java 对于并列排名的实现

import java.util.*;
import java.util.Map.Entry;
import java.util.stream.Collectors;


class Student {
    private String name;
    private double score;
    private int age;
    private int index;

    public String getName() {
        return name;
    }

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

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Student(String name, double score, int age) {
        this.name = name;
        this.score = score;
        this.age = age;
    }

    public int getIndex() {
        return index;
    }

    public void setIndex(int index) {
        this.index = index;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", score=" + score +
                ", age=" + age +
                ", index=" + index +
                '}';
    }
}

class TestDemo {
    public static void main(String[] args) {
        List students = Arrays.asList(
                new Student("Jack", 52, 10),
                new Student("Amdy", 79.5, 10),
                new Student("Lucy", 68, 9),
                new Student("Tom", 79.5, 11),
                new Student("Jerry", 52, 8),
                new Student("Cherry", 79.5, 10),
                new Student("Sweet", 91, 12),
                new Student("Lucky", 68, 9),
                new Student("Sim", 79.5, 10),
                new Student("Solem", 65, 10)
        );
        // fun1(students);
        // System.out.println("---------------分割线---------------------");
        // fun2(students);
        // System.out.println("---------------分割线---------------------");
        // fun3(students);
        // System.out.println("---------------分割线---------------------");
        func4(students);
    }

    /**
     * 按照成绩排序 ---低级写法
     */
    public static void fun1(List students) {
        students.sort((s1, s2) -> -Double.compare(s1.getScore(), s2.getScore()));
        int index = 0;
        double lastScore = -1;

        for (Student s : students) {
            if (Double.compare(lastScore, s.getScore()) != 0) {
                lastScore = s.getScore();
                index++;
            }
            System.out.println("名次:" + index + "\t分数" + s.getScore() + "\t名字" + s.getName());
        }
    }

    /**
     * 按照成绩排序 --- 使用Java 8
     */
    public static void fun2(List students) {
        List>> list = students.stream()
                .collect(Collectors.groupingBy(Student::getScore))
                .entrySet()
                .stream()
                .sorted((s1, s2) -> -Double.compare(s1.getKey(), s2.getKey()))
                .collect(Collectors.toList());
        int index = 1;
        for (Entry> entry : list) {
            System.out.print("名次:" + index + "\t分数:" + entry.getKey() + "\t名字");
            entry.getValue().forEach((s) -> System.out.print("  " + s.getName()));
            System.out.println();
            index++;
        }
    }

    /**
     * 按照成绩排序 --- 使用Java 8；并列排名跳到下一名
     */
    public static void fun3(List students) {
        List>> list = students.stream()
                .collect(Collectors.groupingBy(Student::getScore))
                .entrySet()
                .stream()
                .sorted((s1, s2) -> -Double.compare(s1.getKey(), s2.getKey()))
                .collect(Collectors.toList());
        int index = 1;
        for (Entry> entry : list) {
            System.out.print("名次:" + index + "\t分数:" + entry.getKey() + "\t名字");
            entry.getValue().forEach((s) -> System.out.print("  " + s.getName()));
            System.out.println();
            index = index + entry.getValue().size();
        }
    }

    /**
     * 按照多条件排序 --- 使用Java 8；并列排名跳到下一名
     */
    public static void func4(List students) {
        // students.sort((h1, h2) -> {
        //     // 排名相同，年龄正序排序
        //     if (Double.compare(h1.getScore(), h2.getScore()) == 0) {
        //         return Double.compare(h1.getAge(), h2.getAge());
        //     }
        //     return -Double.compare(h1.getScore(), h2.getScore());
        // });
        students.sort(Comparator.comparing(Student::getScore).reversed().thenComparing(Student::getAge));
        // students.forEach(System.out::println);
        int index = 0;
        int count = 0;
        double lastScore = -1;
        Map rankMap = new HashMap<>(5);
        for (int i = 0; i < students.size(); i++) {
            Student s = students.get(i);
            System.out.println(s.toString() + "，lastScore：" + lastScore + "，count：" + count + "，index：" + index);
            // 如果成绩和上一名的成绩不相同,那么排名+1
            if (Double.compare(lastScore, s.getScore()) != 0) {
                lastScore = s.getScore();
                index = index + 1 + count;
                count = 0;
            } else {
                // 分数相同，如果年龄不同，排名+1
                if (Double.compare(students.get(i - 1).getAge(), s.getAge()) != 0) {
                    index = index + 1 + count;
                    count = 0;
                } else {
                    // 重复数+1
                    count++;
                }
            }
            s.setIndex(index);
            System.out.println(s.toString() + "，lastScore：" + lastScore + "，count：" + count + "，index：" + index);
            System.out.println("****************");
            rankMap.put(i, s);
        }
        for (Integer key : rankMap.keySet()) {
            System.out.println(rankMap.get(key));
        }
    }

}