根據成員欄位的值在另一個串列中的位置對串列進行排序

我有一個帶有欄位 score(int)、name(String) 和 country(String) 的人

1, Jane , Spain
2, James, Italy
1, John , Italy
2, Peter , England
3, Thomas , England
3, Martin , England

現在我提供另一個代表國家名稱的字串串列說： [Italy, Spain, Norway, England, Germany]

我的要求是首先根據分數對 Person 串列進行排序，如果他們具有相同的分數，則按國家名稱串列中提供的國家名稱進行排序。如果國家/地區名稱也匹配，則按人名排序。

所以最后應該按以下順序回傳人員物件：

1, John, Italy
1, Jane, Spain
2, James, Italy
2, Peter, England
3, Martin, England
3, Thomas, England

這是我正在嘗試的代碼：

public static List<Person> sortRecords(List<Person> people, List<String> countries) {
    people.sort((p1, p2) -> {
        int compare = p1.getScore() - p2.getScore();
        if(compare == 0) {
            compare = // how to compare by country names based on provided List<String> countries
            if(compare == 0) {
                compare = p1.getName().compareTo(p2.getName());
            }
        }
        return compare;
    });
}

我被困在按國名進行比較。

uj5u.com熱心網友回復：

利用 List.indexOf

public static List<Person> sortRecords(List<Person> people, List<String> countries) {
    people.sort((p1, p2) -> {
        int compare = p1.getScore() - p2.getScore();
        if(compare == 0) {
            compare = countries.indexOf(p1.getCountry()) - countries.indexOf(p2.getCountry());
            if(compare == 0) {
                compare = p1.getName().compareTo(p2.getName());
            }
        }
        return compare;
    });
    return people;
}

請注意，由于排序是就地完成的，您不需要回傳串列，然后使用 java.util.Comparator您可以做一些好事

public static void sortRecords(List<Person> people, List<String> countries) {
    people.sort(
         Comparator.comparingInt(Person::getScore)
                   .thenComparingInt(person -> countries.indexOf(person.getCountry()))
                   .thenComparing(Person::getName)
    );
}

uj5u.com熱心網友回復：

我會使用穩定的排序演算法按名稱、國家和分數對串列進行排序。見https://www.geeksforgeeks.org/stability-in-sorting-algorithms/

import java.util.*;
class Record {
    int score; String name; String country;
    Record(int s, String n, String c){ score=s; name=n; country=c; }
    public String toString(){ 
      return String.format("[%d, %s, %s]", score, name, country);
    }
}
public class Main{
    public static void main(String[] args) {
        Record[] records = {
              new Record(1, "Jane" ,   "Spain"),
              new Record(2, "James",   "Italy"),
              new Record(1, "John" ,   "Italy"),
              new Record(2, "Peter",   "England"),
              new Record(3, "Thomas",  "England"),
              new Record(3, "Martin", "England")
        };
        Comparator<Record> byScore   = (r1,r2)->r1.score-r2.score;
        Comparator<Record> byCountry = (r1,r2)->r1.country.compareTo(r2.country);
        Comparator<Record> byName    = (r1,r2)->r1.name.compareTo(r2.name);

        System.out.println("===before====");
        Arrays.stream(records).forEach(System.out::println);
        
        Arrays.sort(records, byName); 
        Arrays.sort(records, byCountry);     
        Arrays.sort(records, byScore);
        
        System.out.println("===after====");
        Arrays.stream(records).forEach(System.out::println);
    }
}

輸出

===before====
[1, Jane, Spain]
[2, James, Italy]
[1, John, Italy]
[2, Peter, England]
[3, Thomas, England]
[3, Martin, England]
===after====
[1, John, Italy]
[1, Jane, Spain]
[2, Peter, England]
[2, James, Italy]
[3, Martin, England]
[3, Thomas, England]

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