Rainbows!

Change.java

package io.github.Dinner1111.Rainbows;

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

import org.bukkit.Color;
import org.bukkit.FireworkEffect;
import org.bukkit.Material;
import org.bukkit.FireworkEffect.Type;
import org.bukkit.entity.EntityType;
import org.bukkit.entity.Firework;
import org.bukkit.entity.Player;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.FireworkMeta;
import org.bukkit.inventory.meta.LeatherArmorMeta;

public class Change {
    public int fNum = 0;
	public int index = 0;
	public List<Color> Colors = new ArrayList<Color>();
	public List<Material> leatherArm = new ArrayList<Material>();
	public LeatherArmorMeta lColor;
	public int n;
	
	public Change()
	{
		Colors.add(Color.RED);
		Colors.add(Color.BLUE);
		Colors.add(Color.AQUA);
		Colors.add(Color.LIME);
		Colors.add(Color.ORANGE);
		Colors.add(Color.YELLOW);
		Colors.add(Color.TEAL);
		leatherArm.add(Material.LEATHER_CHESTPLATE);
		leatherArm.add(Material.LEATHER_BOOTS);
		leatherArm.add(Material.LEATHER_HELMET);
		leatherArm.add(Material.LEATHER_LEGGINGS);
		ItemStack arm = new ItemStack(299, 1);
		lColor = (LeatherArmorMeta) arm.getItemMeta();
		n = 0;
	}
	
	public void colorize(Player[] p)
	{
		boolean change = false;
		lColor.setColor(Colors.get(n));
		for (Player player : p) {
			if (player.getInventory().getHelmet() != null)
				if (leatherArm.contains(player
						.getInventory().getHelmet()
						.getType()))
					player.getInventory()
							.getHelmet()
							.setItemMeta(lColor);
					change = true;
			if (player.getInventory()
					.getChestplate() != null)
				if (leatherArm.contains(player
						.getInventory()
						.getChestplate().getType()))
					player.getInventory()
							.getChestplate()
							.setItemMeta(lColor);
					change = true;
			if (player.getInventory().getLeggings() != null)
				if (leatherArm.contains(player
						.getInventory()
						.getLeggings().getType()))
					player.getInventory()
							.getLeggings()
							.setItemMeta(lColor);
					change = true;
			if (player.getInventory().getBoots() != null)
				if (leatherArm.contains(player
						.getInventory().getBoots()
						.getType()))
					player.getInventory()
							.getBoots()
							.setItemMeta(lColor);
					change = true;
			if (change == true) {
				Firework firework = (Firework) player.getWorld().spawnEntity(player.getLocation(), EntityType.FIREWORK);
				FireworkMeta fireworkMeta = firework.getFireworkMeta();
				fireworkMeta.setPower(1);
				if (fNum == 7) {
					fNum = 0;
				} else {
					switch (fNum) {
					case 0:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.RED)
								.build());
						fNum = fNum + 1;
						break;
					case 1:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.BLUE)
								.build());
						fNum = fNum + 1;
						break;
					case 2:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.AQUA)
								.build());
						fNum = fNum + 1;
						break;
					case 3:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.LIME)
								.build());
						fNum = fNum + 1;
						break;
					case 4:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.ORANGE)
								.build());
						fNum = fNum + 1;
						break;
					case 5:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.YELLOW)
								.build());
						fNum = fNum + 1;
						break;
					case 6:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.TEAL)
								.build());
						fNum = fNum + 1;
						break;
					default:
						fireworkMeta.addEffect(FireworkEffect.builder()
								.with(Type.BALL)
								.trail(true)
								.flicker(true)
								.withColor(Color.RED)
								.build());
						fNum = fNum + 1;
						break;
					}
				}
				firework.setFireworkMeta(fireworkMeta);
				change = false;
			}
		}
	}
}

plugin.yaml

name: Rainbows
main: io.github.Dinner1111.Rainbows.Rainbow
version: 1.0.0

commands:
  rainbow:
    description: Make a colorful rainbow in every aspect.
    usage: /rainbow
    permission: Rainbows.rainbow
    permission-message: Sorry, you don't have permission to make rainbows.

Rainbow.java

package io.github.Dinner1111.Rainbows;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.command.*;

public final class Rainbow extends JavaPlugin implements CommandExecutor {

    int n = 0;
	int task;
	Change c = new Change();
	boolean running = false;

	@Override
	public void onEnable() {
		getLogger().info("Rainbow has made a colorful entrance.");
		getCommand("rainbow").setExecutor(this);
	}

	@Override
	public void onDisable() {
		getLogger().info("Rainbow has run out of color.");
	}

	public boolean onCommand(CommandSender sender, Command cmd, String label,
			String[] args) {
		if (cmd.getName().equalsIgnoreCase("rainbow")) {
			if (sender.hasPermission("Rainbows.rainbow")) {
				if(!running)
				{
					running = !running;
					sender.sendMessage(ChatColor.GREEN + "Starting the Rainbow loop!");
					task = Bukkit.getServer().getScheduler()
						.scheduleSyncRepeatingTask(this, new Runnable() {
							public void run() {
								c.colorize(Bukkit.getOnlinePlayers());
								c.n++;
								if (c.n > 6)
									c.n = 0;
							}
						}, 0, 40);
				}
				else
				{
					sender.sendMessage(ChatColor.GREEN + "Stoping the Rainbow loop!");
					Bukkit.getServer().getScheduler().cancelTask(task);
					running = !running;
				}
					
			}
		}
		return true;
	}
}