Java 8 – Map转化成List

For Java 8, you can convert the Map into a stream, process it and returns it back as a List

示例代码

package com.test;

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<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 to List...");

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

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

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

        List<String> 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<String> result3 = map.keySet().stream()
                .filter(x -> !"banana".equalsIgnoreCase(x))
                .collect(Collectors.toList());

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

    }

}

输出

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