如何基于地图优先级重置列表

Question

在Java中，我使用了List和Map，它们包含与基于位置字段的查找相似的参数，并根据优先级重置列表。

我们怎么做呢？

import lombok.AllArgsConstructor;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Demo {

    private Map<Integer, DataConfig> getPriorityConfig() {
        // Here 1, 2... etc are priorities
        Map<Integer, DataConfig> MAP = new HashMap<>();
        MAP.put(1, new DataConfig("E", "3333"));
        MAP.put(2, new DataConfig("E", "1111"));
        MAP.put(3, new DataConfig("E", "5555"));
        MAP.put(4, new DataConfig("E", "2222"));
        MAP.put(5, new DataConfig("E", "4444"));
        return MAP;
    }

    public static void main(String[] args) {
        List<Student> students = Arrays.asList(
                new Student(4, "E4444", "John"),
                new Student(2, "E2222", "Mike"),
                new Student(1, "E1111", "Jane"),
                new Student(3, "E3333", "Victoria")
        );

        //  Arrange List based on Priority and create new List, output should be
        // here E3333 has priority-1, E1111 has priority-2, E5555 has priority-3 etc
        List<Student> newStudents = Arrays.asList(
                new Student(3, "E3333", "Victoria"),
                new Student(1, "E1111", "Jane"),
                new Student(2, "E2222", "Mike"),
                new Student(4, "E4444", "John")
        );
        // For me its  very important to processed based on priority only
    }

    @AllArgsConstructor
    static class DataConfig {
        private String type;
        private String location;
    }

    @AllArgsConstructor
    static class Student {
        private int id;
        private String location;
        private String name;
    }
}

Answer 1

我实现了如下逻辑：

List<Student> students = Arrays.asList(
                new Student(4, "E4444", "John"),
                new Student(2, "E2222", "Mike"),
                new Student(1, "E1111", "Jane"),
                new Student(3, "E3333", "Victoria")
        );

        Map<Integer, DataConfig> priorityConfig = getPriorityConfig();
        Map<String, Integer> MAP = new HashMap<>();
        // location and Pri
        for (Map.Entry<Integer, DataConfig> entry : priorityConfig.entrySet()) {
            MAP.put(entry.getValue().type + entry.getValue().location, entry.getKey());
        }

        Map<Integer, Student> integerStudentMap = new HashMap<>();
        for (Student s: students) {
            Integer integer = MAP.get(s.getLocation());
            integerStudentMap.put(integer, s);
        }
        Map<Integer, Student> collect = integerStudentMap.entrySet()
                .stream()
                .sorted(comparingByKey())
                .collect(Collectors.toMap(e -> e.getKey(), e -> e.getValue(), (e1, e2) -> e2));
        System.out.println(collect);

        List<Student> list = new ArrayList<>(collect.values());
        System.out.println(list);

Answer 2

为了实现您想要的目标，应该有一个与其优先级相匹配的地图位置(与您实际拥有的位置相反)。就像这样：

Map<String, Integer> locationPriorities = new HashMap<>();
locationPriorities.put("E1111", 1);
locationPriorities.put("E2222", 2);
// etc...

或者，如果从其他地方检索映射，仍然可以将其转换为所需的格式：

Map<String, Integer> locationPriorities =
    getPriorityConfig().entrySet()
                       .stream()
                       .collect(toMap(e -> e.getValue().location, e -> e.getKey()));

一旦有了上面的映射，排序就变得非常简单了。

您可以收集一个新的排序列表：

List<Student> newStudents =
    students.stream()
            .sorted(comparing(s -> locationPriorities.get(s.location)))
            .collect(toList());

或者对现有列表进行排序：

students.sort(comparing(s -> locationPriorities.get(s.location)));

确保导入这些静态方法(或者使用限定调用)：

import static java.util.Comparator.comparing;
import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.toMap;