原始数据:key1, val1key1, val2key2, val3key2, val4key3, val5
想变形为:key1 => [val1, val2]key2 => [val3, val4]key3 => [val5]
该怎么写?
list<T> list;list.stream.collect(Collectors.groupingBy(T::getKey1))
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