender = commandSender;
            this.payload = payload;
        }

    }

    private static class CommandSenderMessenger extends SenderCallback {

        CommandSenderMessenger(CommandSender commandSender, String payload) {
            super(commandSender, payload);
        }

        public void run() {
            commandSender.sendMessage(payload);
        }

    }

}