Java list de-weight mode and efficiency comparison

There are three ways to remove the list and ensure that the order is added:

Mode one, the use of hashset can not add duplicate data characteristics because HashSet can not guarantee the order of addition, so only as a criterion:

    Private Static void removeduplicate (list<string> List) {        HashSetnew hashset<string> (List.size ());        ListNew arraylist<string>(List.size ());          for (String str:list) {            if  (Set.add (str)) {                result.add (str);            }        }        List.clear ();        List.addall (result);    }

Mode two, using Linkedhashset cannot add duplicate data and can guarantee the addition order of the characteristics:

    Private Static void removeDuplicate2 (list<string> List) {        linkedhashsetnew linkedhashset< String>(List.size ());        Set.addall (list);        List.clear ();        List.addall (set);    }

Mode three, using the Contains method of the list to iterate through:

    Private Static void removeDuplicate3 (list<string> list) {        listnew arraylist<string> (List.size ());          for (String str:list) {            if (!  Result.contains (str)) {                result.add (str);            }        }        List.clear ();        List.addall (result);    }

Test method:

     Public Static voidMain (string[] args) {Finallist<string> list =NewArraylist<string>();  for(inti = 0; i < 1000; i++) {List.add ("Haha-" +i); }        LongTime =System.currenttimemillis ();  for(inti = 0; I < 10000; i++) {removeduplicate (list); }        LongTime1 =System.currenttimemillis (); System.out.println ("Time1:" + (time1-Time ));  for(inti = 0; I < 10000; i++) {removeDuplicate2 (list); }        LongTime2 =System.currenttimemillis (); System.out.println ("Time2:" + (time2-time1));  for(inti = 0; I < 10000; i++) {removeDuplicate3 (list); }        LongTime3 =System.currenttimemillis (); System.out.println ("Time3:" + (time3-time2)); }

Test results:

time1:451
time2:579
time3:62113

Conclusion:

It is recommended to use method one or method two way to carry out the weight

Java list de-weight mode and efficiency comparison