Java 8 將 Map 轉換為 List

public class ConvertMapToList {

    public static void main(String[] args) {

        Map<Integer, String> 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 as List of Integrer method 1");

        List<Integer> methodOneIntegers= map.entrySet().stream()
                .map(x -> x.getKey())
                .collect(Collectors.toList());
             
       methodOneIntegers.forEach(System.out::println);

       System.out.println("\n1. Export Map Key as List of Integrer method 2");

        List<Integer> methodTwoIntegers= map.keySet().stream()                    
                .collect(Collectors.toList());

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

        System.out.println("\n2. Export Map Value as List of String method 1");

        List<String> methodOneStrings= map.entrySet().stream()
                .map(x -> x.getValue())
                .collect(Collectors.toList());

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

    System.out.println("\n2. Export Map Value as List of String method 2");

        List<String> methodTwoStrings= map.values().stream()
                .map(x -> x.getValue())
                .collect(Collectors.toList());

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

    }

}

輸出

Export Map Key as List of Integrer method 1
50
20
40
10
30

Export Map Key as List of Integrer method 2
50
20
40
10
30

Export Map Value as List of String method 1
dragonfruit
orange
watermelon
apple
banana

Export Map Value as List of String method 2
dragonfruit
orange
watermelon
apple
banana