IPRestrict.java

// IPRestrict.java

package com.wolfy9247.iprestrict;

import java.util.logging.Logger;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.configuration.file.FileConfiguration;
import org.bukkit.plugin.PluginDescriptionFile;
import org.bukkit.plugin.java.JavaPlugin;

public class IPRestrict extends JavaPlugin {
    public static IPRestrict instance;
    protected FileConfiguration config;

    public final Logger log = Logger.getLogger("Minecraft");
    public static String logTag = "[AdminIP] ";

    @Override
    public void onDisable() {
        PluginDescriptionFile pdfFile = this.getDescription();
        log.info(logTag + pdfFile.getName() + " v" + pdfFile.getVersion() + " disabled!");
    }

    @Override
    public void onEnable() {
        instance = this;
        PluginDescriptionFile pdfFile = this.getDescription();
        getConfig().options().copyDefaults(true);
        saveConfig();
        new IPRestrictJoinListener(this);
        registerCommands();
        log.info(logTag + pdfFile.getName() + " v" + pdfFile.getVersion() + " enabled!");
    }

    private void registerCommands() {

    }

    public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args) {
        if(!cmd.isRegistered()) {
            return false;
        }
        else if(commandLabel.equalsIgnoreCase("ipr")) {
            for(int i = 0; i < 3; i++) {
                if(args[i].isEmpty()) {
                    return false;
                }
            }
            if(args[0] == "set") {
                if(Bukkit.getPlayer(args[1]) == null) {
                    sender.sendMessage(ChatColor.RED + "The player you have entered is invalid!");
                    return false;
                }
                Object[] playerIPs = getConfig().getList(instance + "." + sender.getName()).toArray();
                int lastIndex = playerIPs.length + 1;
                getConfig().set(instance + "." + sender.getName(), args[2]); // Need to figure out how to set next line "-";

                return true;
            }
            else if(args[0] == "remove") {
                if(Bukkit.getPlayer(args[1]) == null) {
                    sender.sendMessage(ChatColor.RED + "The player you have entered is invalid!");
                    return false;
                }
                // Figure out how to remove a line if found.
            }
            return false;
        }
        return true;
    }
}

// IPRestrictJoinListener.java

package com.wolfy9247.iprestrict;

import java.net.InetSocketAddress;

import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerJoinEvent;

public class IPRestrictJoinListener implements Listener {
    public static IPRestrict plugin;

    public IPRestrictJoinListener(IPRestrict plugin) {
        plugin.getServer().getPluginManager().registerEvents(this, plugin);
    }

    @EventHandler
    void onPlayerJoin(PlayerJoinEvent event) {
        Player player = event.getPlayer();
        InetSocketAddress joinIP = event.getPlayer().getAddress();
        Object[] playerIPs = plugin.getConfig().getList(plugin + "." + player.getName()).toArray();

        for(int i = 0; i < playerIPs.length; i++) {
            if(joinIP != playerIPs[i]) {
                if(player.isOp()) {
                    return;
                }
                else {
                    player.kickPlayer(plugin.getConfig().getString("IPRestrict.Kick Message"));
                }
            }
            else {
                return;
            }
        }
    }
}