CmdCooldownPlugin

package com.acuddlyheadcrab.testplugin;

import java.util.Date;
import java.util.HashMap;

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

public class TestPlugin extends JavaPlugin{

    public static HashMap<CommandSender, Date> lastcmdtime;
    private int cmdcooldown = 3;

    public void onEnable() {
//      make sure to load the hash map here or else you'll get an NPE
        lastcmdtime = new HashMap<CommandSender, Date>();
    }

    public void onDisable() {}

    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
//      this is just a test command
        if(cmd.getName().equalsIgnoreCase("test")){
            if(checkLastCmdTime(sender, cmdcooldown*1000)){

            } else sender.sendMessage("You must wait to do this!");
//          disadvantage here is that it doesn't return the seconds you have left to do it
        }
        return true;
    }

//  this is used to get when they will be able to use the cmd again
    public final static Date getCooldownTime(Date date, int cooldownmillis){
        return new Date(date.getTime()+cooldownmillis);
    }

//  as it says, this gets the current time via the java.util.Date class
    public final static Date getCurrentDate(){
        return new Date(System.currentTimeMillis());
    }

    /* returns true if the current time is after their required cooldown time
    * OR if they are not in the hash map yet
    */
    public static boolean checkLastCmdTime(CommandSender sender, int cooldownmillis){
        if(lastcmdtime.containsKey(sender)){
            Date cooldowntime = getCooldownTime(lastcmdtime.get(sender), cooldownmillis);
            return getCurrentDate().after(cooldowntime);
        } else
            lastcmdtime.put(sender, getCurrentDate()); return true;
    }
}