地图流到地图 [英] Stream of maps to map

问题描述

在Java 8中，如何将Map(相同类型)的Stream展平为单个Map?

How can I flatten a Stream of Maps (of the same types) to a single Map in Java 8?

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

推荐答案

我的语法可能有些偏离，但是flatMap应该为您完成大部分工作:

My syntax may be a bit off, but flatMap should do most of the work for you :

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
}

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