package 测试;

 import java.util.Comparator;

 public class ComparatorByLength implements Comparator {   //定义比较器

     @Override

     public int compare(Object o1, Object o2) {

         String s1 = (String)o1;

         String s2 = (String)o2;

         int temp = s1.length()-s2.length();

         return temp==0? s1.compareTo(s2):temp;

     }

 }

 import java.util.Iterator;

 import java.util.TreeSet;

 public class TreeSetTest {

     public static void main(String[] args) {

         TreeSet ts = new TreeSet(new ComparatorByLength());

         ts.add("aaaaaaaa");

         ts.add("zz");

         ts.add("nbaq");

         ts.add("cba");

         ts.add("abc");

         Iterator it = ts.iterator();

         while (it.hasNext())

         {

             System.out.println(it.next());

         }

     }

 }