package me.vipel.main;

import me.vipel.Events.onCraft;
import me.vipel.Events.onPlayerDamage;
import org.bukkit.Bukkit;
import org.bukkit.GameMode;
import org.bukkit.Location;
import org.bukkit.block.Block;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.potion.PotionEffect;
import org.bukkit.potion.PotionEffectType;
import org.bukkit.scheduler.BukkitRunnable;
import org.bukkit.scheduler.BukkitScheduler;

public class Main extends JavaPlugin {
    boolean hasBoat = false;
    boolean isEmpty = true;
    Plugin plugin;

    @Override
    public void onEnable() {
        Bukkit.getServer().getPluginManager().registerEvents(new onPlayerDamage(), this);
        Bukkit.getServer().getPluginManager().registerEvents(new onCraft(), this);
        (new BukkitRunnable() {
            public void run() {
                Bukkit.getOnlinePlayers().forEach(p -> {
                    Location l = p.getLocation().clone();
                    if (p.getGameMode().equals(GameMode.CREATIVE) || p.getGameMode().equals(GameMode.SPECTATOR))
                        return;


                    if (p.isSwimming()) {
                        if (!(p.hasPotionEffect(PotionEffectType.SPEED))) {
                            p.sendMessage("<Notch> I see you're trying to swim, here's speed 2!");
                            p.addPotionEffect(new PotionEffect(PotionEffectType.SPEED, 19999980, 2));
                        }else {
                            p.setRemainingAir(p.getMaximumAir());
                        }
                    }else {
                        p.removePotionEffect(PotionEffectType.SPEED);
                    }


                    final Block b1 = p.getTargetBlockExact(3);
                    if (b1 != null && b1.getType().name().contains("LOG"))
                        (new BukkitRunnable() {
                            public void run() {
                                if (b1.equals(p.getTargetBlockExact(3)))
                                    b1.breakNaturally();
                            }
                        }).runTaskLater(plugin, 60L);
                    if (p.getLocation().getY() < -50.0D) {
                        p.sendMessage("<God> You didn't mean to do that right? Let me help you out");
                        l.setY(120.0D);
                        p.teleport(l);
                    }
                });
            }
        }).runTaskTimer(this, 10L, 5L);
    }}


Error:
[19:48:02 WARN]: [FunWars] Task #9 for FunWars v1.0.0 generated an exception
java.lang.IllegalArgumentException: Plugin cannot be null
	at org.apache.commons.lang.Validate.notNull(Validate.java:192) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at org.bukkit.craftbukkit.v1_16_R1.scheduler.CraftScheduler.validate(CraftScheduler.java:449) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at org.bukkit.craftbukkit.v1_16_R1.scheduler.CraftScheduler.runTaskTimer(CraftScheduler.java:181) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at org.bukkit.craftbukkit.v1_16_R1.scheduler.CraftScheduler.runTaskTimer(CraftScheduler.java:172) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at org.bukkit.craftbukkit.v1_16_R1.scheduler.CraftScheduler.runTaskLater(CraftScheduler.java:136) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at org.bukkit.scheduler.BukkitRunnable.runTaskLater(BukkitRunnable.java:79) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at me.vipel.main.Main$1.lambda$run$0(Main.java:52) ~[?:?]
	at java.lang.Iterable.forEach(Iterable.java:75) ~[?:1.8.0_251]
	at java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1082) ~[?:1.8.0_251]
	at me.vipel.main.Main$1.run(Main.java:27) ~[?:?]
	at org.bukkit.craftbukkit.v1_16_R1.scheduler.CraftTask.run(CraftTask.java:81) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at org.bukkit.craftbukkit.v1_16_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:400) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at net.minecraft.server.v1_16_R1.MinecraftServer.b(MinecraftServer.java:1061) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at net.minecraft.server.v1_16_R1.DedicatedServer.b(DedicatedServer.java:354) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at net.minecraft.server.v1_16_R1.MinecraftServer.a(MinecraftServer.java:1009) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at net.minecraft.server.v1_16_R1.MinecraftServer.v(MinecraftServer.java:848) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at net.minecraft.server.v1_16_R1.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[spigot1.16.1.jar:git-Spigot-05da6fa-75a2fb8]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_251]