在Java 8中递归展平嵌套映射的值

您可以定义一个递归方法来展平一个地图并将其用作函数

Stream#flatMap

例：

public class FlatMap {    public static Stream<Object> flatten(Object o) {        if (o instanceof Map<?, ?>) { return ((Map<?, ?>) o).values().stream().flatMap(FlatMap::flatten);        }        return Stream.of(o);    }    public static void main(String[] args) {        Map<String, Object> map0 = new TreeMap<>();        map0.put("key1", "value1");        map0.put("key2", "value2");        Map<String, Object> map1 = new TreeMap<>();        map0.put("key3", map1);        map1.put("key3.1", "value3.1");        map1.put("key3.2", "value3.2");        Map<String, Object> map2 = new TreeMap<>();        map1.put("key3.3", map2);        map2.put("key3.3.1", "value3.3.1");        map2.put("key3.3.2", "value3.3.2");        List<Object> collect = map0.values().stream().flatMap(FlatMap::flatten).collect(Collectors.toList());        // or        List<Object> collect2 = flatten(map0).collect(Collectors.toList());        System.out.println(collect);     }}

对于给定的嵌套地图，它会打印

[value1，value2，value3.1，value3.2，value3.3.1，value3.3.2]