public class TaskHandler {

    //Static Objects
    private static TaskHandler instance;

    //Static Methods
    public static TaskHandler getInstance() {
        if (instance == null) instance = new TaskHandler();
        return instance;
    }

    //Objects
    private ArrayList<Task> taskList;
    private ArrayList<Task> addList;
    private ArrayList<Task> removeList;

    private int taskID;
    private boolean update;

    //Constructor
    public TaskHandler() {
        taskList = new ArrayList<Task>();
        addList = new ArrayList<Task>();
        removeList = new ArrayList<Task>();

        taskID = 0;
        update = false;

        initTask();
    }

    //Object Methods
    private void initTask() {
        taskID = Bukkit.getScheduler().scheduleSyncRepeatingTask(Task.plugin, new Runnable() {
            @Override
            public void run() {
                if (update) {
                    for (Task task: addList) {
                        taskList.add(task);
                    }
                    addList.clear();

                    for (Task task: removeList) {
                        taskList.remove(task);
                    }
                    removeList.clear();

                    update = false;
                }

                for (Task task: taskList) {
                    task.updateTicks();
                }
            }
        }, 0, 1);
    }

    private void cancelTask() {
        Bukkit.getScheduler().cancelTask(taskID);
    }

    public void addTask(Task task) {
        addList.add(task);
        update = true;
    }

    public void removeTask(Task task) {
        if (!taskList.contains(task)) return;
        removeList.add(task);
        update = true;
    }
}