Java 8 Lambda List to Map<Int, List<String>> -


i have list of dto following element. userseqid have duplicate values,

private int userseqid; private string firstname; private string lastname; private string acctagencynumber;

i trying use java 8 lambda group 'userseqid' map.

i want map<integer, list<string>> key should userseqid , value list of acctagencynumber.

when use 

map<integer, list<userbasicinfodto>> superuseracctmap = customersuperuserlist.stream()     .collect(collectors.groupingby(userbasicinfodto::getuserseqid));

i map<integer, list<userbasicinfodto>> key userseqid value list of whole object.

there dedicated version of groupingby() use case:

map<integer, list<string>> result = customersuperuserlist.stream()       .collect(collectors.groupingby(         userbasicinfodto::getuserseqid,         collectors.mapping(userbasicinfodto::getacctagencynumber, tolist())));

the key point of use helper mapping collector, using can override default groupingby behaviour.


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