Java 8 - Karte in Liste konvertieren

Nur wenige Java-Beispiele zum Konvertieren vonMap inList

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. Zu Liste zuordnen

Verwenden Sie für eine einfache Konvertierung vonMap inList einfach den folgenden Code:

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);

    }

}

Ausgabe

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

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

Java 8 - Map To List

Für Java 8 können Sie dieMap in einen Stream konvertieren, verarbeiten und alsList zurückgeben

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);

    }

}

Ausgabe

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 - Karte in 2-Liste konvertieren

Dieses Beispiel ist etwas extrem und verwendetmap.entrySet(), umMap in 2List umzuwandeln

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);

    }

}

Ausgabe

//resultSortedKey
50
40
30
20
10

//resultValues
dragonfruit
watermelon
orange
apple

TOC

Java 8 - Karte in Liste konvertieren

Java 8 - Karte in Liste konvertieren

1. Zu Liste zuordnen

Java 8 - Map To List

3. Java 8 - Karte in 2-Liste konvertieren

Verweise

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