TreeSet (non-repeatable, automatic sorting) for custom sorting

Method One: Let the class implement the comparable interface, and overwrite the CompareTo () method, add the custom class to TreeSet

1 ImportJava.util.Scanner;2 ImportJava.util.TreeSet;3 //TreeSet Applications4 classMain {5      Public Static voidMain (string[] args) {6Scanner s =NewScanner (system.in);7Treeset<stringdemo> set =NewTreeset<>();8          while(S.hasnextline ()) {9             intn =Integer.parseint (S.nextline ());Ten              for(inti = 0; I < n; i++) { OneString string =s.nextline (); ASet.add (NewStringdemo (String)); -             } -              for(Stringdemo s1:set) { the System.out.println (s1.getstring ()); -             } -         } - s.close (); +     } - } + classStringdemoImplementscomparable{ A     Privatestring string; at Stringdemo (String s) { -          This. String =s; -     } -      Public intcompareTo (Object obj) { -Stringdemo s =(Stringdemo) obj; -         if( This. String.CompareTo (s.string) <= 0) in             return-1; -         return1; to     } +      PublicString getString () { -         return  This. String; the     } *}

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Method Two: Customize a sequencer that implements comparator, implement the Compare () method (two comparisons), add this sequencer when creating treeset

1 ImportJava.util.Comparator;2 ImportJava.util.Scanner;3 ImportJava.util.TreeSet;4 //TreeSet Applications5 classMain {6      Public Static voidMain (string[] args) {7Scanner s =NewScanner (system.in);8Treeset<string> set =NewTreeset<> (Newstrcomparator ());9          while(S.hasnextline ()) {Ten             intn =Integer.parseint (S.nextline ()); One              for(inti = 0; I < n; i++) { AString string =s.nextline (); - Set.add (string); -             } the              for(String s1:set) { - System.out.println (S1); -             } - set.clear (); +         } - s.close (); +     } A } at classStrcomparatorImplementscomparator{ -      Public intCompare (Object Obj1, Object obj2) { -String S1 =(String) obj1; -String s2 =(String) obj2; -         if(S1.compareto (S2) <= 0) -             return-1; in         return1; -     } to}

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TreeSet (non-repeatable, automatic sorting) for custom sorting