Java 8 - Convertir la carte en liste

Quelques exemples Java pour convertir unMap enList

Map map = new HashMap<>();

// Convert all Map keys to a List
List result = new ArrayList(map.keySet());

// Convert all Map values to a List
List result2 = new ArrayList(map.values());

// Java 8, Convert all Map keys to a List
List result3 = map.keySet().stream()
    .collect(Collectors.toList());

// Java 8, Convert all Map values  to a List
List result4 = map.values().stream()
    .collect(Collectors.toList());

// Java 8, seem a bit long, but you can enjoy the Stream features like filter and etc.
List result5 = map.values().stream()
    .filter(x -> !"apple".equalsIgnoreCase(x))
    .collect(Collectors.toList());

// Java 8, split a map into 2 List, it works!
// refer example 3 below

1. Mapper vers la liste

Pour une simple conversion deMap enList, utilisez simplement le code ci-dessous:

ConvertMapToList.java

package com.example;

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

public class ConvertMapToList {

    public static void main(String[] args) {

        Map map = new HashMap<>();
        map.put(10, "apple");
        map.put(20, "orange");
        map.put(30, "banana");
        map.put(40, "watermelon");
        map.put(50, "dragonfruit");

        System.out.println("\n1. Export Map Key to List...");

        List result = new ArrayList(map.keySet());

        result.forEach(System.out::println);

        System.out.println("\n2. Export Map Value to List...");

        List result2 = new ArrayList(map.values());

        result2.forEach(System.out::println);

    }

}

Sortie

1. Export Map Key to List...
50
20
40
10
30

2. Export Map Value to List...
dragonfruit
orange
watermelon
apple
banana

Java 8 - Mapper vers la liste

Pour Java 8, vous pouvez convertir lesMap en flux, les traiter et les renvoyer sous forme deList

ConvertMapToList.java

package com.example;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class ConvertMapToList {

    public static void main(String[] args) {

        Map map = new HashMap<>();
        map.put(10, "apple");
        map.put(20, "orange");
        map.put(30, "banana");
        map.put(40, "watermelon");
        map.put(50, "dragonfruit");

        System.out.println("\n1. Export Map Key to List...");

        List result = map.keySet().stream()
                .collect(Collectors.toList());

        result.forEach(System.out::println);

        System.out.println("\n2. Export Map Value to List...");

        List result2 = map.values().stream()
                .collect(Collectors.toList());

        result2.forEach(System.out::println);

        System.out.println("\n3. Export Map Value to List..., say no to banana");
        List result3 = map.keySet().stream()
                .filter(x -> !"banana".equalsIgnoreCase(x))
                .collect(Collectors.toList());

        result3.forEach(System.out::println);

    }

}

Sortie

1. Export Map Key to List...
50
20
40
10
30

2. Export Map Value to List...
dragonfruit
orange
watermelon
apple
banana

3. Export Map Value to List..., say no to banana
dragonfruit
orange
watermelon
apple

3. Java 8 - Convertir la carte en 2 listes

Cet exemple est un peu extrême, utilisemap.entrySet() pour convertir unMap en 2List

ConvertMapToList.java

package com.example;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

//https://www.example.com/java8/java-8-how-to-sort-a-map/
public class ConvertMapToList {

    public static void main(String[] args) {

        Map map = new HashMap<>();
        map.put(10, "apple");
        map.put(20, "orange");
        map.put(30, "banana");
        map.put(40, "watermelon");
        map.put(50, "dragonfruit");

        // split a map into 2 List
        List resultSortedKey = new ArrayList<>();
        List resultValues = map.entrySet().stream()
                //sort a Map by key and stored in resultSortedKey
                .sorted(Map.Entry.comparingByKey().reversed())
                .peek(e -> resultSortedKey.add(e.getKey()))
                .map(x -> x.getValue())
                // filter banana and return it to resultValues
                .filter(x -> !"banana".equalsIgnoreCase(x))
                .collect(Collectors.toList());

        resultSortedKey.forEach(System.out::println);
        resultValues.forEach(System.out::println);

    }

}

Sortie

//resultSortedKey
50
40
30
20
10

//resultValues
dragonfruit
watermelon
orange
apple

TOC

Java 8 - Convertir la carte en liste

Java 8 - Convertir la carte en liste

1. Mapper vers la liste

Java 8 - Mapper vers la liste

3. Java 8 - Convertir la carte en 2 listes

Références

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