Java - lagra orders i arraylist

class Customer {
    
    public ArrayList<long> orderList = new ArrayList<>();

	private String username;
	private String password;

	public Customer(String username, String password) {
		this.username = username;
		this.password = password;
	}

	public String getUsername() {
		return username;
	}

	public boolean checkPassword(String password) {
	    // Inte ett bra sätt att hantera lösenord
		return this.password.equals(password);
	}

}

class Order {
    
    private long id;
    
    public Order (long order){
        this.order = order;
    }
    
    orderList.add(Order);
}