 基础题（每道题约 3～5 分钟） 1. 实现商品信息类 GoodsInfo，定义属性商品编号 id、商品名称 name、商品价格 price、 商品销量 sale、商品库存 count；进行合理封装；  综合题（每道题约 5～7 分钟） 2. GoodsInfo 类中重写 hashCode 方法和 equals 方法，商品 id 相同即认为是相同商品； 3. GoodsInfo 类实现 Comparable 接口，按 id（int）值大小进行比较； 4. 创建测试类，实现以下操作 A : 使用 Tr

1. 实现商品信息类 GoodsInfo，定义属性商品编号 id、商品名称 name、商品价格 price、 商品销量 sale、商品库存 count；进行合理封装；

public class GoodsInfo {
    private int id;
    private String name;
    private double price;
    private int sale;
    private int count;

    public GoodsInfo(int id, String name, double price, int sale, int count) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.sale = sale;
        this.count = count;
    }

    // getter and setter methods
    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public double getPrice() {
        return price;
    }

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

    public int getSale() {
        return sale;
    }

    public void setSale(int sale) {
        this.sale = sale;
    }

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }
}

2. GoodsInfo 类中重写 hashCode 方法和 equals 方法，商品 id 相同即认为是相同商品；

public class GoodsInfo {
    // other code omitted for brevity

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + id;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) // check if the object is the same as this instance
            return true;
        if (obj == null) // check if the object is null
            return false;
        if (getClass() != obj.getClass()) // check if the object is not an instance of GoodsInfo
            return false;
        GoodsInfo other = (GoodsInfo) obj;
        if (id != other.id) // check if the id is not the same as the other instance's id
            return false;
        return true;
    }
}

3. GoodsInfo 类实现 Comparable 接口，按 id（int）值大小进行比较；

public class GoodsInfo implements Comparable<GoodsInfo> {
    // other code omitted for brevity

    @Override
    public int compareTo(GoodsInfo other) {
        return Integer.compare(this.id, other.id);
    }
}

4. 创建测试类，实现以下操作：

import java.util.*;

public class TestGoodsInfo {
    public static void main(String[] args) {
        // create some GoodsInfo objects
        GoodsInfo g1 = new GoodsInfo(1, "apple", 2.5, 10, 100);
        GoodsInfo g2 = new GoodsInfo(2, "banana", 1.5, 20, 200);
        GoodsInfo g3 = new GoodsInfo(3, "orange", 3.0, 30, 300);

        // test equals and hashCode methods
        Map<GoodsInfo, String> map = new HashMap<>();
        map.put(g1, "good");
        map.put(g2, "better");
        map.put(g3, "best");
        System.out.println(map.get(g1)); // output: good
        System.out.println(map.get(new GoodsInfo(1, "apple", 2.5, 10, 100))); // output: good

        // test compareTo method
        List<GoodsInfo> list = new ArrayList<>();
        list.add(g3);
        list.add(g1);
        list.add(g2);
        Collections.sort(list);
        System.out.println(list); // output: [GoodsInfo [id=1, name=apple, price=2.5, sale=10, count=100], GoodsInfo [id=2, name=banana, price=1.5, sale=20, count=200], GoodsInfo [id=3, name=orange, price=3.0, sale=30, count=300]]
    }
}