Help please

package me.taroshixela;

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

public class KYS extends JavaPlugin {

    @Override
    public void onEnable() {
        getLogger().info("Working!");



    }

    @Override
    public void onDisable(){
    }

    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {

        if (cmd.getName().equalsIgnoreCase("kys") && sender instanceof Player) {
        Player player = (Player) sender;

        player.setHealth(0);

        return true;

        }
        return false;
    }
}