java - map 流到 map

Question

如何在 Java 8 中将 Map(相同类型)的 Stream 扁平化为单个 Map？

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

Answer 1

我的语法可能有点偏离，但 flatMap 应该为您完成大部分工作:

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
}