Plugin error IISeanII

package me.IISeanII.spakwarp;

import java.util.logging.Logger;

import org.bukkit.ChatColor;
import org.bukkit.Location;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.plugin.PluginDescriptionFile;
import org.bukkit.plugin.java.JavaPlugin;


public class spakwarp extends JavaPlugin{
    public final Logger logger = Logger.getLogger("Minecraft");
    public static spakwarp plugin;

    PluginDescriptionFile pdfFile = this.getDescription();
    public final Location[] warpLocations = new Location[100];
    public final String[] warpName = new String[100];
    int warpCounter = 0;

        @Override
        public void onDisable() {
        this.logger.info(pdfFile.getName() + " Has Been Disabled!");
    }

    @Override
    public void onEnable() {
        PluginDescriptionFile pdfFile = this.getDescription();
        this.logger.info(pdfFile.getName() + " Version " + pdfFile.getVersion() + " Has Been Enabled!");
    }

    public boolean onCommand(CommandSender sender, Command cmd,
            String commandLabel, String[] args){
        Player player = (Player) sender;
        if(commandLabel.equalsIgnoreCase("setswarp")){
            if(args.length ==0){
                player.sendMessage(ChatColor.RED + "/setswarp <swarpname>");
            }else{
                Location location = player.getLocation();
                if(!(warpCounter > 100)){
                    warpLocations[warpCounter] = location;
                    warpName[warpCounter] = args[0];
                    warpCounter++;
                    player.sendMessage(ChatColor.GREEN + "Swarp Set As: " + args[0]);
                }else{
                    player.sendMessage(ChatColor.RED+"Swarp Limit Exceeded! Unable To Create Warp!");

                }
            }
        }  else if(commandLabel.equalsIgnoreCase("swarp")){
            for(int i = 0; i < warpName.length; i++){
                String warpname = warpName[i];
                if(args[0].equalsIgnoreCase(warpName)){
                    Location warpLocation = warpLocations[i];
                    player.teleport(warpLocation);
                    player.sendMessage(ChatColor.GREEN +"You are now at "
                            + warpName);
                    break;
                }
        }
    } else if(commandLabel.equalsIgnoreCase("swarp list")){
        String warps = "";
        for(int i = 0; i <warpName.length; i++){
            if(i != warpName.length){
                warps+=warpName[i] + ", ".replace("Null", "");
            }else{
                player.sendMessage(ChatColor.DARK_GRAY + "Swarps List: " + ChatColor.DARK_GRAY );
            }
        }