order by用java怎么实现

以下是使用Java实现order by的示例代码：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class OrderByDemo {
    public static void main(String[] args) {
        // 创建一个Person列表
        List<Person> personList = new ArrayList<>();
        personList.add(new Person("Tom", 20));
        personList.add(new Person("Jerry", 18));
        personList.add(new Person("Mike", 22));
        personList.add(new Person("Lucy", 19));

        // 按照年龄升序排序
        Collections.sort(personList, new Comparator<Person>() {
            @Override
            public int compare(Person o1, Person o2) {
                return o1.getAge() - o2.getAge();
            }
        });

        // 输出排序结果
        for (Person person : personList) {
            System.out.println(person.getName() + " " + person.getAge());
        }
    }
}

class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}