Change Player Name Source code

ChangePlayerName.java

package net.rymate.ChangeName;

import java.util.logging.Logger;
import net.minecraft.server.EntityPlayer;
import net.minecraft.server.EntityTracker;
import net.minecraft.server.WorldServer;
import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.craftbukkit.entity.CraftPlayer;
import org.bukkit.entity.Player;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.event.player.PlayerQuitEvent;
import org.bukkit.plugin.PluginManager;
import org.bukkit.plugin.java.JavaPlugin;

public class ChangeName extends JavaPlugin {

    Logger log = Logger.getLogger("Minecraft");

    public void onDisable() {
        log.info(this.getDescription().getName() + "disabled!");
    }

    public void onEnable() {
        log.info(this.getDescription().getName() + "enabled!");
    }

    public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args) {
        if (!(sender instanceof CraftPlayer)) {
            sender.sendMessage("You are not a craftplayer!");
            return true;
        }
        if (sender.hasPermission("changename.change"))  {
            CraftPlayer player = (CraftPlayer) sender;
            if (args.length > 0) {
                log.info("Player "+player.getName()+" changing name to "+args[0]);
                sender.sendMessage("\u00a7eYou are now disguised as " + args[0] + "!");
                PluginManager pm = getServer().getPluginManager();
                pm.callEvent(new PlayerQuitEvent(player, "changing name"));
                player.setDisplayName(args[0]);
                setPlayerName(player.getHandle(), args[0]);
                pm.callEvent(new PlayerJoinEvent(player, "changing name"));
            } else {
                sender.sendMessage("\u00a7eWrong usage! /changename <name>");
            }
            return true;
        } else {
            sender.sendMessage("\u00a7eYou do not have necessary permission to change your name.");
            return true;
        }
    }

    /**
     * Set an EntityPlayer's name and update it to other clients
     * @param player entityplayer to change name of
     * @param newname name to set to
     * @author lahwran
     */
    public void setPlayerName(EntityPlayer player, String newname) {
        WorldServer world = (WorldServer) player.world;
        EntityTracker tracker = world.tracker;
        tracker.untrackEntity(player);
        player.name = newname;
        tracker.track(player);
    }
}

Wow...
but had you been tested it?

Wow...
but had you been tested it?

I'm sure you figured it out by now but this was made 2 months before Minecraft 1.0 came out, so it's safe to say it does not work now