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import org.bukkit.Bukkit;
import org.bukkit.command.*;
import org.bukkit.entity.Player;

import java.util.ArrayList;
import java.util.List;

public class MurderCommand implements TabExecutor {


    @Override
    public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {


        if (sender instanceof Player){
            Player p = (Player) sender;

            if (args.length > 0){
                Player target = Bukkit.getPlayer(args[0]);

                target.setHealth(0);

                p.sendMessage("You just murdered another human being.");
            }
        }


        return true;
    }

    @Override
    public List<String> onTabComplete(CommandSender sender, Command command, String alias, String[] args) {
        if (args.length == 1){
            List<String> playerNames = new ArrayList<>();
            Player[] players = new Player[Bukkit.getServer().getOnlinePlayers().size()];
            Bukkit.getServer().getOnlinePlayers().toArray(players);
            for (int i = 0; i < players.length; i++){
                playerNames.add(players[i].getName());
            }

            return playerNames;
        }else if (args.length == 2){
            List<String> arguments = new ArrayList<>();
            arguments.add("Daddy");
            arguments.add("JamesHarden#1");

            return arguments;
        }
        return null;
    }
}

public final class TabAutoCompletion extends JavaPlugin {

    @Override
    public void onEnable() {
        // Plugin startup logic
        getCommand("murder").setExecutor(new MurderCommand());
    }

    @Override
    public void onDisable() {
        // Plugin shutdown logic
    }
}