要映射的地图流

Question

我怎么能展平Stream的Map(同类型)s到一个Map用Java 8？

Map<String, Long> toMap(Stream<Map<String, Long>> stream) {
    return stream. ???
}

Answer 1

我的语法可能有点偏,但flatMap应该为你完成大部分工作:

Map<String, Long> toMap(Stream<Map<String, Long>> stream) {
    return stream.flatMap (map -> map.entrySet().stream()) // this would create a flattened
                                                           // Stream of all the map entries
                 .collect(Collectors.toMap(e -> e.getKey(),
                                           e -> e.getValue())); // this should collect
                                                               // them to a single map
}