Comparator 對物件排序的優先順序的定義：

返回的數字越大排名越靠前

eg：一個物件有三個屬性，年齡，工資，銷售量

如果設定一個排序規則，

優先排序規則：
年齡從小到大、
工資從大到小
銷量從高到底

該怎麼排

下面插入程式碼，先定義一個類

class User
{
    private int age;
    
    private int salary;
    
    private int sales;
    
    public int getAge()
    {
        return age;
    }
    
    public void setAge(int age)
    {
        this.age = age;
    }
    
    public int getSalary()
    {
        return salary;
    }
    
    public void setSalary(int salary)
    {
        this.salary = salary;
    }
    
    public int getSales()
    {
        return sales;
    }
    
    public void setSales(int sales)
    {
        this.sales = sales;
    }
    
    public User(int age,int salary,int sales)
    {
        super();
        this.age = age;
        this.salary = salary;
        this.sales = sales;
    }
    
    @Override
    public String toString()
    {
        return "User [age=" + age + ", salary=" + salary + ", sales=" + sales + "]";
    }
    
}
 

寫一個測試類：

public class ComparatorTest
{
    public static void main(String[] args)
    {
        User u1 = new User(11, 22, 33);
        User u2 = new User(11, 22, 34);
        User u3 = new User(11, 22, 35);
        User u4 = new User(21, 22, 33);
        User u5 = new User(31, 22, 33);
        User u6 = new User(41, 22, 33);
        User u7 = new User(51, 220, 33);
        User u8 = new User(51, 222, 33);
        User u9 = new User(51, 226, 77);
        User u10 = new User(51, 226, 33);
        User u11 = new User(11, 22, 33);
        
        List<User> ulist = new ArrayList<User>();
        ulist.add(u11);
        ulist.add(u10);
        ulist.add(u9);
        ulist.add(u8);
        ulist.add(u7);
        ulist.add(u6);
        ulist.add(u5);
        ulist.add(u4);
        ulist.add(u3);
        ulist.add(u2);
        ulist.add(u1);
        Collections.sort(ulist, comparator);//呼叫Comparator
        for (User user : ulist)
        {
            System.out.println(user);
        }
    }
    
    public static Comparator<User> comparator = new Comparator<User>()
    {
        
        @Override
        public int compare(User o1, User o2)
        {
            // 優先排序規則：
            // 年齡從小到大、
            // 工資從大到小
            // 銷量從高到底
            int a = o1.getAge() - o2.getAge();
            if (a != 0)
            {
                return a > 0 ? 3 : -1;//
            }
            else
            {
                a = o2.getSalary() - o1.getSalary();
                if (a != 0)
                {
                    return a > 0 ? 2 : -2;
                }
                else
                {
                    return o2.getSales() - o1.getSales() > 0 ? 1 : -3;
                }
            }
        }
    };
}
}
 

輸出結果：

User [age=11, salary=22, sales=35]
User [age=11, salary=22, sales=34]
User [age=11, salary=22, sales=33]
User [age=11, salary=22, sales=33]
User [age=21, salary=22, sales=33]
User [age=31, salary=22, sales=33]
User [age=41, salary=22, sales=33]
User [age=51, salary=226, sales=77]
User [age=51, salary=226, sales=33]
User [age
 
=51, salary=222, sales=33]
User [age=51, salary=220, sales=33]

轉載：https://www.cnblogs.com/dayu007/p/7692348.html