NullPointerException

Im pretty new to coding, but i had ago at a warn plugin. After testing i keep getting this error on console after i do the command to warn someone.

Code:

[19:41:12 ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'warn' in plugin SimpleWarn v1
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:196) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at org.bukkit.craftbukkit.v1_7_R1.CraftServer.dispatchCommand(CraftServer.java:542) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.PlayerConnection.handleCommand(PlayerConnection.java:932) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java:814) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.PacketPlayInChat.a(PacketPlayInChat.java:28) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.PacketPlayInChat.handle(PacketPlayInChat.java:47) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:146) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:655) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
Caused by: java.lang.NullPointerException
    at SW.george.me.Main.onCommand(Main.java:71) ~[?:?]
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    ... 13 more

This is my Main Class:

Code:

package SW.george.me;
 
import java.util.ArrayList;
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.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.AsyncPlayerChatEvent;
import org.bukkit.plugin.PluginDescriptionFile;
import org.bukkit.plugin.java.JavaPlugin;
 
public class Main extends JavaPlugin implements Listener{
   
    public final Logger logger = Logger.getLogger("Minecraft");
   
 
    ArrayList<String> one = new ArrayList<String>();
    ArrayList<String> two = new ArrayList<String>();
    ArrayList<String> mute = new ArrayList<String>();
   
   
    public void onDisable() {
        PluginDescriptionFile pdfFile = this.getDescription();
        this.logger.info(pdfFile.getName() + "  Disabled.");
    }
    public void onEnable() {
        this.getServer().getPluginManager().registerEvents(this, this);
        PluginDescriptionFile pdfFile = this.getDescription();
        logger.info(pdfFile.getName() + " Version " + pdfFile.getVersion() + " Enabled.");
 
    }
 
   
    public String prefix = new String(ChatColor.GREEN + "[SW] ");
 
    @EventHandler
    public void onChat(AsyncPlayerChatEvent e) {
    Player player = e.getPlayer();
        if(mute.contains(player.getName())) {
            e.setCancelled(true);
            player.sendMessage(prefix + ChatColor.DARK_GRAY + "You Are Muted For 10 Minutes For Being Warned 3 Times Within One Hour.");
        } else {
        }
    }
 
   
   
   
   
    @SuppressWarnings("deprecation")
    public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args) {
        Player p = (Player) sender;
       
        StringBuilder str = new StringBuilder();
        for (int i = 2; i < args.length; i++){
        str.append(args[i] + " ");
        }
 
        String message = str.toString();
       
       
        if(cmd.getName().equalsIgnoreCase("Warn")) {
            if(p.hasPermission("Simple.warn")) {
                if(args.length >= 2) {
                    final Player target = this.getServer().getPlayer(args[1]);
                    if(target.isOnline()) {
                        if(!(target.hasPermission("Warn.avoid"))) {
                            if(!(one.contains(target.getName()) && two.contains(target.getName()) && mute.contains(target.getName()))) {
                                one.add(target.getName());
                                target.sendMessage(prefix + ChatColor.DARK_GRAY + "You Were Warned For: " + message + " By: " + ChatColor.GOLD + p.getName());
                                p.sendMessage(prefix + ChatColor.DARK_GRAY + "You Warned: " + ChatColor.GOLD + target.getName() + ChatColor.DARK_GRAY + " For: " + message);
                                p.sendMessage(prefix + ChatColor.DARK_GRAY + "This Was Their 1st Warning, Two More And They Will Be Muted!");
                                target.sendMessage(prefix + ChatColor.DARK_RED + "This Was Your 1st Warning. Two More And You Will Be Muted For 10 Minutes!");
                                Bukkit.broadcastMessage(prefix + ChatColor.GOLD + target.getName() + ChatColor.DARK_GRAY + " Was Warned For " + message + " By: " + p.getName() + ". This Is Their 1st Warning!");
                            }
                            if(one.contains(target.getName())) {
                                one.remove(p.getName());
                                two.add(target.getName());
                                target.sendMessage(prefix + ChatColor.DARK_GRAY + "You Were Warned For: " + message + " By: " + ChatColor.GOLD + p.getName());
                                p.sendMessage(prefix + ChatColor.DARK_GRAY + "You Warned: " + ChatColor.GOLD + target.getName() + ChatColor.DARK_GRAY + " For: " + message);
                                p.sendMessage(prefix + ChatColor.DARK_GRAY + "This Was Their 2nd Warning, One More And They Will Be Muted!");
                                target.sendMessage(prefix + ChatColor.DARK_RED + "This Was Your 2nd Warning. One More And You Will Be Muted For 10 Minutes!");
                                Bukkit.broadcastMessage(prefix + ChatColor.GOLD + target.getName() + ChatColor.DARK_GRAY + " Was Warned For " + message + " By: " + p.getName() + ". This Is Their 2nd Warning!");
                            }
                            if(two.contains(target.getName())) {
                                two.remove(target.getName());
                                mute.add(target.getName());
                                target.sendMessage(prefix + ChatColor.DARK_GRAY + "You Were Warned For: " + message + " By: " + ChatColor.GOLD + p.getName());
                                p.sendMessage(prefix + ChatColor.DARK_GRAY + "You Warned: " + ChatColor.GOLD + target.getName() + ChatColor.DARK_GRAY + " For: " + message);
                                p.sendMessage(prefix + ChatColor.DARK_GRAY + "This Was Their 3rd Warning, They Are Now Muted.");
                                target.sendMessage(prefix + ChatColor.DARK_RED + "This Was Your 3rd Warning. You Are Now Muted For 10 Minutes!");
                                Bukkit.broadcastMessage(prefix + ChatColor.GOLD + target.getName() + ChatColor.DARK_GRAY + " Was Warned For " + message + " By: " + p.getName() + ". This Is Their 3nd Warning!");
                                Bukkit.broadcastMessage(target.getName() + " Was Muted For 10 Minutes For Recieving 3 Warnings!");
                               
                                Bukkit.getScheduler().scheduleAsyncRepeatingTask(this, new Runnable(){
                                    public void run(){
                                        int n = 600;
                                        if(n == 0) {
                                            mute.remove(target.getName());
                                            n = 600;
                                            Bukkit.getScheduler().cancelAllTasks();
                                            target.sendMessage(prefix + ChatColor.DARK_GRAY + "You Are No Longer Muted.");
                                        }
                                    }
                               
 
                                    }, 0, 20l);
                               
                            }
                            if(mute.contains(target.getName())) {
                                p.sendMessage(prefix + ChatColor.DARK_RED + "" + target.getName() + " Is Already Muted!");
                            }
                        } else {
                            p.sendMessage(prefix + ChatColor.GRAY + "You Cannot Warn That Player!");
                        }
                       
                    } else {
                        p.sendMessage(prefix + ChatColor.DARK_RED + "Player Is Not Online!");
                    }
                   
                } else {
                    p.sendMessage(prefix + ChatColor.DARK_GRAY + "Not Enough Arguments. /Warn <Player> <Reason>");
                }
            }
        }
        return true;
    }
   
   
}

Sorry if there are many mistakes, i'm new and trying to learn.

 

xELI7E_SNIPEZx
Instead of checking if the target is online, try checking if it isn't null.

Code:java

Player target = this.getServer().getPlayer(args[1]);
if(target != null){
    //code
}