Java 8 多字段复杂对象排序：兼顾外部依赖

public class Person {
    private int age;
    private int yearsOfEducation;

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

    public int getAge() { return age; }
    public int getYearsOfEducation() { return yearsOfEducation; }

    @Override
    public String toString() {
        return "Person{age=" + age + ", education=" + yearsOfEducation + "}";
    }
}

// 排序示例
List<Person> persons = Arrays.asList(
    new Person(26, 3),
    new Person(30, 4),
    new Person(28, 5),
    new Person(28, 5)
);

Collections.sort(persons, Comparator.comparing(Person::getAge)
                                    .thenComparing(Person::getYearsOfEducation));
// 结果将按年龄升序，年龄相同时按教育年限升序

public class Employer {
    // 假设Employer内部维护了Person到工作年限的映射
    // 实际场景可能通过数据库查询或其他业务逻辑获取
    public int getYearsOfEmployment(Person p) {
        // 模拟逻辑，实际应根据p的具体信息返回
        if (p.getAge() == 28 && p.getYearsOfEducation() == 5) {
            // 区分p3和p4
            if (p.toString().contains("p3")) return 10; // 假设p3的标识
            if (p.toString().contains("p4")) return 8; // 假设p4的标识
        }
        return p.getAge() / 3; // 示例逻辑
    }
}

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

public class SortingWithExternalDependency {

    // Person 类定义 (同上)
    public static class Person {
        private int age;
        private int yearsOfEducation;
        private String id; // 用于区分相同age和education的Person

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

        public int getAge() { return age; }
        public int getYearsOfEducation() { return yearsOfEducation; }
        public String getId() { return id; }

        @Override
        public String toString() {
            return "Person{" +
                   "id='" + id + '\'' +
                   ", age=" + age +
                   ", education=" + yearsOfEducation +
                   '}';
        }
    }

    // Employer 类定义 (同上)
    public static class Employer {
        public int getYearsOfEmployment(Person p) {
            // 模拟根据Person的ID返回不同的工作年限
            switch (p.getId()) {
                case "p1": return 5;
                case "p2": return 7;
                case "p3": return 10;
                case "p4": return 8;
                default: return 0;
            }
        }
    }

    public static void main(String[] args) {
        // 初始化数据
        Employer employer = new Employer();
        Person p1 = new Person(26, 3, "p1");
        Person p2 = new Person(30, 4, "p2");
        Person p3 = new Person(28, 5, "p3");
        Person p4 = new Person(28, 5, "p4");

        List<Person> persons = Arrays.asList(p1, p2, p3, p4);

        System.out.println("原始列表: " + persons);

        // 使用Comparator链和方法引用进行排序
        Collections.sort(persons, Comparator.comparing(Person::getAge)
                                            .thenComparing(Person::getYearsOfEducation)
                                            .thenComparing(employer::getYearsOfEmployment));

        System.out.println("排序后列表: " + persons);
        // 预期输出顺序：p1, p4, p3, p2
        // p1: age=26, education=3, employment=5
        // p4: age=28, education=5, employment=8 (比p3小)
        // p3: age=28, education=5, employment=10
        // p2: age=30, education=4, employment=7
    }
}