引用传递的实际引用（双向一对多）

//类型-子类型-商品
//只列出关联关系
class Item {
	private int iid;
	private String name;
	private String note;//父栏目类
	private Subitem subitem [];//一个父栏目有多个子栏目
	private Product product [];//一个父栏目有多个商品
	public Item(int iid, String name, String note) {
		this.iid = iid;
		this.name = name;
		this.note = note;
	}
}

class Subitem {
	private int sid;
	private String name;
	private String note;//子栏目类
	private Item item;//子栏目有一个父栏目
	private Product product [];//一个子栏目有多个商品
	public Subitem(int sid, String name, String note) {
		this.sid = sid;
		this.name = name;
		this.note = note;
}

class Product {
	private int pid;
	private String name;
	private double price;//商品类
	private Item item;
	private Subitm subitm;//有一个父栏目和子栏目
	public Product(int pid, String name, double price) {
		this.pid = pid;
		this.name = name;
		this.price = price;
	}
}