自定义List对象集合排序

1.定义实体类

public class Commodity {
    //种类、名称、价格、商家名称、月均销量
    private String type;
    private String name;
    private double price;
    private String shopName;
    private int sales;

    public Commodity() {
    }
    public Commodity(String type, String name, double price, String shopName, int sales) {
        this.type = type;
        this.name = name;
        this.price = price;
        this.shopName = shopName;
        this.sales = sales;
    }

//此处省略类属性的get   set方法

    public String toString(){
        return "名称："+this.getName()+",\t售价："+this.getPrice()+",\t卖家："+this.getShopName()+",\t月销量："+this.getSales();
    }
}

2.自定义排序的类
必须实现Comparator接口，按照类的sales销量排序
boolean 表示升序还是降序，false降序 true升序

public class SalesComparator implements Comparator {
    boolean is_Ascend;
    public SalesComparator(boolean b){
        this.is_Ascend = b;
    }

    public int compare(Commodity com1,Commodity com2) {
        if(is_Ascend) {
            return (int)(com1.getSales()-com2.getSales());
        }else {
            return (int)(com2.getSales()-com1.getSales());
        }
    }
}

3.main主程序调用sort方法

public static void main(String[] args) {
		//准备一个集合，添加一些对象
        ArrayList powedList = new ArrayList<>();
        //忽略添加对象的过程
        powedList.add...........
        
        //排序
        Collections.sort(powedList,new SalesComparator(false));
        //显示粉饼销量前3名
        System.out.println("\n粉饼分析结果如下：");
        for (int i =0 ;i