TreeSet（不可重复，自动排序）实现自定义排序

方法一：让类实现Comparable接口，并覆盖compareTo（）方法，将自定义的类加入TreeSet即可

 1 import java.util.Scanner;
 2 import java.util.TreeSet;
 3 //TreeSet应用
 4 class Main {
 5     public static void main(String[] args) {
 6         Scanner s = new Scanner(System.in);
 7         TreeSet<StringDemo> set = new TreeSet<>();
 8         while(s.hasNextLine()) {
 9             int n = Integer.parseInt(s.nextLine());
10             for (int i = 0; i < n; i++) {
11                 String string = s.nextLine();
12                 set.add(new StringDemo(string));
13             }
14             for(StringDemo s1: set) {
15                 System.out.println(s1.getString());
16             }
17         }
18         s.close();
19     }
20 }
21 class StringDemo implements Comparable{
22     private String string;
23     StringDemo(String s) {
24         this.string = s;
25     }
26     public int compareTo(Object obj) {
27         StringDemo s = (StringDemo)obj;
28         if(this.string.compareTo(s.string) <= 0)
29             return -1;
30         return 1;
31     }
32     public String getString() {
33         return this.string;
34     }
35 }

方法二：自定义一个实现Comparator的排序器，实现compare（）方法（两个一起比较），在创建TreeSet的时候将此排序器加入即可

 1 import java.util.Comparator;
 2 import java.util.Scanner;
 3 import java.util.TreeSet;
 4 //TreeSet应用
 5 class Main {
 6     public static void main(String[] args) {
 7         Scanner s = new Scanner(System.in);
 8         TreeSet<String> set = new TreeSet<>(new StrComparator());
 9         while(s.hasNextLine()) {
10             int n = Integer.parseInt(s.nextLine());
11             for (int i = 0; i < n; i++) {
12                 String string = s.nextLine();
13                 set.add(string);
14             }
15             for(String s1: set) {
16                 System.out.println(s1);
17             }
18             set.clear();
19         }
20         s.close();
21     }
22 }
23 class StrComparator implements Comparator{
24     public int compare(Object obj1, Object obj2) {
25         String s1 = (String) obj1;
26         String s2 = (String) obj2;
27         if(s1.compareTo(s2) <= 0)
28             return -1;
29         return 1;
30     }
31 }