为什么往goodsSet集合里添加不上东西

package com.imooc.shop;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class GoodsManage {
    private Set<Goods> goodsSet=new HashSet<Goods>();
    public GoodsManage(){
     
    }
 public GoodsManage(Set<Goods> goodsSet) {
  super();
  this.goodsSet = goodsSet;
 }
 public Set<Goods> getGoodsSet() {
  return goodsSet;
 }
 public void setGoodsSet(Set<Goods> goodsSet) {
  this.goodsSet = goodsSet;
 }
 //导入商品信息
 public void importGoods(){
   Goods goods1=new Goods("goods004","手机",2300.0,"android手机");
   Goods goods2=new Goods("goods002","饮水机",299.0,"带净化功能的饮水机");
   Goods goods3=new Goods("goods003","笔记本电脑",4999.0,"15寸笔记本电脑");
   Goods goods4=new Goods("goods001","水杯",56.0,"不锈钢水杯");
   goodsSet.add(goods1);
   goodsSet.add(goods2);
   goodsSet.add(goods3);
   goodsSet.add(goods4);
   System.out.println("导入成功！");
 }
 //展示所有商品
 public void displayAllGoods(){
  if (goodsSet.size() == 0) {
   System.out.println("还没有商品，请导入商品信息");
  } else {
   System.out.println("所有商品信息为：");
   Iterator<Goods> it = goodsSet.iterator();
   while (it.hasNext()) {
    System.out.println(it.next());
   }
  }
 }
}