1，TreeSet保证元素唯一和比较器排序的原理及代码实现

 

import java.util.Comparator;

import java.util.TreeSet;

public class Demo3_TreeSet   {



    public static void main(String[] args)  {

        //需求:将字符串按照长度排序

        TreeSet<String> ts = new TreeSet<>(new CompareByLen());        //Comparator c = new CompareByLen();

        ts.add("aaaaaaaa");

        ts.add("z");

        ts.add("wc");

        ts.add("nba");

        ts.add("cba");

        

        System.out.println(ts);

    }

class CompareByLen /*extends Object*/ implements Comparator<String> {

    @Override

    public int compare(String s1, String s2) {        //按照字符串的长度比较

        int num = s1.length() - s2.length();        //长度为主要条件

        return num == 0 ? s1.compareTo(s2) : num;    //内容为次要条件

    }

    

}