this is the error:
package me.red888red;

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

public class Healer extends JavaPlugin{

@Override
public void onEnable() {
}

@Override
public void onDisable() {

}

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

if (cmd.getName().equalsIgnoreCase("Health") && sender instanceof Player){

Player player = (Player) sender;

player.sendMessage("Your Health is: " + player.getHealth() + "!");

int length = args.length;

if (length == 1) {

for (Player playerToHeal : Bukkit.getServer().getOnlinePlayers()) {
if(playerToHeal.getName().equalsIgnoreCase(args[0]))

{ player.sendMessage("This Players Health is " + playerToHeal.getHealth() + "!"); }

}

}

return true;

}

return false;

}

}