使用接口、实现类、实体类、测试类的开发，创建一个 Goods商品类，结合集合实现数据的增、删、查、改操作。

import java.util.Date;

//Goods商品类
//		编号id--Integer
//		名称name--String
//		单价price--Float
//		产地publish--String
//		出厂日期pubdate--Date
//		备注说明info--String
//	IGoodsDao接口---定义方法的标准
//	GoodsDaoImpl实现类---所有的实现过程
//		新增商品
//		查询某一个商品
//		修改某个商品的单价
//		查询前5个商品
//		查询所有商品
//		删除某个商品
class Goods {
    private Integer id;
    private String name;
    private float price;
    private String publish;
    private Date pubdate;
    private String info;

    @Override
    public String toString() {
        return "Goods{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", price=" + price +
                ", publish='" + publish + '\'' +
                ", pubdate=" + pubdate +
                ", info='" + info + '\'' +
                '}';
    }

    public Goods(){

    }
    public Goods(Integer id, String name, float price, String publish, Date pubdate, String info) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.publish = publish;
        this.pubdate = pubdate;
        this.info = info;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }

    public String getPublish() {
        return publish;
    }

    public void setPublish(String publish) {
        this.publish = publish;
    }

    public Date getPubdate() {
        return pubdate;
    }

    public void setPubdate(Date pubdate) {
        this.pubdate = pubdate;
    }

    public String getInfo() {
        return info;
    }

    public void setInfo(String info) {
        this.info = info;
    }
}

import java.util.List;

public interface IGoodsDao {
    void add(Goods goods); //新增商品
    Goods selectOne(int id); //查询某一个商品
    void update(Goods goods);  //修改某个商品的单价
    List<Goods> selectAll(int num);// 查询前num个商品
    List<Goods> selectAll();//查询所有商品
    void delete(int gid);// 删除某个商品


}
   

package qf.week04;

import com.sun.xml.internal.bind.v2.model.core.ID;

import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
public class GoodsDaoImpl implements IGoodsDao {
    List<Goods> date = new ArrayList<Goods>();//数据存储

    {
        date.add(new Goods(1, "面包", 5.4f, "中国", Calendar.getInstance().getTime(), "达利园"));//初始化
    }

    @Override
    public void add(Goods goods) {
        date.add(goods);
    }

    @Override
    public Goods selectOne(int id) {
        for (int i = 0; i < date.size(); i++) {
            Goods goods = date.get(i);
            if (goods.getId() == id) {
                return goods;
            }
        }
        return null;
    }

    @Override
    public void update(Goods goods) {
        for (int i = 0; i < date.size(); i++) {
            Goods gs = date.get(i);
            if(gs.getId()==goods.getId()){
                gs.setPrice(goods.getPrice());
                break;
            }
        }
    }
            @Override
            public List<Goods> selectAll ( int num){
                List<Goods> list = new ArrayList<Goods>();
                for (int i = 0; i < (num > date.size() ? date.size() : num); i++) {
                    list.add(date.get(i));
                }
                return list;
            }
            @Override
            public List<Goods> selectAll () {
                return date;
            }

            @Override
            public void delete (int gid){
                Goods goods = selectOne(gid);
                date.remove(goods);
 }
}