gistfile1.java

	private static Map<String, Integer> ips = new HashMap<String, Integer>();
	@EventHandler
	public void onPlayerJoin(PlayerLoginEvent event)
	{
		if (!event.getResult().equals(Result.ALLOWED)) return;
		final String addy = event.getAddress().toString();
		if (ips.containsKey(addy))
		{
			if (ips.get(addy) > 4)
			{
				event.setResult(Result.KICK_OTHER);
				event.setKickMessage("Too many players from your IP are logged in!");
			}
			else
			{
				ips.replace(addy, ips.get(addy)+1);
			}
		}
		else
		{
			ips.put(addy, 1);
		}
	}
	@EventHandler
	public void onPlayerQuit(PlayerQuitEvent event)
	{
		final String addy = event.getPlayer().getAddress().toString();
		if (ips.get(addy) == 1)
		{
			ips.remove(addy);
		}
		else
		{
			ips.replace(addy, ips.get(addy)-1);
		}
	}